Chapter 3: Hybrids of the Basic Three Methods - Urban Gardening

Urban Gardening

Cool Climate Crops

Chapter 3: Hybrids of the Basic Three Methods

Hybrids of the Shallow Bed on Top of a Wick

Introduction

Ideally I like to be as close to nature as possible. I envision that a seed germinating in a bed of compost, even if it is only an inch deep, "feels" like it is in just the perfect environment to start its life. All of the essential nutrients, water, and air are available to the germinating seed, and it is surrounded by dark soil.

You can get the best of both hydroponic systems (minus the commercial fertilizer) and organic gardening methods by combining elements of both techniques. The photo [insert photo] shows radishes and lettuce growing in a one-inch bed of compost on top of a piece of cloth (the wick). The plants were seeded directly into the compost. The roots adapted easily to the shallow bed. The cloth kept the shallow bed constantly moist as it moved water from the bucket to the farthest corners of the bed.

An old carpet is an ideal wick. Placing a shallow bed on top of an old piece of carpet makes one of our best performing hybrid gardening systems. We discussed the carpet garden in the section on wick gardens. You will recall that the thickness of the carpet allows good and fast distribution of water from the bucket. In this hybrid method, the compost or organic potting mix in which the roots grow makes it less vulnerable to nutrient deficiencies because the nutrients are slowly released as microbial action proceeds. Also the hybrid bed has a greater water-holding capacity.

But there are advantages to having a bed that is itself made up of a wicking column several inches deep made of cloth and some other material. This method can be so light weight that it can be several inches deep and weigh only a few pounds/kilograms when there is no water in the bed.

Our first cola can, old sock garden started out as something like a Mr. Wizard science experiment to help people think creatively about what a plant requires to thrive. It turned out to be a very good gardening method for smaller plants.

I believe you will want to give these innovative methods a try and probably will come up with variations of your own. If you do, send me an email to Martin Price in care of echo@echonet.org.

Hybrids of the Wick in a Shallow Pool-going up instead of out

The cola can, old sock garden.

As I just said, our first cola can, old sock garden started out as an experiment to help people think creatively about what a plant requires to thrive. It turned out to be very successful and useful.

Take any container that has drainage holes about two inches up the sides. I normally use plastic cement-mixing trays that can be purchased at any hardware store in the USA and probably in many other countries. But the container could be any shape and made from anything as long as it has sides and no holes in the bottom, so that you can create a pool containing water and nutrients. For example, an old tire or wooden box with plastic in the bottom would work. The pool forms the reservoir for water and nutrients.

I imagine that most people have old socks that are mismatched or that have holes in them. Soft drink cans fit easily into the socks, one to three cans per sock depending on the size of the sock.

First place an empty flowerpot or other container in the center of the pool. This will be the “monitoring well.” A quick glance into the empty pot will show the water level in the container. It also is a convenient place to quickly add water to the garden. Then cover the bottom with the can-filled socks, fitting them closely together. You will need to have a few socks that hold only one or two cans to fit around the monitoring well.

Give the garden an initial “charge” of fertilizer made for gardens or farms. I do this by sprinkling two tablespoonfuls of fertilizer with micronutrients and one tablespoon of dolomitic limestone across the socks. Then make a second layer of can/socks and add the same nutrients to this layer. If there is room, make a third layer. As discussed regarding earlier methods, you could try watering with manure tea as a supplemental nutrient boost, but I do not recommend relying on manure tea totally.

Add water till the pool is full. I put a tablespoon of hydroponic fertilizer in each gallon of water on the first fill. The first layer of socks soon becomes totally wet as capillary action moves water from the pool. The water then moves on to the next layer of socks etc. The end result is that the roots have abundant spaces filled with air, a constant supply of water, and a constant supply of nutrients. In subsequent waterings you can just add water sometimes and water with dissolved fertilizer at other times, depending on how you perceive the plats are doing.

You can now plant the garden by transplanting flowers or vegetables. Bend the cans as needed to “snuggle” the rootball into the space between the socks. Create as much contact between the rootball and the socks as you can so that water and nutrients are easily transferred into the roots and so roots can quickly start growing through the socks. Cover with a mulch of some sort to keep the sun and wind from drying out the socks. I normally use wood chips, but use whatever is convenient. The photo shows a cement-mixing tray with a bed of can-filled socks planted with six transplanted annual flowers (impatiens). The roots grow in, under and through the socks and around the cans. Sometimes I cut slits in the cans with a penknife so that roots can enter the cans, but I’m not convinced that it makes much of a difference.

If you prefer to start the garden by planting seeds, first form a one-half to one-inch layer of potting soil or compost on top of the socks. Then plant the seeds as you would in any garden.

You could fill the socks with other materials, e.g. pinecones, gravel or even Styrofoam packing material (called “packing peanuts” in the USA). I found that the electrostatic charge that builds up on the Styrofoam makes it difficult to fill the socks. This led me to consider making the garden from layers of cloth instead of socks. The result was an easier and perhaps even better method that I call the “lasagna garden,” so-called after the famous Italian food made from alternating layers of wide noodles with hamburger made from ground beef (plus cheese and tomato sauce of course!).

A “lasagna” garden made of layers of Styrofoam packing material and old clothing

In the United States and I’m sure in many other countries, items that are purchased through the mail often come surrounded inside the box with very light weight packing material made from Styrofoam plastic that is shaped much like a peanut shell. They can become a disposal problem, so recycling them into a great growing medium is very attractive. (I imagine that real peanut shells might work just as well in this method, though they would eventually rot. I have never had enough peanut shells to give real peanut shells a try.)

Begin making the layered garden by selecting some container with no drainage holes in the bottom. Make your own drainage holes two or more inches up the sides. Lay a piece of cloth across the bottom and extending up one or more sides. Cloth made from man-made fibers work much better in the long term because they do not decompose. Microorganisms will attack natural fabrics such as cotton or wool, causing them to rot and disappear within one or two growing seasons. Place roughly an inch of Styrofoam packing “peanuts” on the cloth, then lay the cloth, which you had left extending up the sides, over onto the “peanuts”. It may cover all of the “peanuts” or just part of them. Now place another piece of cloth across the “peanuts” so that they are completely covered. In order to assure that all pieces of cloth are continuously wet, there should be a considerable area of contact between any piece of cloth and one or more of the other pieces. The close contact is important because water being wicked (drawn up) from the pool at the bottom must be transferred from one piece of cloth to another until it reaches the top.

When the container is about a third full, sprinkle some regular fertilizer with micronutrients and some dolomitic limestone (dolomite) on top the cloth. If you have an organic fertilizer that you have confidence in, give that a try instead of chemical fertilizer. Add another inch or so of “peanuts” then sprinkle more of the fertilizer and dolomite. Finish filling to the top, then once again add fertilizer and dolomite.

You may now transplant directly into the bed. Move the pieces of cloth and “peanuts”, cut holes in the cloth, or whatever you need to do to get the rootball into the unusual “planting mix.” Be sure that there is good initial contact between the root ball and the cloth. Add some small pieces of cloth around the rootball if necessary to achieve this close contact. Place a mulch, for example wood chips, grass clippings or rice hulls, on top to keep the sun and wind from drying out the cloth and causing an accumulation of salts near the top (from salts in the irrigation water and from added nutrients).

Water the container well from the top with a solution of hydroponic (i.e. soluble) fertilizer or perhaps a manure tea. Continue until you have added enough that the water starts to drain from the holes on the side of the container. Eventually the less expensive solid garden fertilizer and dolomite will start to release nutrients, but the initial watering with soluble fertilizer ensures that the roots will encounter air, water and nutrients right from the start, wherever they are or grow into.

As the plants continue to grow you can sometimes add water without nutrients. Just remember that when you do it will wash some of the dissolved nutrients toward the bottom of the container. As the roots pull water from the cloth the nutrients will start to move back up as capillary action pulls the water you added back to the top. But if you watered every day, or it rained every day, and the cloth never dried out, the nutrients would not get a chance to cycle back to the top. After a lot of rain, even though the reservoir may be full and the cloth is surely wet, add enough water with soluble nutrients that the roots will be sure to be surrounded with everything that they need for good growth. Ideally the container will alternate from having a full reservoir of water and nutrients to having the reservoir nearly empty.

As was the case with the sock/cola can garden, you can cover the top with perhaps an inch of good soil, compost or commercial potting mix and plant seeds directly into this. This would be the best approach if you would like to use the method but wanted to make it an organic garden.

I have found with both the sock/soda can garden and the Styrofoam packing “peanut” garden that some annual flowers that would typically die during Florida’s hot, humid subtropical rainy season may survive. Sometimes both geraniums and impatiens survived and got the autumn season off to a display of color without the usual wait of a few months for new transplants to grow. I attribute this to having starting with a growing medium that contains no insects or disease organisms and that there is a constant water supply, an enormous amount of air surrounding the roots, and the likelihood that many soil-born disease organisms, should they find their way to the bed, do not thrive in this well-aerated environment.

Hybrids of the Shallow Bed in a Shallow Pool

Results are more reliable the closer you come to making a normal garden. Today our shallow pool gardens are basically hybrids made by placing shallow bed gardens right into the pool of water and extending least two to six inches above the maximum water level.

The roots of most food plants and flowers require plenty of air to thrive. You may have heard that "more houseplants are killed by over watering than by under watering." The problem with over watering is not that the roots do not like to stay moist, but that if heavily watered, water fills most of the spaces ordinarily filled by air in dry soil. So if you filled the shallow pool with heavy clay, it might remain so moist that few plants would grow for lack of air. (We have nothing but sand here in Florida, so have never been able to try a clay soil.)

There is an element of artistry involved in creating the medium in which the plants will grow when the bed is sitting in water. You need to create a medium with such large air spaces that no matter how much water is around, the roots will still find plenty of air, but dense enough that water in the pool can move up by capillary action and keep the medium moist. One way to achieve good aeration where commercial horticultural supplies are available is to include perlite in the growing medium. Perlite is a special inorganic material sold to make potting mixes very airy. Vermiculite, another commercial amendment for potting mixes, does not work as well because it packs closer together, but might be of some use. One formula we frequently use is called the "Cornell mix," so named because it was developed at Cornell University. The Cornell mix contains one-third perlite, one-third peat moss and one-third vermiculite. In many Third World gardening situations perlite is too expensive to consider, but you can come up with alternatives, perhaps rice hulls.

If you have compost or any mix that has a lot of small air spaces, it may work well with most plants. A good way to create air spaces is to incorporate small particles of either organic or inorganic material. We have found that it works well to have a layer of inorganic material that will not decay placed in the pool itself. This might include materials such as sand, small gravel, small pieces of lightweight volcanic rock, or even cola cans with slits cut in the sides to allow roots to get inside. Cover this with small pieces of fresh organic matter (pieces of coconut husk, corn cobs, rice hulls, weeds, wood chips). Finally we place a layer of compost on top. In such a mix, roots will always be able to find air even right at water level.

There is one other step in the above description that will improve performance. We have found that all these large air spaces can be so effective that there may not be enough connections left to pull water by capillary action up to the top of the bed. The result is that the beds must be hand-watered from above until new plants develop roots deep enough to reach the water near the bottom. Including spaces where “columns” of compost or soil extend clear into the base of the pool can solve this problem because capillary action will then move water to the top of the garden via the columns. Newly planted beds should probably still be supplemented with hand watering until seedlings have a good start.

Why do we recommend using inorganic material in the pool itself? In our first version we did use all organic materials. The bed of pole beans did quite well—until the bottom material rotted and the level of the bed dropped. When this happened, many of the roots ended up in standing water. As discussed above, this is harmful or even fatal for the plant. With decay-resistant materials like cans or coconut husk pieces incorporated into the bed, extending well above the water level, the bed can never sink into the pool.

The Wading Pool Garden

An "appropriate technology" shallow pool garden can be made in the USA and I’m sure elsewhere too from the inexpensive plastic wading pools sold for children. I am talking about wadding pools made from a single rigid piece of plastic, not the kind that is inflatable. The drainage holes would quickly destroy the latter! I recognize that this might not be affordable or available in some locations.

Make drainage holes three inches up the sides so the garden can accumulate a significant reservoir of water. Formerly we used a depth of one inch, but less frequent watering is needed with the deeper reservoir. Also tree roots managed to find the lower drainage holes and end up growing in the garden itself. The roots got in as the lawn was mowed and grass accumulated around one or more holes allowing access. At other times ants built a small mound near one of the holes allowing the roots access.

It is important to paint the wading pool for two reasons. (1) It will become brittle after a year or more in the tropical sun. Manufacturers of plastic sometimes include ultra violet light inhibitors to keep the plastic from becoming brittle, but apparently little or none of these inhibitors have been added to the plastic used in wading pools sold in the USA. (2) After a coat of paint (I chose a redwood color) you have an elegant, circular raised bed garden container ready to fill with a growing medium and plant with vegetables, herbs or flowers.

Because most kinds of paint will not stick directly on the plastic, it is necessary to first paint the pool with a “primer.” You only need paint the outside, the lip and down as far inside the pool as the anticipated soil level. The parts the sun does not strike will not be harmed and also will not be visible once the pool is filled. I understand that there is now a paint that will stick directly to the pool. You can inquire about that at your paint store.

Place an empty one-gallon flowerpot on the bottom of the pool, near the center, as a "monitoring well." A quick glance inside the pot will always allows you to see the water level and judge when to add more.

What if wading pools are not for sale or are not affordable where you will be working? A ground-level shallow pool garden could be constructed with a rim of rocks, or even soil, covered with a sheet of plastic. If elevated, wooden boxes lined with plastic can be used. To keep costs to a minimum, the tire gardens constructed to retain a pool of water would seem to be the most durable and inexpensive.

The Eave Trough Garden

Visitors are struck by a variation of the hybrid shallow bed in a shallow pool that we call “an eave trough garden.” It lends itself to an easy method for making a striking wall of flowers. This technique is very appropriate any place where eave troughs are sold. Eave troughs are sold to divert water as it runs off of a roof. They typically come in 10-foot lengths in the United States. I buy plastic rather than metal troughs for their lasting color and because it is easy to cut them. A 10-foot eave trough garden is very difficult to move once it is planted, so I cut them in two to make five-foot troughs.

First the five-foot eave trough must be turned into a shallow pool. You can make a water tight one-half to one-inch barrier” by moving a caulking gun back and forth at first one end and then the other while gently squeezing out caulking to form the “dam.” Caulking guns and tubes of caulking are widely available to fill in around a bathtub or window. Remember to allow a day for it to dry before adding planting medium. If the eave trough is made from aluminum rather than plastic you can alternatively bend the aluminum in such a way as to hold the reservoir of water. But I find that caulking is much easier.

The trough is then filled with planting medium as in the shallow pool garden. Make two “monitoring wells” instead of one by placing an empty 4-inch pot at one-third and two-thirds of the length of the trough. You will use these to add water as well as to note whether the status of the pool at the bottom. To keep the planting medium from washing out at the ends, fill two 4-inch pots and lay them on their sides at each end. Roots will easily grow into the medium in the pots but soil will not wash out.

If you would like to have an extra reserve of water in addition to what the pool at the bottom will hold, place a glass or plastic bottle upside down in the pool with the tops near the bottom. It will slowly release water just like the upside down bucket with a small hole in the lid did in the shallow pool garden.

You can now fill the eave trough with either a good planting medium (commercial potting mix, compost, etc) or use any of the materials discussed in the shallow bed garden section. I have often used wood chips for a lighter weight garden, though it needs to be watered more frequently because the chips themselves don’t hold much water. Sometimes I use wood chips or Perlite in the bottom half to ensure more air deeper in the bed and potting mix in the top half.

This technique is useful only for small plants, unless a trellis and very frequent watering are used. You can transplant or direct seed. For example, I have had good results growing leaf lettuce, onions, radishes and kohlrabi, as well as small annual flowers such as impatiens and begonias and smaller herbs. A long bed of garlic chives (also known as Chinese chives) can produce 12 months of the year for several years.

Here are specific instructions for one way I have made eave trough gardens. (Refer back to the discussion of shallow bed gardens.) After forming the water reservoir, “pool,” and placing the 4-inch pots at the end and 1/3 of the way from each end, fill the trough half way to the top with wood chips. Sprinkle two tablespoonfuls of 10/10/10 fertilizer with micronutrients and 1 tablespoon of dolomite across the chip bed and gently work them into the upper parts of the bed. Fill the eave trough to the top with compost or potting mix. Add the same fertilizer and dolomite amounts unless you know that the potting mix already has good fertility. Now plant seeds as you would in any garden.

If you plan to transplant into the trough, after adding the wood chips and nutrients, place the rootball of the plant so that the top will be near the top of the trough. It is OK if the bottom will be below the high water mark. If the rootball is so small that it will not make contact with water, remove wood chips under it to below the high water mark and fill the hole with your planting medium to help wick water up to the rest of the plant. As an example, I have found it works well to purchase five impatiens (an annual flower) that are available in 4-inch pots. I transplant one at each end, one in the middle between the two “monitoring wells” and the other two in the remaining space. In a few weeks it will be a solid row of color. If I now make an “A-frame” that will hold five of these eave troughs I will have an amazing solid wall of color. If you would rather not go to the work of making an A-frame, you can make a “stair case” of steps using cement blocks for the same effect.

In the Shallow Pool garden, the volume available for air roots seems to be a limiting factor for larger plants. Most larger vegetables only produce well with at least three inches of soil above the water level, although okra is an exception. It seems to be very adaptable to and forgiving of any of these systems, even suspended just above the water in a pile of pine needles! When we finally pulled out the single okra plant in a four square foot shallow pool we found a dense one-inch thick mat of roots.)