Ask the Master Gardener: Girdling roots can be harmful to trees
Girdling roots are roots that grow in a circular or spiral pattern around the trunk of a tree at or just below the soil line. They cause the tree to suffer a slow decline in health and gradually strangle the trunk.
Dear Master Gardener: We moved into a house and noticed the roots of several trees are girdled. Why did this happen?
Answer: Girdling roots are roots that grow in a circular or spiral pattern around the trunk of a tree at or just below the soil line. They cause the tree to suffer a slow decline in health and gradually strangle the trunk. As roots circle the trunk, they can slow and eventually cut off the flow of sap in the tree so water and nutrients cannot get to the leaves. This is typically due to improper planting techniques, such as the following:
The tree was planted too deeply. This is the most common mistake. When root systems are buried, less oxygen and water is available. The roots will grow up towards the surface of the soil and tend to encircle the trunk. The more deeply buried the roots are, the fewer the roots available for the tree to become established. Trees and shrubs need to be planted so their first major roots sit just below the soil surface. When planting them it is important to carefully remove some of the soil from the top of the container or root ball, to determine where those first roots are located.
The tree or shrub was root-bound in the container and it was planted that way. The tighter the root ball, the more the root system should be untangled. Loosen and straighten circling roots. Cut off rotten, misshapen, or damaged roots.
Mulch was piled too deeply around the trunk creating a “mulch volcano”. Make a doughnut instead. Keep mulch three to four inches from the trunk or stems. Beyond this area of bare soil, place a three- to six-inch-deep layer of organic mulch, such as wood chips, out to the edge of the tree or shrub canopy.
Planting the tree in a hole that is too small so the roots cannot easily spread out. The hole should be at least 1 to 2 feet wider, but not deeper, than the splayed-out root system. A larger hole will allow for better root growth, especially in poor soil.
Answer: Chances are they were not brown recluse spiders. There are two types of spiders in the United States that are notorious for their venomous bites to people — the brown recluse and the black widow — neither of which are native to our area. It is extremely rare to find brown recluse spiders in the Upper Midwest. Only one specimen has been recorded in Minnesota and that was in Lake County in 1953. Two specimens have been recorded in Wisconsin in the last 25 years; and there have been several reported specimens in southern Iowa. Confirmed bites from these spiders are very rare in the Upper Midwest.
The brown recluse spider is tan to dark brown, nearly one-half inch in body size, and has a distinctive dark violin-shaped marking on top of the front body section. It has six eyes instead of the usual eight.
July Gardening Tips
Stop harvesting rhubarb and asparagus now to ensure productivity next year.
Fertilize tomatoes with a balanced liquid fertilizer when they start blooming.
Water evergreens well during hot, dry weather.
Leaf lettuce, spinach and radish turn bitter and bolt in July’s heat. Pull them out of the garden and replace them with broccoli, cabbage, or cauliflower for fall harvest.
Stake tall floppy plants such as dahlias, balloon flowers, delphinium, and monkshood.
Pick vegetables when they are at their optimal size and maturity for best eating. Green beans, cucumbers, and summer squash taste best before they get too large.
Children (and adults) may enjoy creating a “watering hole” for birds, bees, and butterflies by setting a deep saucer or pan on top of an overturned pot. Add a rock as a landing pad.
Now is a good time to shape hedges. After the second flush of growth, hedges and shaped shrubs should be pruned.
Remove faded blooms from flowering perennials and annuals. Deadheading promotes continued blooming by preventing plants from setting mature seeds.
Whether picking your own flowers or buying them from a farmers’ market, take off the lower leaves, then cut the base of the stems at a 45-degree angle before putting them into a vase of water. Change the water every day or two. Better yet, dissolve floral preservative in the water before adding the flowers.
Thin apples when the fruit is about marble size (early July). Thinning fruit off the trees by hand will promote larger, higher quality fruit. Leave one or two fruit per flower cluster or about 4 to 6 inches between fruit on any branch.
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 firstname.lastname@example.org 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.