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MY RANT
November 2009
Archive MY Rant
Fall Fertilizer Follies
The other day I was shopping at a local nursery (for birdseed, not plants) and while wandering around I saw not one, not two, but three signs boldly proclaiming that fall was the ideal time to fertilizer ornamental plants. Really? And on what basis – scientific, botanical, horticultural, or otherwise -- were they making such a claim, I thought to myself?
So let me offer my two cents on the matter: With one notable exception, there is no compelling justification for fertilizing plants in the fall, especially if you routinely fertilize in spring and summer or simply add compost to your soil once or twice a year. The exception would be cool-season turf grasses such as fescue and rye, which convert nutrients from fertilizers into carbohydrates and store them over the winter. But if you use a mulching mower throughout the year and shred the leaves in the fall, even cool-season turf grasses don’t need fertilizer in the fall.
In the case of deciduous plants, including herbaceous and woody types, I would argue that fall fertilization is a complete waste of money. After all, these plants go dormant by late fall, meaning their metabolic rates slow to a near standstill. Why then would they need nutrients, and what would they do with them even if they were available? There is a rapid uptake of nutrients during the weeks preceding dormancy, but that takes place during mid to late summer. By the time fall rolls around, it’s too late for the nutrients in fertilizers to offer any real benefits.
In fact, the practice of fertilizing in the fall can be downright devastating, particularly in the case of evergreens trees and shrubs, and especially broadleaf evergreens such as boxwoods, laurels, magnolias, and azaleas, just to name a few. Fertilizing these babies in the fall can produce new growth, and that new growth is especially vulnerable to freeze damage because it rarely has time to harden off. Ditto roses, by the way.
I did a search using the key words “fall fertilization,” and I got a ton of hits saying that fall fertilization was important. But guess what? The hits directed me to commercial, not scientific websites. In other words, they sent me to fertilizer manufacturers, fertilizer application services, or sites that had banner ads featuring box stores that sell fertilizers. It’s like I’ve always said – The people that tell you plants need lots of fertilizer are the people who make and sell fertilizer. Period.
As is often the case within the world of gardening, people simply regurgitate information they’ve heard someone else suggest or they’ve read somewhere, without taking the time to verify the accuracy of the information. It’s a shameful practice. And it makes me want to puke.
