If you think that fall is a busy time in your garden you’re right.  There is no shortage of chores that should be completed, and you probably don’t need me to list them out for you.  With all of the tasks at hand, it’s good to know that pruning and fertilizing aren’t on the job list for fall.
As I pointed out in a column last fall, pruning is something best done in the spring and summer, not in fall.  Aside from a tree branch that is nuzzling up to your house’s wall or roof, or long rose canes that sway excessively in the October wind, there is no need to be pruning in fall.
It’s the same with fertilizing, with one exception which I’ll touch on further down the page.  Woody trees and shrubs do not need fertilizer in the fall, as they are in a different mode as the days grow shorter and temperatures drop.
What do you think of as darkness descends outside shortly after the dinner dishes are cleared?  The couch looks pretty good right?  Woody plants, in a similar fashion, are thinking about winter dormancy.  They’re moving starches from their leaves down into their stems and roots before the frost arrives and that transport is cut off.
Because we often have mild weather right through October and into November a shot of fertilizer now may promote a flush of new growth.  There are two negative aspects here.  One is that the plant is busy getting ready for winter and not really interested in putting energy into growth, in the same way that you are getting ready to settle onto the couch and watch hockey all winter while your wife wants to renovate the kitchen before Christmas.
Second, if we do have a solid run of glorious autumn weather and your plants begin to grow after you’ve fertilized them, what happens when a nasty cold front arrives from the Arctic and you wake up one morning (having spent three hours the previous evening renovating the kitchen) to a clear, frosty morning of -15 deg. C?  There will be some damage in the garden to that new growth which hasn’t had a chance to harden off properly.
Houseplants need a similar rest at this time of the year.  Light levels drop off dramatically and growth slows down.  Fertilizing only stresses indoor plants and you’ll likely have weak, straggly stems struggling to reach a light source that really isn’t there.
The exception, and there are always exceptions in the garden, is your lawn.  You’ve no doubt noticed that with the recent rains and cooler temperatures turf is looking pretty good right now.  Your lawn is preparing for winter as well, but it could actually benefit from an application of a fall fertilizer.

Turf grasses will use nitrogen to produce carbohydrates for root growth, not for “green” growth, now.  The potash in fall fertilizer will help individual cells in the grass blades to toughen up for the winter and increases disease resistance.  Apply it now and anytime up until irrigation is unavailable to your lawn.

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