Knowing the soil in your flower beds is important for successful gardening.
Soil is the main source of water and mineral nutrients for plants and must also supply sufficient oxygen to the root system. The preparation of beds for planting shrubs, ground covers, vegetables or flowers is strongly influenced by the initial nature of your soil.
Knowing the characteristics of your soil is necessary for selecting plants that will grow well in it and understanding how you may need to modify the soil for them.
In addition, the soil is full of beneficial microorganisms (bacteria and fungi) that help plants to be healthy. Although you may not realize it, bed preparation is also done to encourage high populations of these organisms, primarily through the addition of organic matter.
Preparation of the bed includes loosening the soil and mixing the aments.
Test your soil
You can learn more about your soil through experience and talking with people who are familiar with the soils in your area. A good place to start is your LSU AgCenter parish extension office, where the extension horticulturist can help you.
You can also have your soil tested by the LSU AgCenter Soil Testing Lab in Baton Rouge. Kits for submitting soil samples for analysis are available from your local extension office and may also be available from nurseries.
The test will tell you the texture (proportions of sand, silt and clay), fertility level for several major plant nutrients, pH and salt levels. The results will help you decide which fertilizer to use and whether or not your soil needs lime.
Never skimp on bed preparation despite the time and effort involved. It is a key technique for successful gardening and is worth every effort put into it.
When planting trees, do not add anything to the soil used to fill in around their roots. Tree roots will spend their lives in the original soil, so it’s best that they get used to the soil as soon as you plant them.
Preparation of the bed
FOR TREES: Trees are usually planted in individual planting holes, not in beds, and you shouldn’t add anything to the soil used to fill in around their roots.
Tree roots will spend their lives growing deep into the native soil beyond the planting hole, so it’s best that the roots get used to the soil where they will grow as soon as you plant them.
The trees you plant must therefore be well adapted to the characteristics of the original soil where they will be planted.
FOR BEDS: Shrubs, ground covers, vegetables, annuals and perennials are planted in well-prepared beds. Since the roots of shrubs, ground covers, vegetables, annuals and perennials will live in the bed, the soil in the beds should be improved with amendments to help the plants grow better.
Here are the basic steps in preparing a bed.
1. Do careful work remove any unwanted vegetation. This may mean reclaiming existing grass to create a new bed or clearing weeds from an existing bed. Weeds or turf can be physically removed or killed with an herbicide (glyphosate is commonly used for this).
2. Flip the ground to a depth of at least eight inches using a shovel, spade or spade fork and break up large clods. You can also use a tiller for this step, but make sure you dig deep enough.
3. Spread any desired soil amendments on the upturned floor. You will almost always want to add 2-4 inches of organic matter. I think homemade compost is best, and every gardener should have a compost pile. If you can’t make your own, you can also buy bagged composted organic material from nurseries and garden centers.
Other suitable choices of organic matter include aged manure (available at local stables or bagged at nurseries), alfalfa meal, and agricultural by-products, such as cotton gin waste, bagasse, or mushroom compost.
Or, if your soil is particularly heavy, finely ground composted pine bark is excellent for improving drainage and loosening the soil (generous amounts of sand can also be added to heavy clay soil to improve it).
I cannot stress enough the benefits of adding organic matter. Remember that it also encourages high populations of microorganisms that help plants grow better.
4. If necessary, soil pH can be made more acidic with the addition of sulfur or more alkaline with the addition of lime to better suit the plants you intend to grow. But remember, it is better to choose plants adapted to the natural pH of the soil.
5. You can also add fertilizer on the floor when preparing the bed. Choose a fertilizer that provides nutrients that a soil test has determined are low.
A general purpose fertilizer is usually appropriate (the analysis should have a higher first number, a lower middle number, and a third number in between, such as 15-5-10). Appropriate organic fertilizers or commercial fertilizers could be used.
Be moderate when applying fertilizer. Excessive fertilizer applications can lead to nutrient runoff into sewers and possibly pollution of surface water bodies like lakes and streams.
6. Finally, mix well any amendments you have applied in the floor of the bed. Make sure amendments are fully incorporated into the top 8 to 10 inches of soil.
A tiller is ideal for this step, but it can also be done by hand if the soil is not too heavy. Smoothly rake the bed and shape the sides and you’re ready to plant.
When you’re done, you’ll find that the bed is several inches higher than it was before preparation. This is desirable as it will help improve drainage.
If you decide that the soil you are dealing with is simply too poor to garden in (as sometimes seen in new construction where the site was filled with subsoil), you may decide to ditch the soil and bring mixed topsoil or garden soil to make your beds. Build the bed with the soil mixture about 12 inches deep above the existing ground.
October is the perfect time to plant cool season vegetables in your garden. They include beets, broccoli, Brussels sprouts, cabbage, carrots, cabbage…
Garden columnist Dan Gill answers questions from readers each week. To submit a question, email Gill at gnogardening@agcenter.lsu.edu.
