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Preparing Soil to Plant Flowers
Good soil isn’t everything, but it’s among the most important things gardeners can control to successfully plant and grow beautiful flowers.
Soil quality, texture, moisture, and nutrients can combine make or break your flower garden.
The ideal soil for growing most flowers is slightly acidic, loose enough to allow root growth, permit good drainage, yet is compact enough to retain moisture. Measured against this ideal, very few homes have perfect soil.
Fortunately, it’s easy to fix most soil problems in your flower beds or borders.
Judging Your Soil
You’ve already learned how to examine your garden’s soil and conduct tests to gauge its nutrients and alkaline-acidity balance, or pH [see: Needs of Flowering Plants].
When it comes to soil texture, it’s easy to dig up a spadeful, reach in, and squeeze it in your hand. If the resulting dirtball slowly crumbles apart when you lightly tap it, your soil’s fine to plant.
More likely, however, it will either hold its shape like modeling clay—it’s too dense—or fall apart and feel gritty—meaning it contains too little organic matter.
In either case, your soil either needs organic material added to it or a specific soil texture amendment, such as garden gypsum.
Acidity and Alkalinity
If you live in an area with soils that evolved from volcanic rocks like granite or basalt over the centuries, or on the site of old evergreen forests, you may face garden soil that is too acidic for most flowers.
Only a pH soil test will tell you for sure, either using a pH meter or a reagent chemical test. Both are available at most garden centers.
Most flowering plants will do fine in soil that is between 6.0 and neutral 7.0 on the pH scale. Unless you’re planting acid-loving species such as astilbe, lupine, or sage, your soil is too acidic (the pH is below 6.0) for many popular flowers.
Neutralize your soil’s acidity with regular applications of garden lime or crushed oyster shells mixed with neutral compost.
On the other hand, if your soil is too alkaline (above 7.0), only plants such as cranesbill, yarrow, or vinca will tolerate the site. You’ll need make regular applications of acidic compost, garden sulfur, or peat moss—a non-sustainable, non-renewable additive most responsible gardeners avoid today.
Repeat applications are necessary because all soils revert to their natural pH balances over time.
For most gardens, amending the soil is relatively easy and will pay off for years to come through easier-to-work beds.
Fertilizer
To promote healthy populations of soil microorganisms, dig in compost or organic fertilizer such as alfalfa pellets sold as rabbit feed, cottonseed meal, earthworm castings, or animal manure.
When working with manures, use less concentrated, high-nitrogen bat or seabird guano than you would low-nitrogen, composted cow or chicken manure. Remember that some steer manures are high in sodium, which increases alkalinity.
Choose organic soil amendments that are aged. Fresh manure contains too much nitrogen for most plants. New sawdust, rice hulls, or ground bark actually rob the soil of nitrogen as they decompose.
Always screen the fertilizer to remove debris and weeds or use weed-free products that are sterilized, milled and sifted to uniform consistency.
Amending Garden Soil
Amending native landscapes’ and garden beds’ soil involves three steps.
First, loosen the soil by turning it over with a shovel or a garden fork—if your garden is large, use a power tiller.
It’s best if the soil is damp to moist, but not soggy. If you quickly hit something that feels like rock, that’s hardpan.
It’s seldom a good idea to mix this dense, sub-surface soil with topsoil. Let it be.
Plan instead to build your beds up with added brown compost and green compost, layered on top of your loosened top soil and mixed in until the worked area is at least 16 in. (40 cm) deep.
If the soil remains loose the depth of a typical shovel or spade—about 12 in. (30 cm), you’ll instead double-dig—turn the soil the depth of two shovels while avoiding mixing the top layer into the bottom one—to prepare the bed for planting.
After loosening the bed’s soil at least 10 inches (25 cm) deep, work in 2–3 inches (5–8 cm) of compost and some organic fertilizer, turning just the top of the soil again.
Rake it smooth and you’re ready to plant. Given such a nice home of prepared, enriched, and amended soil, your flowers are sure to thrive.
Quantity of Amendments
Soil amendments and organic and synthetic fertilizers are available in bulk at landscape material yards and in boxes or bags at garden centers and mass-market retailers.
Most are sold by the cubic foot (0.03 sq.m.) or cubic yard (0.8 cu.m.). Two cubic feet (0.06 cu.m.) covers 6 square feet (0.6 sq.m.) with a 4-inch (10-cm) layer.
One cubic yard (0.8 cu.m.) contains 27 cubic feet (0.8 cu.m.) and covers 80 square feet (7.4 sq.m.) with a 4-inch (10-cm) layer.
Step-By-Step Instructions
Ready soil for planting, add soil amendments, and fertilize by double digging your flower garden beds and borders.
The soil should be moist, neither soggy wet nor powder dry. If necessary, water the soil lightly the evening before you prepare it.
Gather a shovel or tiller, tarp, spading fork, rake, and enough compost, texture amendments, and pH additives to cover the planting area 4-in. (10-cm) deep.
Double digging is easy to understand and perform. Follow the steps shown in these pictures and described in their captions:
How to Prepare and Amend Garden Soil
Begin by clearing all weeds and plants from the soil in the area being prepared.
Remove clay clods, rocks, and debris at least 18 in. (45 cm) deep as you loosen the soil.
Dig a trench 9–12-in. (23–30-cm) deep and one shovel-width wide along an edge of the bed.
Place the soil removed from the trench on a tarp beside the work area.
Loosen the next 9–12 in. (23–30 cm) of soil within the trench with a spading fork or shovel.
Widen the trench a second shovel width.
As you work, place the top 9–12 in. (23–30 cm) of a row’s soil atop the subsoil in the previous trench.
Repeat, working across the area.
When the soil has been double-dug across the area, fill in the last trench with soil from the first row.
Use a tiller to thoroughly loosen and mix the topsoil, removing any debris or rocks and breaking up any remaining clods.
Cover the area with a layer of thoroughly mixed organic fertilizers, compost, and soil texture amendments as thick as required, but at least 4-in. (10-cm) deep.
Always read completely and follow exactly package label directions regarding safety precautions and quantities to apply.
Work the soil amendments into the top 9–12 in. (23–30 cm) of soil using a shovel or fork, mixing it thoroughly with the native soil previously prepared.
Rake the top of the bed smooth.
At first, it will sit high and fluffy with air and amendments; avoid compacting it to retain its texture.
Water the worked area with a sprinkler and allow it to settle for at least 24 hours prior to planting your flowers.