Green Garden Dreams

The Joy of San Diego Vegetable Gardening

How-To Articles

There’s always more to learn about gardening and the fascinating world of plants. Get tips, advice and knowledge about horticulture, with thoughtful and practical how-to articles.

1. Starting Vegetables From Seed
2. Fall Vegetables in San Diego
3. Soil In Depth
4. The Ebb & Flow Method of Hydroponics

Fall Vegetables for San Diego

Last modified on 2020-07-21 01:01:39 GMT. 6 comments. Top.

Fall in San Diego begins subtly. It’s not a dramatic burst of color like in the East Coast or other temperate climes, but rather a shifting in light and temperature – how it feels outside. That’s how it strikes me as a native. I always know when it’s Fall.

Click here to jump to the Vegetable Planting Schedule for Southern California!

Bok Choy

Bok Choy (volunteer)

August, September and October is a time when you can start to dream about what you want to plant for the Fall and Winter season , and put some seeds in pots or directly in your garden.

Here in San Diego with our mild Mediterranean climate, we are blessed with all-year-around growing. Fall is our “second spring” as far as planting goes. And when the rains come in early winter the local grasses and native plants will start to green up the golden areas of summer.

Now that the season is changing to progressively cooler, shorter days and less intense sunlight, we transition to cool-weather crops. Warm weather crops like corn, tomatoes and squash – plants that develop fruits that we eat – require long warm days and a long growing season. Cool season crops are generally plants where we eat the leaves, stems, roots or immature flowering parts, such as lettuce, kohlrabi, carrots, broccoli and so forth.

It’s a good idea to take this opportunity to add to your soil: spade it and work in some organic matter. It’s been depleted from the summer’s growing. Add some compost and/or manure, and ideally a balanced organic vegetable fertilizer to it (the fertilizer helps to compensate for the mulch that hasn’t broken down into nutrients yet). Water your plot  and let the soil settle for a couple of days; then sow your seeds. Water them gently: most winter crop seeds are small, should be planted at a shallow depth, and can wash away easily.

Planting Period Key

Optimal - Fruiting type (mostly summer vegs.)
Acceptable - (mostly summer vegs.)
Optimal - Greens type (mostly Fall/Winter vegs.)
Acceptable - Greens type (mostly Fall/Winter vegs.)
Optimal - Root type (mostly Fall/Winter vegs.)
Acceptable - Root type (mostly Fall/Winter vegs.)
The key on the right will help you interpret the vegetable planting guide table below.
The general pattern of summer veggies is that they are warmth-loving plants, grow quickly, and yield fruit of some type. Obvious examples are tomatoes (which I used as the key icon for summer types), corn, beans, squash, cantaloupes, etc. In contrast, most Fall and Winter vegetables are ones that you grow for their leaves or roots, such as lettuce, cabbage-family veggies, mustard greens, and root crops like turnips and rutabagas.

Of course there are exceptions to the “rule” for summer fruiting crops, such as Fava Beans (Broad Beans), which prefer cooler temperatures. Some leaf or root crops can be grown any time in Southern California, such as Swiss Chard and Carrots.

Southern California Vegetable Planting Schedule

Beans (bush)
Beans (pole)
Brussel Sprouts
Fava Beans
Lima Beans
Squash (summer)
Squash (winter)
Swiss Chard

That should be plenty to choose from!

If you’re curious about Fava Beans: “In mild-winter regions sow broad beans in early autumn for winter harvest (from Harvest to Table website).”:  How to Grow Broad Beans

And if you don’t want to plant veggies and just want to over-winter your plot, consider doing a favor to the soil and plant “green manure” such as alfalfa or Fava Beans. This will contribute nitrogen and help the soil community.



Rutabaga, nadmorska variety

Rutabaga, nadmorska variety

Fava Beans:

Fall can be a 2nd spring for planting” (Union Tribune Newspaper, October 22, 2006)

*Here’s a table from for Southern California with a slightly shifted schedule (October instead of September for most things)

Vegetable Garden Planting Guide For San Diego County” – Master Gardeners San Diego  / U.C. Cooperative Extension (PDF file).

Veggie Gardening in the Fall? – San Diego’s Unique Growing Season

“Veggie Gardening in the Fall? – San Diego’s Unique Growing Season”

* From a flier from Walter Andersen Nursery.

Starting Vegetables From Seed

Last modified on 2018-08-04 15:38:26 GMT. 0 comments. Top.


Starting vegetables, or any plant, from seed is a joy and a wonder. Watching plants grow from seed is amazing and fun. To take this tiny dry little bit of matter (and every kind of seed is a different shape and color), give it water and soil, and watch new green life emerge from it, is truly a beautiful thing (click to enlarge)*:

Beans Emerging in Morning Sun 07/24/'11

Royalty Purple Pod Beans Emerging in Morning Sun 07/24/'11

You can also save a lot of money by starting your own plants from seed.

What Every Plant Needs

Most people know that plants need light, water, nutrients and air. But many people don’t know that roots breathe, and need lots of air (oxygen, carbon dioxide, nitrogen) to live and grow. This is also true for seeds and seedlings – perhaps more so.

This fact became very clear to me when I grew vegetables and herbs hydroponically (“soilless gardening”) in a very loose volcanic rock, and saw how quickly and vigorously plants grew. I was also using a “fill and drain” method which pulls air down into the root zone as the nutrient solution drains out of the bed.

Professional growers and advanced hobbyist growers sometime use a propagation method for cuttings called aeroponics, that is specifically designed to provide high levels of oxygen to the root zone.

What Kinds of Vegetables are Good to Start from Seed (in Pots or Indoors) and Transplant to the Garden?

The short answer is, types that have small seeds and take a longer time to get started, or need an early start. You can grow them in small pots like peat pots or 6-packs and set them out. It’s useful to plant them in pots such as peat pots (which can be put directly in the ground) if you want an early start on the season or want to baby them to maximum health (the right amounts of water, light, temperature, etc.)
Examples include tomatoes, peppers, broccoli, and herbs.

What Kinds of Vegetables are Not Good to Start from Seed and Transplant?

The short answer is, types that are sensitive to being transplanted, or have large seeds and grow quickly.
Examples of root-sensitive vegetable plants are radishes and corn. Radishes have very long and delicate root hairs that are easily damaged. Root hairs are the super fine, single cell roots that grow from the main root, and that absorb water and nutrients from the soil. If they are disturbed or damaged, the plant cannot absorb water and nutrients and will suffer or die.

Root Hairs of a Radish Sprout

Root Hairs of a Radish Sprout


It’s best that a vegetable plant be allowed to grow quickly and continuously, without any major “stops” to it’s growth.

Vegetables with large seeds like beans and squash are better planted directly in the garden where they can grow without stops to their growth. There’s usually no reason to start them early indoors in Southern California. They can be grown in pots before being transplanted, but they need to be large seed-starting pots to give the large vigorous roots room to expand. However it’s better to plant them directly in the ground, unless they need a head start (because of the season).
Beans are of tropical origin and need the soil to be warm, or the seed will rot in the soil (it’s happened to me), especially if it’s soil with a lot of clay. Clay holds a lot of water and has extremely small particle size, so does now allow the soil to “breathe” as well as a coarser soil.

What Containers To Plant Seeds In

Clean containers and sterile soil. Fungus is the enemy of seeds and sprouts. Peat pots are an excellent choice because they can be planted directly in the ground and minimize transplant shock (it’s still best to use some B1 though, and there will probably be roots sticking out from the sides and bottom of the pot). Make sure they are new peat pots, or sterilize old ones with boiling water.

How Deep to Plant Seeds?

About 3 times the width of the seed is a general guideline that you will hear a lot. So very fine herb seeds for instance, need to be quite close to the surface. If you were to plant mint seeds for instance, which are extremely small, you would merely sprinkle them on the surface of the soil, then sprinkle some sterile, sifted seed starting mix over them, or perlite & vermiculite -just enough to barely cover them.

If a large seed is too close to the surface, the roots will not be able to get a purchase within the soil, be too exposed, and the young stem and seed head will not get established deep enough. A seed planted too deep will either not be able to reach the surface, or expend too much energy getting there.

Seed packets will tell you on the back how deep to plant the seeds, and how far apart to plants them, as well as how far apart they should be thinned to once they start growing. You can also find guides online, like here.


Keep seeds damp, but be careful not to wash them away or disturb the soil. One way to do this is to water from the bottom, so the water is wicked up. You can also use a fine spray or small stream of water, or water from the side. Seeds and sprouts (and all plants for that matter) need air as well as water in the root zone, or they can’t breathe. Also, fungi are more prone to grow on a seed if it’s wet but without enough air. Therefore be careful not to overwater, and use soil that is loose, such as with lots of organic matter, perlite,  (in the case of potting soil), and not compacted. Of course, you definitely do not want them to dry out – that would be the end of your delicate sprouts – so it’s a balance between air, water, soil, temperature, and light (radiation) intensity.

Light and Temperature

It’s very important that seedlings have enough light, and the right kind of light, so they are strong, and don’t get spindly (technically known as etiolated). Put them in a South-facing window (careful if they are under a plastic dome or wrap as they can overheat) or under lights if they are indoors. Use fluorescent, not incandescent. Fluorescent lights and LED plant lights have the proper light frequencies. Incandescent lights have too much red and infrared light and plants will get spindly. They need to be close to the fluorescent lights, roughly between 8 and 16 inches. But not too close or they will get burned.

Seeds need some warmth to sprout. Different seeds have different temperature requirements. Plants of more tropical origin like more warmth. Some examples are tomatoes, peppers and beans. You can use an electric seed warming mat if the temperature of your room or greenhouse is too cold. Sometimes the mat can make it too warm so you might want to use a book or stack of newspapers between the warming mat and the bottom of your seedling tray for insulation.


Use very dilute fertilizer after the first true leaves appear. The seeds leaves (or seed, in the case of such plants as corn and Scarlet Runner Beans) have stored food in them.


The important things to remember about transplanting are to lessen the shock for the plant, and increase it’s chance for a large and healthy spurt of growth into full vegetable-hood. When you move a plant from where it was growing, several things can potentially change: the light conditions (strength and color), the humidity, the temperature, the daylength, and possibly the chemistry of the soil and watering conditions.

For example, if you move a plant from growing indoors under fluorescent lights, to outdoors under full sunlight, that is a major change for the little plant-ling. You might want to give it a little shade, like some shade cloth or screen, or whatever you have, until it adjusts.

In some parts of the country, plants are started indoors until the weather warms up, to get a jump on the growing season. Once they are put out into the garden, they can be given help to adjust. Almost anything that allows light and air in but gives the plant some insulation at night will work. Examples include a 5-gallon water bottle with the bottom cut off

To help the roots adapt to their new soil environment, and lessen “transplant shock”, many people recommend using vitamin B1 (the kind for plants, gotten from nurseries).


Although it may seem obvious, sometimes the obvious needs to be stated. Plants need to room to grow, and if the roots and leaves are too crowded, too close to other plants, the plant “knows” this. It’s important to the plant because there is limited water and nutrients in a given area of soil, and limited air and sunlight in a given patch of earth.

It’s better to have fewer, healthier plants, than more, crowded plants. Plants that are crowded tend to be less healthy and therefore more prone to pests, and not living up to their genetic potential and will produce smaller fruits, seeds, roots, or whatever you are aiming to harvest. They won’t look  as nice too.

Thinning spacing is given on the seed packets. If you don’t have a packet, look it up, or just imagine how large the plants will be as they grow. You can always thin then more later, so don’t overdo it (like a haircut – you can always cut more but it’s hard to put hair back on!). That being said, it’s better to give a plant more space earlier – space to spread it’s wings as it were – than to wait.

* Here’s the same sprouts from the beginning of the article in the evening of the same day:

Beans Emerging Evening 7/24/'11

Royalty Purple Pod Beans Emerging Evening 7/24/'11

Here’s where I planted them – next to the corn so it can grow up the corn, as the corn grows (corn, beans, squash: the “Three Sisters” in Native American Gardening). Can you see the bean seeds in their little hollows in the earth, waiting to be covered with some soil? (I love the colors in the corn leaves in this shot):

Bean Seeds Next to Corn  7/19/'11

Bean Seeds Next to Corn 7/19/'11

Some Links

Starting Seeds Indoors-Is it worth it?

Planting Vegetable Seeds (University of California / Alameda County Master Gardeners)

Healthy Soil for Healthy Vegetables

Last modified on 2014-05-19 17:55:20 GMT. 0 comments. Top.

Soil is a deep topic (no pun intended). Soil is very complex because it’s got a biological community, and has both a mineral and an organic component. But, it can be relatively easy to take care of, because a healthy balanced soil takes care of itself, and you just have to give the soil (and the plants) what they need: inputs of organic material, water and air, and understanding what the soil needs and the plants need.

Soil preparation and upkeep is essential for a good garden. By creating healthy soil, you create a place where the cycles of life take place: you help process organic materials into nutrients, you help the soil and create a root zone for organisms below ground and above ground, with plants that turn carbon dioxide into oxygen, create beauty and food for you and visitors and dwellers in the garden. From the butterflies, birds and insects above ground, to the earthworms and microbes under the soil, you are doing your small part to create a healthier, happier, more sustainable planet.

I’ve been growing plants, including vegetables (my favorite thing to grow) since I was about 10 years old. Over that time I’ve gotten a definite impression of what plants like, and how they survive. I’ve also done some reading about plants and botany that’s provided background theory to helps me understand what I see. I’ve also spent time in nature, such as in the desert, and been impressed by the strategies plants employ to keep alive, grow and reproduce, even under very challenging conditions. I’ve also grown very unusual plants, like the carnivorous Venus Flytrap, and various Sundews and Pitcher Plants, whose form and function are evolved in response to the nutrient-poor acidic soils in which they live. These strategies and adaptations point to their basic needs.

For example, for plants growing in very arid conditions of a desert, where drying winds, sandy soil, intense sun radiation, and high temperature all conspire to rob plants of moisture, one can see where a limiting factor such water determines the way in which plants and live (and animals too), both in relation to each other and to the environment. In such an environment, the conservation of water, and protection from predations are paramount. There is more than enough solar radiation. Therefore you see all kind of protective mechanisms to help the plant keep from drying out and being eaten: hairs, thorns, waxy coatings, small leaves (or no leaves), pungent chemicals, and so forth. You also see a large distance between plants, since resources of water and nutrients are limited.

For best vegetable success, you want as few stops to their growth as possible. And ideally, you want plants to reach their greatest genetic potential. You want as few *limiting factors* as possible.

I’ll go over several factors, including air, water and minerals, but start with one real-world experience ground us (no pun intended). It has to do with air in soils. My experience growing vegetables and herbs using hydroponics was very telling. Growing gardens in both a “fill-and-drain” hydroponic bed and an organic double-dug bed, and seeing how well they did, and reading that plants like lots of air in the root zone (there’s even a system of hydroponics called Aeroponics), helped make sense of what I was seeing. Because in both cases, plants grew exceptionally fast and large, when there was lots of loose material that allowed air into the soil. With hydroponics you have a very course “soilless” medium (in my latest hydro garden it was volcanic rock: white pumice) that allows lots of oxygen into the root zone, and a nutrient solution (water with dissolved minerals) that pulls air down into the medium as it drains. And with organic methods (“biointensive”) double digging, you create a very loose pile of soil, full of coarse organic material that also creates lots of spaces for air to penetrate into the soil.

Let’s look at the big picture. In nature, every basic need is also a potential limiting factor. These limiting factors determine the pattern of life in a particular environment.
For instance, in a jungle, the limiting factors for plants are space, niche competition, sunlight below the canopy, and the fact that most nutrients are held within the biomass, so the soil is very poor. There is an abundance of water, humidity and warmth.
In a desert the limiting factor is water and nutrients. There is an abundance of sunlight, air and space.
In a wet bog the limiting factor are nutrients (too much water and low PH limit them). There is an abundance of water and sunlight.

So getting back down to soil, plants need, and soil provides (and are potentially limits), via the root zone:
• Water
• Air
• Nutrients
• A support via a stratum or medium to anchor their roots
• A biotic community and Symbiosis with fungi (mycorrhiza) and bacteria (e.g. in Nitrogen-fixing nodules in legumes)
Soil also plays a role in:
• Defense against disease and predation.
• Proper temperature, thermal regulation, and protection from solar radiation (depending on the plant)

Soil does this via:

• Water
Flows through or is held, clinging to particles, or trapped in clay, or wicks up and through.

• Air
Space between soil particles
Water that carries dissolved Oxygen

• Nutrients & Support
Inert, Inorganic compounds – minerals
Un-dissolved minerals: sand, clay, rocks that provide support and transport
Dissolved minerals: salts and ions that provide nutrients (from both inorganic and organic sources)
Organic Materials and Compounds
Plant and animal material in various stages of decomposition
Miscellaneous enzymes and organic molecules provided by the biotic community and the plant roots themselves.

Organic materials provide:
Nutrients: Microorganisms – Bacteria and fungi breakdown, provide elements in the form of ions. The cycle of life.
A whole community lives in soil: worms, bacteria (good, mostly), fungi, nematodes, sowbugs, etc. A teaspoon of productive soil generally contains between 100 million and 1 billion bacteria, representing thousands of species.
The ability to hold water.

Inorganic components provide:
Nutrients. Some minerals (rocks, originally) can form dissolved salts and ions that plants need.
Water retention. Ranges of particle size and their properties:

Clay and silt hold moisture and nutrients well but do not allow air into the root zone. Clay also holds the water so tightly (microscopic particles) that it is not available to plants. They have very poor drainage.

Sand holds less moisture and nutrients but provides good drainage. Same for rocks but even more so. Some plants need more drainage than others. For instance, cacti that evolved in habitats with sandy, rocky soils need soil that allows excellent drainage with very poor nutrient level. They grow very slowly. However they do need some organic material or nutrients. Epiphytes – plants that grown on trees for support, have roots that cling to a surface and get moisture and air directly from the air and dissolved nutrients from rain water that carries nutrients to them. At the other end of the spectrum, some plants that grow in swamps have ways of getting air in the root zone since their roots are underwater. Most plants, including vegetables, are somewhere between those two extremes, and grow best in a soil that provides good moisture retention but also provides good air and nutrient creation and transport. This generally means a soil rich in organic material, with enough inorganic material such as sand to provide better texture and drainage. A soil that was pure compost for example, would grow nice plants for a while, but would eventually become too dense as the material decomposed more, not breathing well, not allowing air and water to flow easily enough. This is why packaged potting soil always have some kind of mineral components such as sand or perlite in addition to the organic components such composted bark or peat moss. They tend to lack adequate sand though because it’s heavy to ship.

So a good soil has the proper balance of: texture, mineral and organic material (dead or dying plants and animals), a healthy biotic community, water and air, pH (roughly between 6.5 and 7.0 for most veggies). Soil also needs to be the proper temperature for whatever species you are sprouting or growing. For example, bean seeds need warm soil to germinate. Otherwise they will rot in the soil.
Good soil is sustainable, via added organic material over time, and a healthy biotic community, and rotation practices.

San Diego soils, having derived from ocean and river sediments, often contain a lot of clay and sand. There are often many rocks, usually the rounded ones that have been shaped by water erosion. The topsoil of the native chaparral habitat is generally thin. These factors mean you will want to add lots of organic material, such as compost to the soil, and of course remove the rocks. You will probably need to add more every year before planting, and sometimes as a supplement during the season. Worm castings are also a good organic source of nutrients, as are organic fertilizers.
Inorganic fertilizers do not help build the soil, being just mineral salts. They give the plants a quick boost, but then they become dependent on them. Over time they can make the soil more depleted.

So you can see that for many reasons, helping your garden by fostering a healthy balanced soil is good for the plants, the your own, health, and the earth. Enjoy the creative process and watch the miracle of life unfold in your own garden.

The Ebb & Flow Method of Hydroponics

Last modified on 2017-01-30 00:02:38 GMT. 4 comments. Top.


Soil is very complex. It’s an entire living community, forming a whole web, with trillions of microorganisms such as bacteria, fungi, as well as worms and arthropods (insects etc.) that break down the organic material, in concert with the enzymes from the roots of plants, to convert it to nutrients like Potassium, Phosphorus and Nitrogen. These basic elements are absorbed as ions, via water, by plant roots.

All plants need 16 elements to grow. They are C, H, O, N, P, K, Ca, Mg, S, Zn, Cu, Fe, Mn, B. Mo and C1. Some elements are derived from the atmosphere. Plants breathe in CO2, Carbon dioxide, and through the miracle of using sunlight, water, chlorophyll, turn it into food, such as sugars and starches (carbohydrates) and proteins for themselves and animals. Plants however cannot directly utilize Nitrogen, which is needed to make proteins and amino acids and countless other chemicals found in plants.

Organic material such as wood and dead leaves contains Nitrogen and other basic elements, but they cannot be absorbed directly by plants: they need the help of fungi, bacteria and other consumers to process dead plant, animal and minerals and turn them into plant food for green plants. Complex substances from dead plants and animals like proteins and fibers have to be broken down with the help of this community of organisms to make those bound-up elements available to green plants. It turn, the green plants provide food for the community in the soil (and on land and air!) in a continuous cycle of living metabolic activity, powered by cosmic energy from our star the Sun.

In hydroponics, we are in a sense short-circuiting this process, taking a direct approach and giving plants those nutrients, and only those nutrients, those ions in water directly, and abundantly.

The word “hydroponics” comes from the Greek words “hydro” meaning “water”, and “ponein”, “to labor or toil”. The first experiments in finding out what plants actually need – the elements of the period table (N,P,K, just as you see on any fertilizer package) – were done in pure water, with no soil, and mineral salts such as Potassium nitrate added to form ions of the elements that plants could absorb.

Hydroponics is part of “controlled environment agriculture”, based on the knowledge of optimum conditions for plant growth that have been isolated and identified. Systems are created to give the plants directly and exactly what they need for maximum growth. Very high growth rates, large size, and healthy plants with no pests or diseases are often the result of using hydroponics. There are few pests because healthy plants have a natural immunity. Pests attack weak plants, and properly grown hydroponic plants are very strong.

Other aspects of controlled environment agriculture include greenhouses, where temperature, humidity, air circulation (and even gas composition) can be controlled to some degree to help optimize conditions for year-round growing. Hydroponics in particular started with the discovery that plants could be grown in water and derive the mineral nutrition they require with a precise feeding of mineral salts to supply the roots with their required elements. Since that discovery, many variations of hydroponics have been invented, including organic hydroponics. However, they all use the basic method of using water, rather than soil to deliver nutrition to the roots.


    Solution Culture – plants are grown in straight nutrient water solution with no “soil” for support:
          Static (aerated or not)
               1. Raft Solution Culture
              2. N.F.T. (Nutrient Film Technique / Continuous Flow)
              3. Aeroponics

    Medium Culture – plants have a supporting medium physically acting like soil:
              4. Wick System
              5. Drip Systems Recovery / Non-Recovery
              6. Ebb & Flow

A PDF that explains these six basic techniques can be accessed here.

The Ebb & Flow (also known as Fill and Drain) technique of growing plants hydroponically is a low-tech method that has been around for many years. The advantages are simplicity, relatively low investment, and reliability. It does not take any fancy equipment, just a bit of initial work to set up the system. Once it’s set up, you will get tremendous growth, and can grow a very wide variety of plants, large and small, because it mimics an ideal soil medium. It also provides a support for larger plants. I’ve grown everything from lettuce to corn, tomatoes, peppers, squash, broccoli, and many kinds of herbs. One of the advantages is the amount of air exchange with the roots. Plants grow vigorously with the good gas exchange that happens with this method, and are able to get high levels of water and nutrients from the medium.

The basic idea is very simple. A tray or bed is filled with a course growing medium. A nutrient solution gets pumped into a growing tray, almost to the top of the medium. Excess water drains out of the drain stop, recirculating for a short time until the pump switches off. Once the pump is off, the nutrient drains out, leaving the medium flush with nutrients and water, and pulling air down into the medium (the root zone) in the process. This is done generally twice a day but can be at whatever regular interval is required. With highly water-retentive media in relatively cool conditions, watering only once a day is enough. By contrast, something like a gravel system, which does not retain as much moisture, could be flooded every hour in warm weather.

OK, so let’s go over all the basic components.

First you need a growing bed. Something that is watertight. The bed in the photo at the top of this article was made from wood and lined with fiberglass. It also needs to be strong enough to hold up the weight of water and a growing medium. A growing medium (the “rocks”) is what holds the plants up.

A Hydroponics Growing Bed or Tray

Deeper beds are better for larger plants. Roughly 4 to 8 inches is usually enough. The growing bed in the photo at the top might have been deeper, because I used 2 by 12 planks of wood for the sides (which are actually 1.5″ x 11.25″).

Almost any container or tray that will hold water and a growing medium can be used. I’ve used various kinds of ready-made trays found at hardware stores. I’ve also used other containers such as a 5-gallon bucket or a discarded 5-gallon water jug. It must have a drain hole too.

Concrete Mixing Trays from a Hardware Store Serve as Hydro Herb Beds

5-Gallon Water Container Used As Ebb-and-Flow Module.
(Used a screen at the bottom to retain medium).

Tomatoes Growing Happily in Re-Purposed 5-Gallon Water Jug

At one end of the bed you need a drain hole. However, you don’t want the medium washing out as the nutrient solution drains. You also want the nutrients draining at a proper rate: too slow and the roots would get water logged, too fast through large holes and it won’t fill the bed, and might disturb the root hairs or wash away medium.

In the herb beds in the following photo, I used a c-clamp to control flow back into the nutrient tank. I probably just had a simple screen over the drain hole.

In the large beds I’ve used a simple PVC pipe or tube with holes drilled into it, stuck into a hole in the bottom of the grow bed. I then used silicone or epoxy to seal it in. When water gets to the top of the pipe, it drains fast through the end hole, thus preventing the level from rising any further and over-filling the bed.

PVC Pipe With Drilled Holes Used for Drain

You also need a screen around the drain tube so that medium doesn’t plug up the holes in the tube and to assist in draining.

The holes of the mesh have to be small enough such that the medium doesn’t wash though the holes. Metal window screen, painted with epoxy paint will do the trick. It might need a thicker mesh, such as 1/4″ or larger, to support it. You will want to glue or somehow fasten the mesh circle to the bottom of the bed so that it doesn’t move around. The type of glue you use depends on the composition of the bed. A plastic bed such a concrete mixing tray may requite special plastic glue, as silicone or most epoxies will not stick to it.

Drain Detail – Screen Keeps Drain Tube From Clogging

Be sure to make the top of the drain tube low enough so that the nutrient drains from the top of the tube and recirculates before reaching the top of the medium. You don’t want the plants floating away! (See diagram)

You will want to tilt the bed slightly so that the nutrient solution drains completely. This principal is important: you do not want any standing water. This can lead to fungal growth, root rot, and lack of oxygen.

The growing medium’s function is to support the roots and the plant, hold moisture and nutrients, and allow air circulation. You don’t want a medium that holds too much moisture (for example straight vermiculite) because you will get organisms growing such as fungus, and algae on top, and not enough air exchange. Roots literally breathe, and oxygen and carbon dioxide gas exchange is crucial for healthy and vigorous plant health and growth. Coarse gravel, sand and perlite are examples of mediums that do not hold enough moisture. They dry out too fast and do not retains nutrients for the plants very well. They drain quickly however.

I’ve had great success with white pumice (which just happened to be available at a local nursery). It drains quickly but also holds moisture and nutrients. Expanded clay (sold as “Hydroton”) has similar properties but is lighter weight than pumice (which is good), as does lava rock. These are popular and work well.

Another factor to consider is the weight of the medium and how much your bed can support.

Various materials have been used by growers over the years, including gravel, volcanic rock, sand, perlite, vermiculate, and various kinds of commercially created aggregates (such as Hydroton expanded clay).
I’ve used combinations to get the right kind of weight and moisture retention. For example, a mixture of perlite and vermiculite, or perlite and polymer water crystal beads is very light weight, and good for small beds. The drawback of an extremely light weight medium is that it can’t provide a great deal of support for a large plant, such that a heavy or tall plant could potentially fall over when it gets large.

Hydroponic nutrients is a huge topic. I’ll just give the briefest of outlines and tell you what I used. The essential idea with hydroponics – which literally means water work – is to provide exactly and only what the plant needs in terms of basic elements. Early researchers who were trying to find out what plants actually get from soil – their minimum and essential needs – grew plants in water, and found out by trial and error that all green plants need just a few basic chemical elements from the periodic chart: mainly Nitrogen, Phosphorus, and Potassium. They also need a range of “micronutrients” – metals such as iron and magnesium, in extremely small quantities. They absorb these as dissolved minerals – ions – from the water in the root zone. In nature, these elements come indirectly, from the breakdown of a large array organic materials and rocks, through very complex biological and inorganic processes. Hydroponic methods supply these elements directly, in the form of mineral salts. (Newer methods also use organic solutions – a more complex and difficult technique, needing it’s own chapter).

A salt, when dissolved in water, breaks into the constituent ions. For example, Potassium Nitrate dissolves into Potassium ions (K+) and Nitrate ions (NO3). These are what the root hairs absorb in the water.
Hydroponic nutrients are supplied to the grower in the form of powders or concentrated liquids. Because some of the salts will react with each other and form precipitates (solids) or other combinations that you don’t want, they often come in the form of more than one solution.

The nutrients that I have experience with were from General Hydroponics. I had excellent results. Commercial growers and NASA use them. They were FloraGrow and FloraBloom.

For the ebb and flow systems in the photos, I used a plastic trash can. Any container that is large enough for the estimated capacity, will fit below the level of the growing bed (since it’s gravity fed), and will not react with the nutrients will suffice. Avoid metal containers, as they could potentially react chemically with the salts in the nutrients. You will want something with a cover too – animals or insects and debris can get in your tanks. I once had a hydroponic system on top of a trellis outside my bedroom window in Del Mar, California. The nutrient tank was similar to the bed: a large rectangular tank that fit under the bed. Tree frogs got in it, attracted to the water, and made quite a racket at night!

I used submersible fountain pumps available at hardware stores and nurseries. There are a range of sizes available, rated in Gallons Per Minute (GPM). You want to find one with enough capacity for your system, but not so large that it’s going to create too much flow. You might need an inline valve to control flow. Some of the fittings for tubing and to create a bottom nozzle or drain on a trash can (if needed) were obtained at a Koi pond supply store.

The timer for the pump was an ordinary appliance timer. You can also use a digital timer. Just make sure whatever you use has enough rated wattage to run your pump. I built a box underneath the bed to keep the timers and plugs organized and away from the elements, as you can see in the following photo.

Controller Box Under Big Hydro Bed – Shows Two Timers

The use of a large amount of an aggregate medium means that you will need to clean the medium at the end of a growing season, or at some point, or replace it. This washing is necessary to remove root debris, and possibly precipitates from the nutrients. You may want to also sterilize the medium. How often this needs to be done depends on the condition of the medium and how many plant roots are left behind after harvesting or season’s end.
Another possible drawback is that different plant root systems can get tangled together, making them harder to separate.
Overall though, every technique has it’s drawbacks, so you have to look at what you want to grow and what kind of investment you want to make, what fits your needs and budget, and what appeals to you.

Ebb and Flow hydroponics is a worthwhile technique for those on a budget, and wanting to create a significant growing space for a wide range of crops. It’s a fun way to grow vegetables, herbs and flowers, and is the closest to growing in soil of any of the methods. Using simple materials, an extremely vigorous and fast growing garden can be created – one with few pests (healthy plants have strong immune systems) and no weeds. HAVE FUN!

  • Dr. V. Bhaskar

    April 5, 2012 at 7:10 am | Reply

    I saw the photo of an young radish radicle. Indeed an excellent photo to show the root hairs. But the explanation given about their function is to be verified. Pls go through my new theory/hypothesis published by Science Publishers, Inc., Enfield (NH), USA on “Root hairs – the ‘gills’ of roots (2003). I have shown with ample eviences that root hairs are meant for ‘breathing’ or respiring just like we breathe through nose, and they are the chief points for the entry of gaseous Oxygen molecules. Pls review your understanding of the real function of root hairs and revert with your finding.
    With regards,
    Dr. V.Bhaskar

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