Today’s informed consumers are growing food at home to ensure that what they are consuming is both free of pesticides and rich in nutrients. These growers are quick to learn there are a lot of confusing so-called best practices for gardening, pest management, and soil amendments. No doubt, some of this confusion centers around over-anxious sales people promoting their products. However, the bulk of the confusion exists simply because every garden, soil, climate, and crop choice has different needs. So while you may readily find reliable information online about the best motor oil for your car engine or the best air pressure for your tires, finding reliable information about the best amendments for your soil will require experimenting on your own.
The good news is, with a basic understanding of soil health principles, some careful observation, and a little trial and error, you can quickly optimize growing the growing practices you use in your farm or garden. If you need and introduction to soil health principles, please consider taking our online course on Building Better Soils.
In this article and a few to follow, I will describe experiments I am running to evaluate biostimulant effects on sugar snap peas grown in container gardens this fall. To get started I needed to make some low-cost container gardens. Here is what I did.
Why Use Container Gardens?
Container gardens are useful for home vegetable gardening for a number of reasons. Gardeners in urban areas may have watering restrictions, space limitations, or neighborhood convenants that limit options for where they can plant. Container gardens can work on a patio or deck.
In some rural areas, like mountain villages with thin soils, or on the arid lands here in the Southwestern US, gardeners simply have poor quality soils to begin with. They may choose to buy pre-mixed gardening soil and plant in container gardens to grow quality produce now, rather than tackle the long term task of soil development.
Gardening in movable containers can provide a level of protection from inclement weather. On cold nights, you can simply move your garden (or your experiment) into the garage.
Container gardens can be a little easier to reach. As people get up in years, it is nice to plant seeds and pull weeds without having to get on our hands and knees. This makes container gardens appealing to many seniors.
For experiments, containers offer a way to control the soil, moisture, and other variables that influence your outcome, so that you can be confident that any differences you observed
can be attributed to the treatment you applied. They also make it easy to replicate treatments. This helps ensure that a random outcome does not get mistaken for a treatment effect.
Since many home vegetable gardeners do use containers, particularly here in the southwest, we have opted to run at least one set of experiments in containers. If you see a need to make container gardens (for experiments or any other reason), read on for a simple “how to.”
Assembling Easy Container Gardens from Plastic Buckets
Container gardens intended for long term use could be built into a landscape and constructed out of materials that blend well with the landscape. In a perfect world, natural, container materials are usually the best choice for gardening. Since my container gardens are for temporary experiments, I want lots of replications, and I want to move these into my garage on cold nights, budget and portability are factors. For this reason, I am using plastic, 5 gallon buckets made of HDPE plastic. A discussion of which plastics are safe for gardening can be found on this unaffiliated garden blog at Epic Gardening.
HDPE plastic containers like the 5 gallon paint buckets shown here will suffice, provided your soil is well aerated, and you have openings to ensure ventilation. The buckets used for this experiment were aerated by punching three ½ inch holes in the bottom of each bucket with a drill, then covering the holes with a 35 cm X 35 cm (about 14 in X 14 in) square of burlap. The burlap allows air to penetrate and lets water drain while holding the soil in place. Next, the bottom 3 inches ( 7 – 8 cm) of each bucket were filled with vermiculite. This porous mineral is commonly added to potting mixes to improve aeration.
If vermiculite is unavailable, perlite, or even pea gravel will work. The goal is to provide a place below the soil where water can easily drain. Finally, fill the bucket with an organic gardening soil, leaving 2 inches (about 5 cm) of empty space near the top. The soil will settle after watering, and this may drop to as much as 4 inches (10 cm) of empty space.
I like to add 1/2 cup of a high quality humate to the soil, like Bloomin Minerals, and blend it throughout the top 12 inches (30 cm). Humates not only improve the cation exchange capacity of the soil, they also adds valuable trace minerals that may be missing. Humates also do a good job of holding on to nutrients that might otherwise wash out the drain holes. In addition, I like to think of humates as prebiotics for soil, because they also support the growth of soil microbial communities. If you buy humates from a garden center, ask your dealer to provide you with an analysis of the trace elements the humates contain, so that you have an idea what minerals you are adding, and what quantities you are adding them in. Keep in mind that dealers are not required to provide exact compositions of individual trace elements associated with natural products, because the cost of analyzing these from batch to batch can be prohibitive. But humates coming from reputable mines will usually have some kind of batch analysis that gives you ballpark knowledge of what trace minerals your humates contain.
Any number of annual vegetables will grow well in 5 gallon buckets. For large plants like tomatoes or cucumbers, a single plant per bucket is adequate, and you should consider a patio variety. For small plants like lettuce, carrots, or spinach, you have room for a few plants, and you may want to experiment with companion planting (combining more than one variety in the bucket).
Plant your seeds or transplants to the appropriate soil depth. Your seed packet will likely have guidelines to follow for both planting depth and spacing between plants. If not, a rule of thumb is to bury the seed to a depth 3X its diameter. For example, if your seed measures ½ inch in diameter, you would want to plant it an inch and a half deep.
In dry climates, going deeper is usually safer than not going deep enough, since seeds that are shallowly planted may dry out or be eaten by insects and birds. I’ve buried seeds to depths more than 10X their diameter, with surprisingly positive results.
For transplants, remove the transplant from its planting container, and gently loosen the root ball. This encourages roots to spread out into your soil. Then bury the transplant to the depth of its original soil line.
An exception to burying depth guidelines can be found with tomatos and certain other transplants which tolerate buried stems very well. In hot weather, you can bury as much as 80% of your tomato plant’s height by simply removing the lower leaves and burying the root ball and stem together. A large transplant could theoretically be buried all the way to the top of your vermiculite layer. New roots would grow out of the buried portion of the stem. This is a good strategy for dry weather, and for dealing with leggy, overgrown transplants.
Mulches help your soil retain moisture and protect your seeds from desiccation. They also seem to deter some pests, like birds, from devouring small seedlings. Un-mulched seedlings are highly visible to birds and small rodents. When small, shallow-rooted seedlings emerge from the ground, a bird can easily pull the entire plant out of the ground.
Seedlings that are hidden under a protective mulch layer have time to develop strong root systems and multiple meristems before revealing themselves to hungry birds. If and when some hungry herbiore nibbles on these more developed seedlings, they may remove leaves, or even parts of the stem, but the seeding will most likely be strong enough to simply replace the missing tissues.
After planting, you will want to cover the top of the soil layer with anywhere from 0.5-4 inches (1 – 10 cm) of a suitable compost or organic mulch. The amount of mulch you use will depend on both the size of seeds or transplants you are growing, and on the kind of mulch or compost you are using.
For green peas (large seeds, sturdy seedlings), and for transplants, a 2 inch (5 cm) depth of loose mulch is adequate, and you can easily use as much as 4 inches (10 cm) of quality mulch. For tiny seeds (like lettuce) you may only need half an inch (1 cm).
If you use woody plant materials like straw or sawdust for mulch, make sure the materials you use have been properly conditioned. Otherwise, when they start to decompose, they will draw nutrients away from your seedlings. For my peas, I chose 2 inches of conditioned straw mulch.
All plants are thought to grow best in association with fungi and other beneficial organisms. A challenge for container gardeners who are using commercial garden soil is that bagged soil stored in warehouses does not provide a beneficial environment for the critters that help your garden thrive. If you have taken my Microbial Analysis for Growers class (this is an advanced course for growers serious about monitoring soil biology), you can look under the microscope and determine whether your soil contains adequate biology, but if you are simply using commercial potting soil out of the bag, you will want to add beneficial organisms.
You can buy commercial mixes of beneficial soil microbes, or packaged organic fertilizers that contain living microbes. You can also grow your own in a bioactive compost or conditioned mulch. Even digging up some earthworms from your lawn and adding them to your containers will help ensure that your containers thrive. David Johnson has an excellent protocol for making compost rich in beneficial fungi. I have shared those in my article about the Johnson-Su Bioreactor.
In upcoming articles, I will discuss some experiments I am running with commercial mixtures that contain live microbes, so if you are not a do-it-yourselfer, stay tuned to see how these might work for you.
Care After Planting-Irrigation and Feeding
Your container garden should be placed in a location with adequate sunlight and reasonable protection from extreme wind, rain, heat, or cold. Some common sense is in order here. You will want to avoid placing your containers on concrete slabs up against the west side of a metal building, where warm afternoon temperatures may exceed 130oF (approximately 54oC), and 60 mile per hour afternoon gusts blow away all your mulch.
You should water containers deeply and thoroughly immediately after planting, using a sprinkler nozzle to ensure that water spreads uniformly across the surface (avoid leaving dry areas) and that your seeds are not uprooted by the force of the water. You have added enough water when you can see water draining out of the bottom of the bucket. For this reason, make sure you have placed your containers in a location where water emerging from under the buckets won’t hurt them. If you need to place them in trays, do so. Both your soil and your mulch should be wet after this first irrigation.
After the first watering, containers should be checked daily for moisture. To check, gently push the mulch aside in a small area of your container, and place your finger in the soil top half inch of soil. If the soil feels dry, water again. Using a sprinkler head, spread about a half gallon of water uniformly across the surface. Be sure to re-spread the mulch that you moved to test the soil.
If you are into gadgets, doubt your ability to detect moisture, or simply want to test your soil moisture without getting your hands in the dirt, you might consider buying a soil moisture meter. Check with your local garden center for recommended models. You may also want to install automatic drip irrigation to ensure your plants get watered even when you are occupied. One word of warning: don’t let automated irrigation take the place of observation and monitoring. Irrigation systems often fail. Sprinklers get clogged, timers get reset, and automated irrigation systems won’t check for pests, so be sure to check your plants often. More on monitoring below.
Once your seeds sprout, the roots will grow quickly, and watering frequency can be reduced. For established plants with roots that extend below the top inch of soil, you will want to wait until the top inch of soil is dry before watering again. When you do water, you should water deep, like you did at planting. Deep watering is particularly important in regions with hard water, since this keeps salts from accumulating in your soil. If you live in a really humid climate, where the top inch simply never dries out, make sure that your soil has good drainage so your plants don’t get waterlogged.
For most situations, household water is of adequate quality for growing vegetables, although chlorine in the water will deter the growth of beneficial soil microbes. Some gardeners opt for purified water. Others may choose to fill a watering can the day before irrigation, and allow the chlorine to evaporate overnight before applying the water to their garden. If you are using a liquid fertilizer, you may mix it with your irrigation water for slow, continuous feeding of your plants. Be sure to consider the recommended guidelines to avoid over- or underfeeding your plants.
As for soil nutrients, the only real way to know for certain that your soil has all the essential nutrients your plants require is to run a soil test, and I don’t recommend this for most container gardeners. Test kits available at garden centers usually test only macronutrients, and while macronutrients may keep your plants growing, they won’t help protect them from pests, and they won’t ensure that the vegetables they produce are meeting your nutritional needs. The problem is, the cost of soil testing for a 5 gallon container garden is rather prohibitive. (A soil test that includes essential macronutrients and micronutrients, pH, and CEC can run as much as $70.00). While the expert gardener can use soil biology and plant properties to make reasonable estimates of soil nutritional status, most beginners and hobby gardeners will benefit from simply choosing a quality organic fertilizer that contains all essential plant nutrients, and applying according to manufacturer’s instructions until your own experience indicates otherwise. Many modern organic fertilizer mixes also contain living microbes that will further enhance plant growth. If you’d like to learn more about soil nutrition, you can sign up for the Building Better Soil online class below.
Check your plants often and make detailed observations about leaf color, pests, and overall growth. Vibrant green color is an obvious plus for most plants, while yellow, white, or brown may be signs of nutritional deficiencies. In plants known for colorful leaves (like ornamental kale, chard, or beets), vibrant colors may also indicate good health. Pests are often indicators of nutritional deficiencies, because a healthy plant is quite capable of pest management.
We will discuss acute pest management options another day, but for now, be aware that regardless of the pest management strategy you choose, you should include an analysis of your overall soil nutrition program. Some organic fertilizers lack trace minerals, and even minerals that are only needed in minute amounts can compromise plant health if they are not present. Other organic fertilizers may lack nutritional balancing. Like cheap vitamins, these fertilizers can promote deficiencies by stimulating excessive growth without providing all the necessary elements to sustain that growth.
Soils that are missing necessary components will not deliver the nutrients your plants need. Just like pharmaceutical drugs have side effects, many pesticides available from garden centers can bind up soil nutrients and compromise plant health, so work on nutritional solutions before you resort to chemical warfare.
Summing it Up
In short, container gardeners offer convenient options for growers who lack the time or space for conventional gardening. They also provide convenient, controlled growing environments for running comparisons of different management techniques. While ornamental and decorative containers are nice, a container as simple as a 5 gallon bucket can produce fresh produce on just about anyone’s budget. The steps outlined above will have you producing vegetables at home in weeks.
In the next article, I will discuss the unexpected results of the tests we are running to evaluate commercial biostimulants alone on pea plants like the ones to the right. Results with each product have been rather unimpressive, but you will never believe what happened when we mixed the two together!