Thoughtful fall clean-up, great garden next
One question that can't wait until you're here:
Can I fertilize a perennial garden in the fall? I used to and then
someone told me it was a bad idea so I stopped. But I think I heard
you say you do fertilize in fall and I think my garden actually
needs it. - N.S. -
A fall application is the single most important fertilization
you can do for a lawn, trees, shrubs or a perennial garden. We hold
off on nitrogen fertilizers between early August and the first fall
frosts so that plants will begin to harden off in response to
natural, late-summer cues of shorter days and lower nitrogen. Then
when fall arrives we augment the soil's natural fertility by adding
organic or slow release granular fertilizer.
Organic materials such as poultry manure, dried cow manure,
compost, greensand, bone meal, feather meal, cottonseed meal and
sewage sludge are like fall leaves. They break down over winter to
dissolve in spring just in time so that their nutrients can be
incorporated into a new season's foliage and stems. The same thing
happens if you use granular fertilizers treated so that they
dissolve only after exposure to certain amounts of warmth and
moisture -- Osmocote and Once are examples.
If we wait to fertilize in spring, we usually wait too long.
Plants resume growth earlier than we expect, during February and
March thaws. As they grow they need nutrients the same way rapidly
growing youngsters need vitamins. So while we're still indoors
longing for spring, trees, shrubs, perennials and lawns have left
winter behind and are taking up fall-applied slow release and
We measure out organic or slow release fertilizer based on soil
test results for a given garden or at a guesstimate rate of one cup
of a balanced fertilizer such as 5-5-5 Organic Blend per ten square
feet of garden. WE spread it after we have cut herbaceous plants
out of the way but before we weed, divide, and plant new perennials
and bulbs. The fertilizer becomes mixed in as we work, and then is
covered with mulch or Nature covers it with a natural mulch of fall
When to expect frost on the vine
When, on average, does the first hard frost occur in my
area - southeast Michigan? - W.S. -
According to the National Weather Service, the average date for
the first killing frost in your area is October 21. It may happen a
few days earlier or later for areas at the edges of developed
"Average" in this case means it's the center of the date
spread. Half the time, that first killing frost comes before
October 21 and half the time it comes later. The earliest killing
frost on record in Detroit in southeast Michigan was September 22,
A killing frost is one that is likely to kill the leaves and
stems of not only tender plants (zinnias, impatiens, eggplant) but
hardier species. The temperature usually falls below 28
For us, gardening continues long after the first killing frost.
Many plants are not affected and still look good, while others are
just coming into bloom. We keep deadheading and removing
distracting brown foliage around those still putting on a show.
During the six or eight weeks after the first killing frost and
before the ground freezes, it's also an excellent time to catch up
on basic gardening and get far ahead of spring work. That's when
we weed, cut, add slow release organic fertilizer, divide,
move, plant, and mulch.
Other gardeners extend their season beyond hard frost by using
cold frames, floating row covers and other strategies to protect
plants. Some are still harvesting tomatoes as well as cool season
vegetables in November when others are bringing holiday decorations
down from the attic.
If your phlox, bee balm or other perennials were
bothered by mildew this year...
...hot compost those fungus-infested stems and leaves to cut
down on the number of spores left to restart the cycle next year.
Then fortify next year's plants against the mildew by dividing them
and replanting only vigorous, outer-edge pieces with just two or
A clump of phlox or bee balm with three stalks will grow
thicker, stronger stems and flowers, will remain open all summer to
fungus-beating air currents, yet look as full or fuller than a
plant with 30 spindly, competing stems.
Green thumbs up
to borrowing your neighbor's garden tool one last time this
year, then giving it back sharpened and oiled!
Green thumbs down
to pruning trees and shrubs in September. Don't prune woody
plants when their leaves are falling or forming. If a shrub or tree
needs cutting, wait until November or clip it during a late winter
thaw before growth resumes.
Originally published 9/18/04