Summer!
Slug control now is pointless revenge -- put efforts
into prevention next spring
Dear Janet,
I have trouble with my hostas. The leaves have holes. I
have been told it is slugs or grubs. I have tried everything to no
avail. One year I cut off the leaves but still the
same.
Also I can't get rid of this weed. It's flat to the
ground with tiny oval leaves that each have a dot in their center.
It's not the flat one with the succulent leaves, it's more wiry and
drier than that. It has a woody straight-down root. I've tried
various products but these guys just won't die.
C.G.
Dear C.G.,
Grubs eat roots. Slugs make holes in leaves. Trouble is, most
holes you see now were made months ago as slugs were just starting
their season and growing rapidly. Small holes in young leaves
enlarged with the leaf. Now the slugs are full grown and dormant
much of the time. They're not eating much and when they do, they
have a lush garden to hide in.
That's why spring is the time to deal with slugs. Next April
when hostas are just spears breaking the ground, remove the mulch
from slug-troubled areas. Slug eggs and overwintering slugs are in
that mulch, so hot-compost it to kill them.
Then, while the slugs are breaking dormancy and the plants are
so small that there are no hiding places for slugs in a mulch-free
bed, put out traps. The simplest are sections of newspaper. Wet
them and spread them flat on the ground, intact as if that day's
edition just dropped onto a table ready to read. Put them down in
the morning, flip them over in the evening and you'll find slugs on
the moist underside. Peel off the slug-coated page and throw it
away in a very tightly sealed container. Flip the paper again the
next evening. And the next, for a few weeks or until you stop
finding slugs.
Finally, put clean mulch in the bed and prepare to enjoy a year
with much less damage.
Think about changing the environment to make it less slug
friendly, too. Reduce their food by digging out the worst-chewed
types of hostas and replacing them with slug-resistant 'Sugar and
Cream,' 'Golden Tiara,' 'Blue Cadet', 'Krossa Regal' or any
of the puckered-leaf types such as 'Sum and Substance' or
'Elegans.' Eliminate some hiding places by getting rid of big-chunk
mulches. Make the atmosphere less friendly by letting the bed dry
out between waterings.
You can trap them or put out poison slug baits today but listen
as you do it and you can almost hear them laughing at you from
their myriad hiding and dining places. They are not going to rise
so readily to your bait. Also, holes won't kill a hosta leaf, so
plants don't shed them and grow new ones. So, even if you do catch
or kill a few thousand of the slug descendants of this spring's
hundreds, today's trapping won't fix the problem. You'll still have
the aggravation of looking at Swiss cheese hostas.
Now, about that weed. You're describing prostrate spurge,
Euphorbia supina. It's tough to get hold of, even if it's growing
in the open rather than the paving cracks it excels at filling, and
breaks when pulled. The good news is it's an annual. It isn't going
to survive winter and keep growing a bigger root next year. It
starts over from seed each spring so you have a fresh run at it
each year.
Hoe-ing, pre-emergent herbicide and mulching are all effective,
but no single action provides complete control. That comes with
persistence. In a year like this, when moist times great for seed
germination just won't end, it has been a trial to keep up.
Short report
Yes, those sunflowers are killers!
You're not imagining it. The growing is tough under a bird
feeder amid sunflower hulls and spilled seed. Sunflowers wage
chemical warfare, inhibiting plant growth in their area. Their
tactics are similar to a black walnut's but the chemicals differ.
Agricultural scientists are studying sunflowers and other
allelopathic plants to determine what's affected and how. They aim
to advise farmers on which crop rotations are best and perhaps how
to use sunflowers or derivatives to reduce the growth of weeds like
purslane that are very sensitive to sunflower's presence.
Researchers will sort out which food crops will and won't grow
with sunflowers, but ornamental gardeners must compile their own
lists. On my school's Web site (address below) in the "Ins and Outs
of Plants" folder on the discussion forum, you can read what others
have learned and add what you know. So far the word is that Sedum
Autumn Joy has performed well in sunflower hull mulch for two
years, while ribbon grass (Phalaris arundinacea 'Picta')
survived for over a decade before succumbing.
Green thumbs up
to a temporary truce in the turf weed war. These days it's too
hot for hand pulling and most lawn weeds are toughened and
semi-dormant, resistant to weed killers. Drink some lemonade. Bide
your time. Resume the battle in late September when violets,
chickweed, ground ivy, creeping charlie and weed grasses become
tender and vulnerable.
Green thumbs down
to letting those houseplants take over your home. It's a good
time now to cut them back, root prune, or start cuttings as
replacements.
Originally published 8/7/04