Ask the Master Gardener: How to take the creep out of creeping Charlie
As shade increases, it becomes more difficult to sustain a lawn and more favorable for weeds like creeping Charlie.
Dear Master Gardener: Some sections of my lawn seem to be mostly creeping Charlie. How do I eradicate it?
Answer: Creeping Charlie is an aggressive, problem weed with one redeeming quality – it attracts and provides food for pollinators. It’s in the mint family and like all plants in that family it spreads by stolons (surface roots) and will regrow from very small pieces left behind in the soil. To discourage it from growing in the first place it is important to have a healthy, vigorous lawn. Proper selection of grass varieties for your site, fertilization, and good watering practices will encourage deeply rooted plants that can out-compete weeds. Most lawns are made up of Kentucky bluegrass and perennial ryegrass and need full sun. As shade increases, it becomes more difficult to sustain a lawn and more favorable for weeds like creeping Charlie.
The key to successful control of broadleaf weeds such as creeping Charlie, dandelions, and plantain is in the timing and proper application of an herbicide. September is the best time of year to control broadleaf weeds in your lawn. If more than 50% of your lawn is creeping Charlie, you may want to consider killing the entire area with a product containing glyphosate and reseeding. Keep in mind you will be killing all plants including lawn grasses. You can usually reseed within a few days after application. If you want to treat a small area, you can use a systemic, selective broadleaf herbicide that contains 2,4-D, Dicamba, or triclopyr. Triclopyr will be the most effective for creeping Charlie. If applied properly, these products will not kill lawn grasses and usually only require two to three applications per year. Read and follow all instructions and guidelines on the label of any product, synthetic or organic, including proper clean up and storage. The herbicide label is the law.
In the past, borax was recommended for eradicating creeping Charlie, but research has shown that adding boron to the soil, even in very small quantities, can create an unfavorable growing environment making it difficult to re-establish lawn grass. In addition, and most importantly, it is an illegal application.
Dear Master Gardener: I have had powdery mildew on my phlox for the last two years and have tried four fungicide treatments and a home remedy I found on the internet. The leaves have continued to die and the plants look terrible. Do I give up, rip all the plants out, and start over next spring? I have many other types of flowers on the west side of the house and they don’t have this issue. Please help.
Answer: Phlox paniculata are very susceptible to powdery mildew. Weather conditions play a role in infection rates and we’ve had the right conditions. Phlox need full sun and very good air circulation to thrive. This can be accomplished by thinning the number of stems in a clump each spring to no more than five, and dividing mature plants every third year. Your other plants don’t have powdery mildew because this fungus is host specific, so the powdery mildew pathogen found on your phlox will not infect your other plants.
According to the University of Minnesota Extension, fungicides are rarely necessary and should only be used to protect high-value plants that cannot be replaced and have a history of severe infection. If you must use fungicides, follow these guidelines:
Fungicides must be applied to healthy green tissue early in the growing season before infection begins.
Examine plants with a history of severe powdery mildew once a week. When the first leaf spot is observed, pinch off the infected leaves and begin fungicide sprays to protect healthy tissues.
Repeat applications are often necessary throughout the growing season and should be applied according to label instructions.
Fungicides will not cure or remove existing powdery mildew infections. Once the majority of leaves have leaf spots, it is too late to treat.
Many different fungicides are effective in protecting plants against powdery mildew if applied correctly. Low impact fungicides like sulfur, potassium bicarbonate and horticultural oils are recommended.
September Gardening Tips
Now is a good time to plant trees and shrubs. Smaller plants are easier to plant and establish more readily. Mulch over the roots with three to four inches of wood chips, keeping the mulch an inch or two from the trunk – it should look like a donut. Water weekly (unless there is enough rainfall) until the ground freezes.
Late summer/early fall is the best time to start a lawn from seed. Spread seed at a half rate in perpendicular directions across the site for uniform distribution of the seed. Lightly rake, allowing about 10-15% of the seed to show. Follow a light and frequent watering regimen by applying light irrigation up to three or four times per day. Minimize irrigation if it rains. After germination, reduce the watering frequency as roots grow into the soil.
Early to mid-September is a good time to apply lawn fertilizer.
Purchase or order spring blooming bulbs to plant later this month. Choose bulbs that are firm with crisp, papery skins and make sure they are hardy to zone 3.
Pick apples when the fruit easily twists off the branch without breaking the spur or branch. Pick plums when they are fully ripe to get the best flavor.
Pick grapes as they reach maturity using taste as your guide. Taste-test a grape every few days and harvest the clusters once they are sweet enough for your liking and have lost their tartness.
Harvest eggplants when they are six to eight inches long and glossy. Use a knife or pruner to cut the fruits off the plant to prevent damaging the plant.
Move citrus plants such as lemon, orange, or kumquat indoors for the winter. Isolate them for several weeks, checking for unwanted insects, to avoid infecting your other houseplants. Grow them in a sunny spot, as they need some direct sun for at least part of the day. Keep the leaves clean by periodically wiping them with a soft, damp cloth.
You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, emailing me at email@example.com and I will answer you in the column if space allows.
University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.