How we weed the lawn depends on which weeds
are there
If the weed is already growing, no use spending the money or
risking the exposure to pre-emergent weedkillers (such as
Trifluralin the active ingredient in Preen; naturally derived corn
gluten meal isn't risky but is expensive). Two examples are
perennial sour sorrel (Rumex acetosella) and"winter weeds"
such as winter-germinating annual weed corn speedwell (Veronica
arvensis). Pull them or dig them from the lawn or bed.
Just a note about timing of spring weedkiller
application:
Sometimes spring comes late or early. Lawn care companies that
operate only by calendar, i.e. "It's April 1, must be spring", may
apply pre-emergent herbicide too early or too late. However, if the
stuff is applied too early it will wash away before it can be
effective, too late and it may be ineffective because the weed
seeds have already germinated. (In addition, early application may
mean people walk on your lawn while it's wet, compacting the soil
and wrecking it!)
Pre-emergent herbicide should be applied based on soil
temperature. Watch the shrubs in your neighborhood and when the
forsythias bloom, the soil is warm enough to warrant crabgrass
preventer.
Unfortunately, there are super weeds...
For those such as star of Bethlehem,
we just keep at 'em.
Below, left: Corn speedwell (orange arrow) blooms with tiny
blue flowers very early in spring. If you want to control it with
pre-emergent chemicals the time to apply them is in
fall. Keep in mind that new grass seed (blue arrow) will
also be killed by pre-emergents, so their use prohibits overseeding
a thin lawn.
Below, right: Many gardeners know sour sorrel (most noticeable
in a lawn in its cold-resisting purple-leaf stage) by its shallow
but extensive, spidery thin and nearly elastic root system with
sprouts from every bit that snaps and remains behind.
We just loosened and overseeded
patchy lawns
Lawns have suffered badly in recent hot, dry years. They're so
thin there is a lot of room for weed seeds of all kinds to sprout,
and where perennial weeds can bulk up.
Early spring is a good time to overseed. Once we coax the lawn
back to thick growth it can crowd out its annual weeds and we'll
know which spots remain where perennial weeds hold sway. We'll dig
them out; an option is to spot-apply a post-emergent broadleaf
weedkiller.
Bulb Star of
Bethlehem a weedy curse
We wrote about a weedy bulb (star of Bethlehem, Ornithogalum
umbellatum) in What's Coming
Up #34.
In the telling of that tale, we touch on almost every aspect of
weeding. We hope you don't have this weed and the closest you ever
come to it is in these photos and excerpt from #34...
