Winterizing your lawn and garden

By By Steve Strong / horticulturist
August 11, 2004
Recent cooler temperatures have gardeners chomping at the bit to perform some kind of outdoor task while the weather is right. Late summer is the time to pack up the pruning shears for a few months, and decide instead on ways to help your lawn and garden prepare for winter dormancy.
Turf grass, fruit trees and vegetable plants all absorb a certain amount of the fertilizer elements that are applied during the growing season. Nitrogen, phosphate, potassium and other nutrients are actually "harvested" when fruit is picked or when grass clippings are sent to the curb and certain nutrients need to be replaced more often than others to maintain optimum plant growth.
The first number
Nitrogen is the first number printed on most fertilizer products (like 13-13-13), and it is the element in charge of greening up and stimulating new vegetation to sprout. Nitrogen can be fast-acting, and also quick to disappear during growing seasons with hot, wet weather. For this reason, slow-release formulas of nitrate fertilizers are often a preferred choice of many gardeners.
Nitrogen is not a good choice for winterizing summer turf or landscape shrubs, since it stimulates new growth, and that is the last thing a plant needs when preparing to hibernate for the winter. Pruning plants also stimulates new growth just like nitrate fertilizer does (a bad idea from September through Christmas), so cut back on the chopping until sometime next year.
The second number
Phosphorus is the second of the three numbers found in most complete fertilizers (like 8-8-8), and is responsible for helping plants flower and make fruit or seed. Phosphate is an energy transfer element at its peak in the middle of the growing season. But, unlike nitrogen, it is very slow to break down once it is worked into the soil, and may persist for many growing seasons once it is applied.
Phosphate is often found in the more popular "winterizer" fertilizers (usually as 0-20-20), indicating the product contains 20 percent phosphate and 20 percent potassium.
How well a fertilizer brand performs depends on the amount of "available phosphate" it contains (the same is true for available nitrate found in nitrogen fertilizers). Read the fine print of active ingredients on the label to determine available levels of nutrients.
There is nothing wrong with phosphate as a winterizing element, but it may not be needed depending on how many times it has been applied over the years in complete fertilizer blends such 13-13-13.
Phosphate overdose actually blocks the uptake of iron in acid-loving plants like centipede grass, azaleas and blueberries, causing the leaves to remain a sickly limey yellow-green color.
The third number
Potassium is the third and most forgotten number of the big three fertilizer additives, and the single most important element for winter plant protection.
Potash as it is also called, sold as 0-0-60, truly acts as "antifreeze" for plant root systems and is a fast-acting element that disappears quickly as frequent rainfall and high temperatures cause it to leach out of the soil.
Potassium may likely be needed this fall due the kind of rainy weather we have had for the past couple of years, but the only way to know for sure is with a soil test. Mississippi State University offers soil testing for just $6 per pint size sample, and the samples can be submitted via check or money order through any county Extension Service office.
Old timers used to spread wood ashes around fruit trees and vegetables long before winterizer fertilizers were invented. The secret ingredient is potash, leftover when organic matter is burned. Winterizing with wood ashes (25 pounds maximum per 1000 square feet of lawn or garden) can be done at any time, but will probably yield the best results if applied six to eight weeks before frost.
Steve Strong is an area horticulturist with Mississippi State University Extension Service.