This is a good time to fertilize?

Gardeners are asking me if they should fertilize now. The answer is yes, but there are some things to consider before getting started.

In spring, plants put out new growth. The health of that new growth will depend on the plant's health last growing season, whether you fertilized last fall and put compost down to feed the soil, and how much water the plant received through the winter. This past winter was very dry. Without supplemental irrigation, plants, particularly trees, may not be as strong this spring as they have been following wet winters.

If a plant is struggling, it may not be a good idea to put a full-strength inorganic fertilizer on it until its vigor returns. These products can be too "hot" for a stressed plant. Working compost into the soil around the plant would be a better idea. You could also apply an organic fertilizer. Both compost and organic fertilizers tend to release nutrients more slowly and in lesser degrees than inorganic fertilizers, which means they won't burn plant roots.

What are the differences between inorganic and organic fertilizers? Organics are made from animal products or byproducts, such as fish emulsion, manure, and blood or bone meal. They may also be derived from plant products, such as alfalfa tea or cottonseed meal. They contain lower levels of nutrients and break down more slowly than most synthetic fertilizers. Some may only contain one nutrient, rather than containing each of the three macronutrients needed by plants - nitrogen (N), phosphorus (P), and potassium (K). Plants can thrive more when organic fertilizers also contain mycorrhizae, little beneficial microorganisms that build the soil. Inorganic fertilizers do not supply these helpful critters.

Inorganic fertilizers are made from chemicals and usually contain higher levels of nutrients than organically based products. They can work more quickly, particularly in cold spring soils. Often these products are cheaper than their organic counterparts. They work well for greening up lawns in spring. But they can burn roots when used too frequently or in large amounts.

Plants do not prefer organics to inorganics. They just need the nutrients to be available in the soil in an absorbable and usable form. In addition, plants don't care whether a fertilizer is liquid or granular. However, keep in mind that the costs of liquids are much greater per pound for the nutrients supplied.

There are hundreds of products available, many making claims about super-fantastic plant growth. Read the labels. Look for products that supply N, P, K, iron, sulfur, and maybe a few micronutrients. Those that contain mycorrhizae will increase plant performance even more.

• JoAnne Skelly is the Carson City / Storey County Extension Educator for University of Nevada Cooperative Extension.