Ask the Master Gardener: Living in the land of 10,000 acorns this year – Brainerd Dispatch

Dear Master Gardener: Help! I’ve never raked and swept up so many acorns in my life! What is going on this year?

Answer: Everyone seems to be talking about this year’s bumper crop of acorns. Oaks make up about 9% of Minnesota’s forests and they are a common tree found in many homeowners’ yards. With so many oak trees around it isn’t surprising that many homeowners have noticed the enormous crop of acorns produced this year. According to My Minnesota Woods, “a single mature oak tree can drop up to 10,000 acorns in a single year. Generally, large acorn crops for oaks occur every two to five years.” It looks like this is one of those years!

Dear Master Gardener: Does poison move from the leaves of a rhubarb plant into the stalk by the fall?

Answer: According to information from the University of Minnesota and Iowa State University, some people mistakenly believe that rhubarb stalks are poisonous in the summer. The stalks grow “woodier” and tougher as they age, but they do not turn poisonous. If your rhubarb plants are healthy, you can pick a few stalks in the summer, without harming the plant, but it is not a good idea to do it very often because it will reduce the yield and quality of your rhubarb crop next year. Plant vigor is the reason you should not harvest rhubarb in the summer. Energy is gathered by the large leaves to be stored for next year’s growth.

The leaves are always poisonous. Although rhubarb leaves contain oxalic acid, which is poisonous, they can be placed in the compost pile. Like other organic acids, oxalic acid is not readily absorbed by plant roots. Compost containing decomposed rhubarb leaves can even be safely applied to the vegetable garden.

  • Fall is a great time to plant trees and shrubs. Smaller, younger plants are easier to plant and establish more readily. Plus, they’re less expensive. Mulch over the roots with 3-4 inches of wood chips, keeping the mulch an inch or two from the trunk — it should look like a donut. No mulch volcanoes please! Water weekly (unless there is enough rainfall) until the ground freezes (which is usually around Thanksgiving or later.)
  • September is the best month to control broadleaf weeds in your lawn. Dandelions, plantain and creeping Charlie are cool season plants that are actively growing in the fall. Dig or pull what you can and spot spray individual weeds or clusters that are scattered throughout the lawn. If you have large patches of weeds you may be better off killing the entire patch using a broad-leaf herbicide containing 2,4-D. Apply it according to the package directions when temperatures are 60-80 degrees. Make sure the grass is actively growing and not drought-stressed. Any chemical or fertilizer can really damage droughty turf.
  • 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.
  • Apply fertilizer to your lawn in early to mid-September. Early fall application encourages increased root growth, earlier green-up next spring, and thicker, healthier grass. 
  • Start lowering the blade on your lawn mower as temperatures cool. Continue mowing until the grass stops growing, generally toward the end of October. By the last time you mow, the height of the grass going into winter should be about 2-2 ½ inches high. Shortening grass height before winter can minimize diseases that occur when grass is too long during the winter. Longer grass over the winter may also encourage vole activity. 
  • Dethatch the lawn every few years in September. Aerate if you didn’t do it in spring.
  • Visit the farmer’s market for a great selection of locally grown, tasty, and nutritious produce. Minnesota grown apples will be ripening now — look for Honeycrisp after Sept. 15.
  • If you grow your own apples, pick them 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 6 to 8 inches long and glossy. Use a knife or pruner to cut the fruits off the plant to prevent damaging the plant.
  • Cure winter squash and pumpkins after harvesting them from your garden by placing them in a warm room for 10 days to toughen their skin. Once cured, you can store them at 50-55 degrees, where they should keep for several months.
  • Although Asian lady beetles are beneficial insects that feed on aphids and other pests, they can be quite a terrible nuisance in the fall. They congregate on the sunny south or west sides of houses as temperatures drop. Some make their way indoors. They are annoying, but essentially harmless. If they get into your home, just vacuum them up and empty them into the trash. Don’t smash them because they will leave stains.
  • Now is a good time to seal cracks and openings with weather stripping or caulk to keep bats out of your house and provide enough time for them to find a new winter hibernation site.
  • Before bringing your houseplants back inside, check for signs of insects, spider mites, eggs or webbing and remove or treat them. Wipe off pots and wash saucers. Remove any plant debris from the soil surface. You may want to re-pot plants with fresh, sterile potting soil to avoid bringing unwanted pests into your home.
  • Plant spring blooming bulbs such as tulips, daffodils, grape hyacinth, snow drops, allium, crocus, and scilla this month through mid-October. Choose bulbs that are firm with crisp, papery skins and make sure they are hardy to zone 3. The sooner you plant your bulbs the more likely they will make it through the winter. Placing a layer of chicken wire over newly planted crocus and tulip bulbs will prevent squirrels from digging them up. To protect your bulbs over the winter, mulch them after the soil freezes. 
  • Move amaryllis indoors before the first frost. Store the bulb in a cool, dark place or continue to grow it in its pot indoors.
  • 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 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.

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