The major concerns for any garden are, basically, soil, sun and water. Are they in balance? Are they correct for the plants that you want to grow there? Even if everything seems to be going well right now for a particular garden, will that be true later in the season or next year? Vegetable gardens and flower beds are often located in specific sites as a result of property lines, visual appeal or to be in a convenient location.
That doesn’t always mean that those spots have the best soil conditions or sun exposure to achieve the healthiest, most robust plants. If your garden or bed isn’t flourishing – or if you are about to establish one and aren’t sure if the conditions are right – there are some easy, inexpensive tests that will yield good, quantifiable data that will allow you to make all the work, time and money you spend as a gardener as productive as possible.
Gardens are, of course, not machines: they can’t just be switched on in the spring and expected to run automatically, with occasional weeding and watering, for an indefinite period of time. Knowing the conditions – below and above – the surface is part of the tasks of a successful gardener. But how do you know, really, the conditions? To borrow a phrase from the Michigan State University Extension office, “Don’t guess, test!”
Here are three simple tests that any gardener can – should – perform at least once a year, and sometimes more often than that. They are all easy to do and can provide valuable information that will help you grow the best vegetables and flowers and increase your enjoyment as you garden.
1. Soil Sample Test
It all begins with the soil, but how much do you know about what lies beneath the surface of your garden? The acidity, amount of organic matter, level of important elements and even the ions present in the soil can be easily determined by having a soil test performed by a laboratory.
In the United States, it’s quite simple and relatively inexpensive to have this test done by your state soil laboratory. Each county in every state has an Agricultural Extension Agent, who is a state employee; contact your county agent (they can be found in the “government” section of the telephone directory or online) and ask for a testing kit.
Follow the instructions from the soil kit. They vary slightly from state to state, but in general you use a soil probe, bulb planter or a trowel to dig a small hole 6″ to 8″ deep and collect the soil in a clean bucket or pan. Dig 5 or 6 samples from the area you want tested, restricting the sampling to an area that has similar characteristics (that is, if the soil in one part of the garden is noticeably different, visibly or in the way plants grow, collect just in that area).
Mix the collected soil well and put an amount in the collection bag provided – depending upon the instructions, this will be anywhere from a cup to a pint’s worth. Mail the sample to the laboratory with the fee (it ranges from about $15 to $25, depending on the laboratory). It typically takes two weeks to receive the results.
The report you receive will give you the pH for the soil sample, lime index, the percent of organic material present and the levels of important elements in the soil: phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca). Most reports also include the CEC (cation exchange capacity) number. The CEC measures the amount of positive ions present in the soil, which determines the capacity of the soil to retain nutrients; a value above 10 is considered good.
Usually, the reports do not include nitrogen levels, since these vary widely depending upon recent rainfall and soil type and will change over time. Best of all, the report will include recommendations from the laboratory and the county agent on which fertilizers, mulches, lime and other ingredients will help improve the soil for a better, more productive garden.
2. Sun Exposure Test
All plants need the sun, but the amount of sunlight each tolerates differs from species to species. In general, tomatoes loves lots of sunlight, while carrots yield better roots when they have more shade; zinnia and catmint can take sun all day long, while fuchsia and impatiens prefer less exposure.
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Just looking at where your garden and beds are located will give you some idea of how much sunlight each area receives, but having a more precise measurement can help you select the plants that will do best in a particular place. Generally, “full sun” is defined as receiving 6 to 8 hours of direct sunlight each day, “partial sun/shade” for 3 to 6 hours and “full shade” less than 3 hours.
There are a variety of sun meters available to help you determine the exposure of a particular spot to sunlight. Some use stickers which can be attached to a stake: after a full day, the sticker will change to a color which can be compared to a chart, giving you an indication of how much sunlight reached that area throughout the day.
Of course, these stickers are one-time use only and only provide cumulative information. Electronic meters provide more detailed data; they can be checked throughout the day to let you know when – and how much – sun exposure is received by the location. They can be used over and over, but tend to be more expensive.
Keep in mind that a single one-day reading is just a snapshot of how much sun an area receives. That amount may vary over the spring and summer, as the angle of the sun changes from south to north. Obviously, as nearby trees begin to leaf out, the amount of shade may increase. By the same token, over the years, as nearby trees and bushes grow, the number of hours – and the intensity – of sunlight may change.
That can affect the growth of plants that bloom in the morning (to the plant, “morning” is defined as when the sun begins to reach it) or early- or late-season species. It’s useful to take sunlight readings throughout the year, and over several years, to achieve an accurate picture of the sun and shade for your garden and flower beds.
3. Drainage Test
Most plants require fairly specific conditions for the amount of moisture in the soil. Some have evolved to flourish in damp or even boggy conditions, while others do best in fast-draining soils, but most vegetables and common flowering plants like a happy medium.
The task, now, is to find out how well the soil in your garden or bed actually drains. Fortunately, it’s easy to find out the status of any particular location and, if necessary, take steps to improve – change – the conditions to approach the ideal for the plants you want to grow there.
Dig a hole 12 inches across and 12 inches deep, keeping the sides of the hole straight and the bottom as flat as possible. Use a bucket or hose to fill the hole to the top and leave it for 24 hours. This will saturate the soil, so you will have a baseline from which to measure. The next day, take a straight stick and a measuring tape or yardstick to the hole.
Lay the stick across the hole to give you a reference point from which to measure. Fill the hole with water again and mark the time. Every hour, measure the distance from the stick to the top of the water level and note the measurement. When the hole is empty of water, or at the end of 12 hours, whichever happens first, you will have the data you need.
The ideal rate of drainage for most plants is about 2 inches per hour. Soil that drains less than 1 inch per hour is too wet and more than 4 inches per hour is too fast a drainage rate. With this information, you can improve the soil and/or make other adjustments to the area to give your plants better growing conditions. Loosen wet soil, add loam and mulch and dig drainage trenches to increase the rate at which water drains from an area.
Note that you should not add sand to clay soil to increase the drainage rate: that is actually a recipe for making very durable concrete. For soil that drains too quickly, a bed of mulch will help retain moisture and a drip watering system will keep thirsty plants supplied with water.
Gardens are living, growing, ever-changing systems. Knowing and understanding their basic needs for good soil, proper levels of sunlight and the right amount of water helps to create the conditions that allow any gardener to improve their health and increase the joy that comes from working in them.