When to Add Compost to Your Garden Beds
A healthy garden starts with healthy soil. You don’t need to worry about applying miracle elixirs or wielding new-fangled tools. Adding compost to garden beds is the best — and easiest — thing you can do to produce a bumper crop of vegetables and bountiful bouquets of flowers.
How much compost you need to apply and how often you should apply it varies, depending on the typical soil characteristics and whether you garden year-round.
As a general rule, plan on incorporating compost into your beds before each planting season. When your planting season occurs and how many planting seasons you get each calendar year depends on geography.
Apply compost once per year if you live in cooler climes, such as the Northeast or Midwest United States, Canada, or the United Kingdom, where there’s one major growing season — from late spring to early fall.
Layer partially decomposed compost on empty beds in the fall, before the ground freezes, and let it decompose further through winter. All those lovely nutrients will be ready and waiting for your spring planting.
If you live in the South or Southwest United States, where a warm climate offers year-round gardening, you need to add compost twice per year to accommodate two distinct growing seasons — one cool and one warm — with different annual flowers, vegetables, and herbs planted and thriving in each period.
Because the ground never freezes in warmer climates, soil microbes are working year-round, plowing through organic matter faster than their cool-country cousins. Also, some warm-climate gardeners work with native soils that are naturally low in organic matter.
Here’s a general schedule for applying compost where year-round gardening is possible:
Cool season: The cool growing season extends from approximately mid-September through April, so add compost in late August or early September.
Warm season: Warm-season planting (which overlaps with the ongoing cool-season growth period), starts in mid- to late-February and runs through March, with warm-season plants continuing to grow through summer. Add finished compost before your area’s spring planting season.
Alternatively, if your garden lies empty during intense summer heat, spread compost and let it cover the fallow soil to reduce erosion, combat weeds, and maintain moisture.
If you’re starting a new garden bed, first determine whether the soil is organically rich. This doesn’t have to be an exact science, so you can use a simple “eyeball test” — light-colored soil doesn’t contain as much organic matter as dark brown or black soil. Then follow these guidelines:
Soil with limited organic matter: Where soil isn’t organically rich, add 4 to 6 inches (10 to 15 centimeters) of compost before each planting season.
Soil with plentiful organic matter: If you garden where soil is organically rich, 1 to 3 inches (3 to 7 centimeters) of fresh compost will suffice before each season.
The root systems of most annual flowers and vegetables remain within the top 12 inches (30 centimeters) of soil. Loosening up your soil to that depth helps roots penetrate freely to seek moisture and nutrients. Follow these recommendations for loosening soil and digging in compost:
If you’re lucky to garden where soil is already loose, easy to dig in, and drains readily, you can layer compost on top of the soil and dig it in to a depth of 6 to 12 inches (15 to 30 centimeters) in one step.
If soil is compacted, drainage is poor, or you garden above a layer of hardpan (impenetrable subsoil that restricts water movement and root growth), you’ll grow a more successful garden if you first dig and loosen soil to a depth of 12 inches (30 centimeters). Then layer your compost on top of the soil and turn it under to a depth of 6 to 12 inches (15 to 30 centimeters).