As we worked in a client's garden this week, a neighbor popped
over to ask: These violets in the lawn. Is there some kind of
medicine we can use to get rid of them? No matter what we do
they keep coming back!
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Dig or kill
You can dig them out or kill violets
with a weed killer. If you choose to use herbicide, do it early in
the growing season. Use a broad leaf weed killer that lists violets
on its label (at this writing, that's products containing
trichlopyr, or the combination of herbicides called Trimec) or a
non-selective herbicide that does not preclude follow-up planting
or seeding (active ingredient glyphosate as in Roundup products).
Understand that the broad leaf weed killer will probably be only
partially successful and glyphosate will kill both weeds and
grass.
Weak lawn, recurring weeds
However, killing the plants currently
bugging you is not even half the battle. Those violets got in
because the lawn was weak so there were open spaces where seeds
could sprout, yet you've done nothing to improve the lawn's density
and thereby break the weed cycle.
Above: Common blue violet (Viola sororia, a.k.a.
V. papilionacea) is native all over eastern North
America, adapting well to most open areas in sun or shade. Look-
alike marsh blue violet (Viola cucullata) is a lover of
damp places that's also native to eastern North America. These
aren't the only two violet species but these two alone are capable
and ready to occupy any mowed place where lawn grass has open
spaces because of shade, compaction or dampness.
Where turf is thick and tall, most
weeds have a tough time getting started or spreading. So whenever
you address a weedy lawn, determine the environmental condition
that's limiting the turf's growth and correct it. Aerate to loosen
compaction, prune overhanging limbs to increase sunlight or switch
to more shade tolerant grass seed, mow higher so grass blades can
cast the shade that inhibits weed seed germination, then water and
fertilize more regularly.
Timing is key to oust pesty violets
In fall, violets may be most susceptible to broad leaf weed killer
(chemicals that don't kill lawn), although you probably won't see
the results until spring. In spring, you may have more success with
a non-selective herbicide (glyphosate).
Below, left: Most violets form a starch-rich crown, like a
mini-iris. Pull off only the top or leave even a piece of the
crown, and the plant's only diminished, not gone. Better to insert
a fork, loosen the area and then pull. Then the soil has been
aerated as well as weeded.
Above, right: Weeds had no trouble sprouting in the small gaps
between grass plants in this weak lawn. Now there is a big bare
spot created by killing or digging a violet, and the soil there is
loaded with violet seeds. Unless you make this whole area more
agreeable to bluegrass or fescue, and then cover it with grass
seed, your weed killing will only net you a new crop of
violets.
Below: Violets are particularly sneaky weeds. In spring you
probably recognize that they have just bloomed, have seed pods, and
know not to leave the plants lying around to drop those seeds. In
fall, these cunning plants develop "closed flowers" -- blooms that
never open but do produce seeds. See the pods at ground level, and
the developing seed within? Don't leave those laying about,
either!
I hate it when they kill the
violets.
- Virginia Smith -
Weed: What's in a name?
Gardening Law #10: A
weed is simply a plant growing where you don't want it.
Corollary 10A: Even the finest garden plant is a
weed if it puts itself where it's not wanted!
Corollary 10B: If you want it, it's not a
weed!
Right: Well into her 8th decade of
gardening, our mentor Virginia Smith endorsed this,
saying:
"Lower your standards. Don't be such a perfectionist. There
are places where what we cultivate are weeds, and vice versa.
Dandelions are very pretty. I'm not going to worry about that
creeping buttercup. I realized I've been fighting that weed for
something like 50 years and recently I realized it's very
pretty.
I hate it when they kill the violets in my lawn with the stuff
they put on. I love them... the flower, the leaf. They're very
pretty."