When you should fertilize depends on many factors, especially what type of fertilizer you use, what plants you are fertilizing, and the time of year. In general, you can’t go wrong using a balanced fertilizer in the spring. The following are a few basic recommendations for some plant types.
- Annual flowers and vegetables are heavy feeders. For best results, use a balanced fertilizer in the springtime, and then use fertilizers higher in phosphorous and potassium later in the growing season.
• Perennials and deciduous flowering shrubs benefit from a higher phosphorous and potassium fertilizer after they bloom. Before then, a balanced fertilizer is fine.
• A single early spring application of nitrogen-rich fertilizer is good for most young trees.
• Bulbs enjoy a straight phosphorous fertilizing after the blooms are finished.
There are several different types of fertilizer on the market, and they come in solid or liquid form. Liquids will work faster but must be applied more often; they are most useful for plants that need a quick boost or plants that are losing a battle for nutrients with neighboring plants. Dry (granular) fertilizers, on the other hand, last longer but take effect slower. You can also choose between inorganic and organic fertilizers (for more detail on this subject you can refer to the discussion of this in Module 1: Lesson 2 Soil)
The following tips may be helpful:
• If you use commercial fertilizers, follow the application instructions very carefully. For best results with dry granular fertilizers, use a broadcast or rotary spreader. there are many commercially-available broadcast spreaders, both hand-held and push-type.
• Fertilize individual plants by hand, if convenient. Apply the fertilizer in a ring approximately 5″ from the base of the plant. For larger trees and shrubs, spread fertilizer from the plant base out to the full diameter of the plant or so called “drip line”. After spreading fertilizer, carefully work the nutrients into the soil surface if possible.
• Avoid getting fertilizer directly on plants (except grass!) unless the manufacturer specifically states that you can. Dry fertilizer can burn some plants if it comes in direct contact with the foliage.
• It is best to use dry fertilizers just before it rains. Failing that, watering after application activates the fertilizer and washes it off your plant’s foliage.
• After applying dry organic fertilizers try to work them into the soil rather than leave them on the surface. This helps improve their effectiveness since they can be more readily processed by soil organisms.