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Compost on established plants

Posted 4/19/2016

With the warm weather that has suddenly arrived, our lovely landscape plants have been producing foliage, flowers, and sometimes fruit enthusiastically, all in abundance. These wonderful signs of spring and summer are possible only because of the nutrition that plants are able to derive from the soil. Diligent desert gardeners are careful to improve levels of fertility, since the soils of the Mojave are notoriously poor.

In nature, the only way plants obtain their essential nutrients is from the soil. Plants that grow in areas where the soil is infertile generally tend to grow slowly, with small leaves and flowers. Gardens, even native style gardens, often include a few faster growing plants, with bigger leaves and flowers. Once we include these into the landscape, true desert soil is not able to provide enough nutrition for the plants to grow successfully.

Containers of fertilizers are available at nurseries or home stores. We do not use the term “plant food,” as plants actually make the food by taking carbon dioxide and water and converting them into sugars. The plants ultimately transform these sugars into everything that they need for growth, such as starches and oils.

It does not matter whether it is organic or conventional, expensive or bargain, soluble or slow-release. If a product claims to be a general-purpose fertilizer, it should contain at least the same three nutrients. These three are nitrogen (critical for leaves, green tissue and proteins), phosphorus (the mineral necessary for roots and reproduction), and potassium (which promotes good water and sugar circulation within the plant).

Conventional fertilizers are fine as sources of a certain number of mineral nutrients. If the gardener also wants to improve the structure of the soil, making it more amenable to root growth, then compost is an important addition. Compost is added when the garden is first installed, but after a few years, it does need to be replenished.

In vegetable gardens, the soil is amended with compost every year, before new crops are planted. Most domestic landscapes only need to be replaced in rare instances, since they are perennial. Perennials are able to continue growing, producing flowers and seeds for years on end. Incorporating compost could be challenging, since working the soil around shrubs and trees could damage tender roots.

Fortunately, the situation is not hopeless for anyone who wishes to incorporate compost into the perennial garden. It is, in fact, surprisingly easy. One needs to have compost, a bucket and a hose attached to a tap. The compost can be from any source.

The method works well, even on rock mulch. Take a couple of handfuls of compost, place them in the bucket full of water, and stir gently enough to suspend the mix. Once it looks like very dilute mud, pour it on the mulch around the plants. When it has drained, take the hose and wash off the mulch. The compost will work its way into the soil, improving it and slowly fertilizing the plants.

This is not “compost tea,” but that will be an article for another day.

Email or call Angela O’Callaghan,Social Horticulture Specialist for University of Nevada Cooperative Extension at 702-257-5581.

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