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August tips: From planting grass to eliminating creeping Charlie

Barbara Gmitro-Best took this photo of a bee at work in her East Gull Lake yard.

• For best flavor and texture, pick and use zucchini, cucumbers and snap beans when they are young.  Check your garden daily for optimal size.

  The best time to plant grass seed is mid-August through mid-September.  Scratch the surface to be planted with a rake to ensure good seed-to-soil contact.  Use starter fertilizer and water regularly but lightly until the grass is established.  Do not use weed killers until next year when the new grass has had time to toughen up.

• Divide and replant overgrown perennials, especially iris.  Discard old, woody growth and replant the outer portions. These new clumps will now have time to reestablish before freeze-up.  Cover with mulch before the ground freezes for extra protection.

• Blossom end rot on tomatoes shows up this month.  It consists of black, leathery sunken spots on the bottoms of the tomatoes. It is caused by lack of calcium and inconsistent watering.  To avoid it, water tomatoes regularly and deeply.

• Fertilize roses one last time in early August.  Although roses are heavy feeders, fertilizing after then prompts new growth when a plant needs to slow down to harden off for winter.  Pruning now would also promote new growth, so save your pruning for spring.

• Impatiens blossoms attract hummingbirds—and also sphinx moths, which resemble hummingbirds in size, shape and hovering habit.  Look for them in the early evening.

Dear Master Gardener:

The red-twig dogwoods I planted in my yard last year have been eaten, I am assuming, by deer. Will they live and is there something I can do?

 There have been reports by readers in the area that their dogwoods have been defoliated. This problem is due to voracious sawfly larvae, which resemble caterpillars. The most likely culprit is the dogwood sawfly larva, which feeds on the leaves of various dogwoods, particularly redosier and gray. The larvae change color pattern as they develop and when fully grown are cream color with prominent, mottled black spots. Young larvae skeletonize leaves in early summer until the leaves are completely consumed and only the mid-veins are left.

 According to the University of Minnesota entomology department, chemical control of the sawfly larvae is only effective when the larvae are less than 25mm long because after that point they stop eating the leaves and build cocoons. Biorational pesticides, such as azadirachtin, horticultural oil, insecticidal soap, pyrethrins, and spinosad are effective against sawfly larvae. Conventional pesticides, such as, bifenthrin, malathion, and permethrin are also effective. Most likely, your dogwoods will survive the attack.

Dear Master Gardener:

Mushrooms are randomly appearing in my lawn.  Should I be concerned?

 With all the rain we have been receiving, it is quite common to find mushrooms appearing in lawns and gardens. These fungi help the beneficial process of decomposing soil organic matter and are not an indication that there is a lawn problem. If they bother you, just rake them up and dispose of them. Please remember that these mushrooms are not edible!

 If dark green circles or arcs appear in your lawn, this is a fungus that causes a problem known as fairy ring.  If you see this, consult the turf grass disease section of the University of Minnesota Extension’s gardening information page on the internet at: for more information.

Dear Master Gardener:

My lawn is being overtaken by creeping Charlie.  How can I get rid of it?

 Creeping Charlie is botanically known as Glechoma hederacea but is also commonly called ground ivy or creeping jenny.  Its leaves resemble tiny geranium leaves and its stems creep along the soil surface up to 30 inches in length, sending down rootlets at each node.  This growth habit makes it difficult to eradicate.  In the spring pretty and abundant tiny blue or purple flowers appear.

 You have several options in dealing with it.  The easiest is to learn to love and appreciate it as a ground cover. It is hardy, thick, always green and requires little or no mowing.  Another way is to remove it by hand (especially effective in the spring) or with a dethatching rake, a heavy and laborious task.  Finally, you can remove it chemically with herbicides containing 2,4-D and MCPP as their active ingredients.  These herbicides will damage or kill any broad-leafed vegetation with which they come in contact, so use them with caution, following label directions carefully.  The best time to spray is in the fall when no rain is forecast for 48 hours. Repeat applications may be needed every 10-14 days.  For a time a borax application was recommended to eradicate creeping Charlie, but it was discovered to be too toxic and soil-persistent and is no longer a University recommendation.

 If your lawn has more creeping Charlie than grass, you may want to start over.  To do that you will need to strip the sod with a sod cutter or apply glyphosate (Roundup) to kill the entire area.  Then you can redo your lawn by preparing your soil and seeding or sodding.

Crow Wing County Master Gardeners are trained and certified volunteers for the University of Minnesota Extension Service.  All information given in this column is based on research and information provided by the University.  To ask a question, call the Master Gardener Help Line at 218-824-1000, extension 4040 and leave a recorded message.  A Master Gardener will return your call.