Soil Preparation & Planting in Your Garden

In the foothills our soils are primarily clay, low in nitrogen and phosphorus. Even when planting natives, the addition of compost (homemade, mushroom, composted manure, or some other compost high in microbial activity) is essential to add nutrients as well as air to the clay.

In a vegetable garden, use one part compost to one part native clay soil. If you are cover cropping, remember that the roots of the clover, rye, or other "green manure" add lots of organic matter to the soil, reducing the need for additional compost. If a soil has been covercropped for one season, 4-5 inches of composted turkey manure may be added for each planting season, along with colloidal phosphate (20 pounds per 100 square feet). Most foothill soils are acidic and oyster shell should also be added (5 pounds per 100 square feet).

When planting trees, shrubs, and perennials, most will benefit from a mix of one part compost to 2 parts native clay soil, plus 4 cups colloidal phosphate and one cup oyster shell for a 5-gallon plant (3 times that amount for a 15-gallon, and one-fifth that amount for a one-gallon plant). Even plants preferring acidic soil, when grown in natively acidic soils, will benefit from the addition of oyster shell since this releases the phosphorus necessary for root development and bloom (as well as fruits).Rock garden perennials and alpines typically need a "leaner" soil, one which is amended with compost only to lighten the texture, approximately one part compost to four parts native soil, plus phosphorus and oyster shell in the amounts recommended per 100 square feet.

In Containers

Native clay soil is inappropriate in containers except in very small amounts. In raised beds of 18-24" depth, the mix can be one part native clay soil to one part compost. In other containers, little or no soil is needed. Start with a base mix of 2 parts mushroom compost and one part rice hulls, or a "container mix" from a reputable soil amendment business. Add 4 cups phosphorus (colloidal phosphate or raw rock phosphate) and 1 cup calcium (oyster shell) per 5 gallons of soil mix.

The addition of vermiculite (one 5-pound coffee can full) and perlite (one to two 5-pound coffee cans full) is important. Plants needing higher irrigation or more fertile soils need less perlite, and low irrigation plants need more.

Spread the Roots!

WHETHER A PLANT COMES FROM A 6-PACK OR A 15-GALLON CONTAINER, ROOTS MUST BE SPREAD. If you cannot do it with your hands, lay the plant on its side and use the flat side of a shovel, striking the root ball on all sides. Or a blast of water from a nozzle may loosen roots. Many nursery "soil" mixes have no nutrients. If sand or sawdust have been used as a growing medium, it's alright to reduce or eliminate all of it in the process of spreading the roots.

Mulch!

All plants should be mulched (4 inches deep!) to protect surface roots and reduce moisture loss. Compost, leaves, and straw, or a mix of all of them are ideal mulches. For low-irrigation rock garden and alpine perennials, and subshrubs (Lavandula, Santolina) a gravel mulch is preferred.