If you want healthy, vigorous plants in your garden, you need to get on intimate terms with your garden soil pH.
- Effort: Low 2-3 hrs. (add soil amendments)
- Investment: Low $5-$10 (soil test)
Soil isn’t sexy; for some, it’s dull as dirt. But for a brilliant and bountiful garden, you’ll have to test your soil’s pH. Here’s how you can help your garden soil be the best it can be.
Good soil gives plants energy
Just like people must digest nutrients from food to grow, plants must absorb nutrients from soil to thrive. Soil pH and soil texture influence the types of nutrients that are available for plants to scarf up and use for energy.
What’s with pH?
Soil pH measures its degree of alkalinity or acidity on a scale from 0 to 14. Most vegetables grow best in soil with a neutral pH of 7, which is more of a goal than reality.
Different nutrients are available at different pH levels. Luckily, plants have evolved to thrive in all kinds of soils. So whatever your soil’s pH level, there are plenty of plants that would like to call it home. For instance:
- Azaleas, rhododendrons, and blueberries grow best in acidic soil.
- Hellebores and clematis perennials thrive in slightly alkaline soil.
When you plant a garden, you have two options: Pick plants that thrive in the soil you’ve got (the easy way), or amend your soil to change its pH (more work).
The importance of texture
Soil texture determines how your soil retains water and nutrients. If nutrients leach out of soil, they won’t be around to feed your plants.
Clay and soil rich with organic matter hold water and nutrients better than sandy soils, even though some plants, like cosmos and blanket flowers, prefer a sandy home.
The best soil is a happy combination of sand, clay, silt, and organic matter from leaves or compost. This combo provides plenty of nutrients and encourages healthy root growth.
How to test your garden soil
Garden centers and hardware stores sell DIY soil test kits for $5-$7, which will give you a rough idea of your soil’s pH and nutrient levels. But the most accurate way to test your soil is to send a handful to your county or state soil-testing laboratory, which you can locate through your local extension agent. The report, which typically costs $10, will reveal your soil’s:
- pH
- levels of vital nutrients
- percentage of organic matter
- recommendations for soil amendments
How to transform your soil
Adria Bordas, horticulture extension agent for Fairfax County, Va., says transforming soil is a “very slow process.” Figure a year to 18 months, she says. And the only way to know for sure that your soil has changed is to test it again.
- To make soil less acidic, spread pulverized limestone; or put your fireplace ashes to work and spread them throughout your garden.
- To make soil less alkaline, dig in aluminum sulfate and sulfur, which you can buy at garden centers.
- To make sandy soil less porous, add organic matter (compost, manure, old grass clippings) or humus from the garden center.
- To leaven heavy clay soil, add lots of compost (gotta start that compost pile). Never add a lot of sand, because clay+sand+water = concrete-like soil.
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