Autumn feeding for lawns

Garden Making

Passing through a garden centre, you might notice the stacked bags of autumn lawn fertilizer. If your lawn has been on a low-nutrient diet (that is, you’ve just not bothered to feed it this year), now is the time to make up for sins of omission.

Mid-autumn is the most crucial feeding time for a lawn, and if you fertilize only once a year, autumn is the time to do it. Autumn fertilizers vary widely in their nutrient formulas, and include amounts like 12-3-18, or 4-8-12. My own guideline is for the nitrogen content (the first number in the formula) to be below 20, so either of those ratios would be acceptable. Nutrients applied between late September and late October are absorbed into the plant crowns, stored and released in spring, as needed. This allows the lawn to make its own decision about when to begin growth, drawing on banked nutrients, first for root growth, followed by blade growth. Fertilizing in autumn, when soil and air temperatures are declining, won’t stimulate blade growth this season, but will ensure a vigorous and healthy start for the lawn next year.

I always purchase extra bags of the autumn formula so that I can have some on hand for an early summer feeding next year. I don’t use high-nitrogen fertilizers (sold in spring and summer) on the lawn because it puts too much stress on grass plants to produce blade growth at a rapid rate. Such fast growth can result in excessive moisture requirements, and possible buildup of thatch. The lawn needs food, but not an explosive diet. I realize there’s a difference of opinion on how much nitrogen to give a lawn, and I err on the side of caution. I’m already feeling twitchy about causing controversy, so I’ll leave the excessive nitrogen issue alone for now. But I could go on.

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