Solutions for landscaping in difficult soil, Horticulture expert tips, Garden earth types

Solutions for Landscaping in Difficult Soil

9 December 2024

Tammy Sons, a horticulture expert, explains that rocky or sandy soil can make it difficult to grow plants. Heavy clay is also difficult to landscape. Here are some tips for dealing with difficult soils in the garden. First, some definitions.

Types of Soil

Picture a triangle with the words silt, clay, and sand along the three sides. The type of soil you have depends on where your garden falls in this triangle. Silty loam is the best soil to have but is relatively rare.

Clay Soil

Clay causes problems because it has few pores or spaces. Water and air compete for the scarce pores, which tend to pool and take a long time to drain. Roots have a hard time growing through clay because the pores are hard to find. Roots also tend to rot in clay soil because water pools in it.

Sandy Soil

Sandy soil is the opposite of clay. The grains of sand have lots of pores. Water drains very rapidly before plants can soak it up. Nutrients leach out of sandy soil, leaving behind a dry, sterile growing medium.

Silty Soil

Silt is between clay and sand in its ability to retain moisture and release it back to plants. It is usually found in bottom lands and can be very fertile if conditioned properly.

Soil pH

pH is the amount of acid or alkaline in soil. The scale starts at 1, for the most acid thing in the world. Seven is neutral, and 14 is the most alkaline thing there is. Most plants, such as blackberries, prefer to grow in neutral or alkaline soil. Other plants, like blueberries, strawberries, and azaleas, like pretty acid soil.

The acidity of the soil affects the availability of nutrients. For example, iron in acidic soils can be difficult for plants to absorb. While you can add lime to acidic soils to reduce their acidity and sulfur to alkaline soils to reduce their alkalinity, it is difficult to make a major change in the pH of the soil. It also takes several years of amending the soil to make a meaningful difference in the pH. You are better off planting things that are adapted to that pH.

Soil Depth

Soil rests on the bedrock below it. The bedrock is a long way below the soil surface in some places. In other areas, barely an inch of soil is over the bedrock. You can tell how deep your soil is by digging a hole. You have plenty of soil if you can dig the hole two feet deep. Don’t fill the hole yet; you will need it to check the soil’s drainage.

Construction Compaction

Many places, especially landscapes around new buildings, suffer from compacted soil. While construction was ongoing, the machinery and traffic compacted the soil, so there is no space for roots to grow or air and water to enter the soil. Water frequently runs off without soaking in. Trees like pin oaks, red oaks, or other large trees that predate the construction often have problems because the soil over their roots becomes compacted. They begin to decline and often fall victim to pests and diseases.

Drainage

If you fill that hole you dug with water until it stops soaking in, you can assess how well your soil drains. Come back in an hour. If the water level has dropped significantly, you have soil that drains well. If the hole is still full, you have poor drainage and must work to amend the soil so it drains well. To improve the drainage, you may need to add topsoil to a low area before landscaping.

Solutions For Difficult Soil

Correct difficult soil to grow a healthy garden. Here are some ways to make your garden thrive.

Add Organic Matter

The best way to treat any soil is to add organic matter. Mixing compost in the top foot of your soil will aerate it so roots, air, and water can pass through. Adding organic matter to sand gives water and nutrients something to stick to, making them more available to your plants. Do not use uncomposted material such as raw manure to amend the soil. The microbes that decompose uncomposted material use some nutrients the plants need, especially the nitrogen plants need to grow. Compost has already been broken down into nutrients plants can absorb.

Till Compacted Soil

If your soil is compacted, till it as deeply as possible. An effective way to do this is a broad fork. You can also use a pitchfork or a shovel to turn over the soil. You will only need to do this once, before planting anything. After planting, avoid stepping in the landscape bed or other landscaped areas. If a path is necessary, use pavers or other permeable material to prevent continued soil compaction.

Fixing Fill Dirt

Fill dirt may have been used to level the property during construction. This dirt is sterile and lifeless. Compost has the microbes this dirt needs to become soil. Mix three inches of compost into the top six inches of soil to jump-start the transformation.

Solutions for landscaping in difficult soil

Differences in Irrigation

Irrigation should be done differently between soil types. Since clay has difficulty absorbing water, irrigation should be on for twenty minutes, then off until that water is absorbed. The best way to do this is to water the soil in one zone for twenty minutes, then cycle through the rest of the zones. Repeat this two to three times so the soil has adequate moisture but isn’t a swamp.

Sandy soil drains rapidly so that you can water it all at once. Too much water will leach the nutrients from sandy soil. Add one inch of water at a time.

Use Native Plants

Many difficult landscapes defeat common ornamental plants. if you use native plants, they are already adapted to the soil type, temperature extremes, and amount of rainfall in the area. The native plants available in your area will differ depending on where you are located and the soil composition of your landscape. However, almost any location has a range of native plants that grow in the area and are suitable for residential landscapes.

Use Raised Beds

One way to defeat difficult soil is to construct a raised bed. Placing a mixture of fifty percent topsoil and fifty percent compost in a raised bed one foot tall creates an ideal environment for most perennial plants to grow. Shrubs will do well in a raised bed, but most trees are too large for a bed that is a reasonable size. You must pick a native tree with care for it to fit in a raised bed. The raised bed must be considerably deeper for a tree than for a perennial.

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