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The truth about winterizing
your lawn and garden

By by steve strong / area horticulture extension agent
Sept. 10, 2003
The crisp cool snap in the air has 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 instead decide on ways to help your lawn and garden prepare for winter dormancy.
Turf grass, fruit trees and vegetable plants all use up a certain amount of the fertilizer elements that were applied during the growing season. Nitrogen is the first number on most fertilizer blends, and it is the element in charge of greening up and stimulating new vegetation to sprout it is fast acting and also quick to disappear during growing seasons with hot, wet weather.
Nitrogen is not a good choice for winterizing, 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 does (bad idea between Aug. 1 and Christmas), so stop chopping already.
Phosphorus is the second of the three numbers found in most complete fertilizers (like 8-8-8), and is responsible for helping plants to 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 is very slow to break down once it is worked into the soil and may persist for many growing seasons once it is applied.
However, 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. The trick to how good a fertilizer brand performs is the amount of "available phosphate" it contains (or available nitrate nitrogen for the early part of the growing season). That makes it important to read the fine print of active ingredients on the label.
There is nothing wrong with phosphate as a winterizing element, but it may not be needed depending on how many times 13-13-13 or other complete fertilizers have been applied over the years.
One word of caution for those with centipede grass lawns iron is the secret element most often lacking that causes the turf to appear more limey-yellow green colored than other grasses, and too much phosphate actually blocks iron uptake, so avoid the 0-20-20 option on centipede.
Potassium now there is a winterizing element if there ever was one. Potassium is the third and most forgotten number of the big three fertilizer additives, and is the single most important one for winter plant protection.
Potash (0-0-60), as it is also called, 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 leak out of the soil.
Potassium will likely be needed this fall due to the kind of rainy weather we have had for the past year, 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 will tell you they used to spread wood ashes around fruit trees and vegetables long before winterizer fertilizers were invented. The secret to their success was of course, potash, the compound leftover when organic matter like leaves and wood are burned up.
Winterizing with either store bought fertilizers or wood ashes (no more than 25 pounds at a time spread over 1,000 square feet of lawn or garden) can be done at any time, but probably has the best results if applied within six to eight weeks before frost.