University of Vermont
Department of Plant and Soil Science
PREVENTING MILDEW OTHER JULY GARDENING
Leonard Perry, UVM Horticulturist
and Charlie Nardozzi, Garden Consultant
Preventing powdery mildew, renovating strawberry beds, and protecting
blueberries from birds, are some of the gardening activities for this month.
At the first sign of powdery mildew on phlox, bee balm, and other
susceptible plants, treat with Serenade or other labeled fungicide, such as
one with potassium bicarbonate (relative of baking soda). Spray plants
every two weeks, or according to label directions if different, thoroughly
wetting the foliage.
Now's the time when strawberry beds can become a mass of baby plants.
Renovate the beds, controlling the runners, encouraging them to root where
you want them. Keep the bed well mulched and watered.
Birds love blueberries as much as we do, so protect the fruit with
netting. Use stakes to suspend the netting over the shrub so
birds won’t reach the berries. Secure the netting to the ground to prevent
birds from sneaking in. Get your cover in place before the berries turn
Take just one-half hour every day to inspect the garden and pull weeds.
Weeds really do sprout overnight and by next week they'll be towering over
your tomatoes and annual flowers. A visit to the garden before work,
or as soon as you get home, can keep the weeds in check.
Continue planting vegetables such as radishes, carrots, and lettuce so that
you'll have a continual supply of these vegetables into the fall. Seeds will
germinate quickly in warm soils, but so will the weeds. Be diligent about
weeding, watering, and thinning your new seedlings.
Check tomato plants for large, green-striped horned caterpillars. A few can
cause lots of damage, so hand pick and destroy them when found. Spray an
organic pesticide containing B.t. (Bacillus thuringiensis) to control
large infestations. If the caterpillars have white elongated eggs on
their backs, leave them and don’t spray. These are a natural enemy,
such as from a parasitic wasp, which hatch and then parasitize other
Protect your squash vines from the squash vine borer. These
clear-winged moths lay their eggs on the stems and the hatching larvae bore
into the vines, causing the plant to wilt and possibly die. Apply a
pesticide containing B.t. every 3 or 4 days during July and early August to
kill hatching larvae before they enter the stems. A thin layer of wood
ashes or moth flakes scattered around plants may discourage egg laying.
If these don’t work on the squash vine borer, slit the vine stem where it is
wilting and along it until you find the feeding grub. Remove and
destroy the grub, then bury the end of the vine so that hopefully it will
root and resume growth.
Summer is a great time to visit perennial nurseries to see what is in bloom,
and add to your collection. There are many local specialists you can
find online under Vermont Perennial Display gardens
(pss.uvm.edu/ppp/vpdgli.html). As virtually all plants you’ll find are
in pots, it is fine to plant them now, just add some compost at planting,
mulch, and keep them watered.
Other gardening activities for this month include visiting open garden days,
removing “sucker” shoots from tomatoes, finishing pruning of woody plants
early in the month so any new growth will have a chance to harden-off before
winter, and replacing hummingbird solution in feeders and water in bird
baths every three to five days.
(Charlie Nardozzi is a nationally known
horticulturist, author, gardening consultant, and garden coach;
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