Dear Master Gardener: I have forgotten how to identify poison ivy. How do I identify it and if I have it what is the best way to get rid of it?

Answer: Poison ivy is a plant that is important to identify, so it can be avoided. It can be distinguished from other plants by its leaves, which are always divided into three leaflets. As the old saying goes, “Leaves of three, let it be.” The leaves each consist of three leaflets, which alternate on the stem. Each leaflet is oval-shaped, pointed at the tip and tapered at the base. The middle leaflet has a longer leaf stem than the two side ones. Leaflets may be slightly lobed or coarsely toothed. The leaves' surfaces may be smooth or hairy, glossy or dull, and can vary in color from yellowish-green and green to reddish-green. In the spring young poison ivy plants often start out with reddish leaves. Poison-ivy fruits, which develop in fall, are small white berries with sunken ribs. It is not always easy to identify poison ivy because it looks similar to several common backyard plants including Engelmann Ivy (Virginia creeper) and boxelder.

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Poison ivy is very widespread thanks to the birds and deer that eat the berries and “deposit” them throughout the area in their droppings. The best way to control poison ivy is with an herbicide containing triclopyr, a woody brush-killer. It should be applied directly to the leaves of the poison-ivy, not soaked into the ground. When used according to directions, this herbicide should not injure established grasses, only broad-leafed plants. Apply the herbicide in the spring when the new leaves are fully expanded and the plant is growing actively. Temperatures should be in the 60-to-85-degree range. Avoid windy days when droplets might drift onto the foliage of nearby trees, shrubbery, or garden plants. This is a tough plant to kill, so you may have to spray more than once. Wait two weeks or more between applications, and repeat only if weather permits. Some resprouting might occur several months later. Watch the area for at least a year and repeat the treatment as needed. As with any garden chemical, read and follow label directions carefully each and every time you use it. Be very careful cutting down poison-ivy because all parts of the plant are poisonous; even dead plants are poisonous. Never burn poison ivy as the smoke contains the oil from the plant and can carry toxins causing irritation to the lungs, nasal passages, skin, and eyes. Wear gloves and immediately wash all shoes and clothing that may have come in contact with the poison ivy, since the urushiol oil persists.

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Dear Master Gardener: Should I put a weed-and-feed product on my lawn now?

Answer: It’s a great time to kill certain weeds but not a great time to feed your lawn. Although it is okay to fertilize in May and June the most valuable time to fertilize a lawn is October.

According to the University of Minnesota Extension, the disadvantages to weed-and-feed products include the following:

  • For weed control to be effective, herbicides should be used at specific times during the year depending on which weed species is being targeted. Weeds must be visible and growing at the time of application to be most effective.

  • The time of herbicide application to kill a specific weed may not be the ideal time for fertilizer application.

  • Fertilizer-herbicide products should never be used when the herbicide would be ineffective or unnecessary.

  • For maximum effectiveness and to reduce the chance of damaging the lawn, fertilizers need to be watered in. On the other hand, many herbicides need to remain on the plant leaves for effective weed control. Therefore, weed-and-feed products often compromise the effectiveness of the fertilizer, herbicide or both during application.

  • Fertilizer-herbicide combination products often apply much more herbicide than is needed to kill the target weeds.

Where there are only scattered weeds throughout the yard, it may be best to just spot treat those individual weeds or small areas of weeds rather than applying a weed-and-feed product over the entire lawn. A spot treatment is better for the environment.

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Dear Master Gardener: When do I pinch back my late-blooming perennials to get them bushier?

Answer: Pinching does produce a fuller plant and most tall or thin plants can benefit from pinching. Pinching refers to removing a small amount of growth, usually less than one to two inches from the tip of the shoot. To make tall asters more compact, simply pinch out the tip of each stem to force more side branching every few weeks, starting in late spring or early summer. The newer cultivars of mums do not need to be pinched, but the traditional method is to pinch out the tips on side branches when they have grown six inches and continue pinching until mid-June to the 4th of July, depending on the bloom time of the variety. Pinching the tall growing sedums to four inches may prevent flopping.

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June Gardening Tips

  • As temperatures rise, let your lawn grow taller before mowing it. Taller grass blades help shelter the crowns from heat and wind, protecting them from excessive drying. There is also evidence that roots grow deeper when grass is taller. Mow off no more than one-third of the height at any one time, aiming for a lawn that is 2-1/2 to 3-1/2 inches tall. Allow clippings to fall back into the lawn where they will break down rapidly, recycling nutrients without adding to the thatch layer.

  • Prune spring-flowering shrubs, such as lilacs, forsythia, and early blooming spirea, as soon as possible after blooming to allow next year’s flower buds to form. Older stems can be removed to the ground and plants can be lightly shaped by cutting the longest branches part way back with a pruning shears.

  • Leave the foliage of spring bulbs intact until it turns brown. As long as it is green it nourishes the bulbs for a strong bloom next year.

  • If you move house plants outside during the summer, make sure they start off in a shaded area, then gradually move them into stronger light according to their requirements. Wait until night temperatures are 55-60 degrees.

  • New asparagus and rhubarb plantings should grow unharvested for two full years, allowing roots to grow and establish.

  • Clematis vines take several years to fully fill a trellis. Pinch the central growing point early in June to double the number of shoots.

  • Anthracnose is a fungal disease that shows up almost every year on ash, maple and sometimes oak trees. It causes large dark blotches on leaves, many of which drop. Only rarely is it severe enough to damage trees. Rake up and dispose of fallen leaves. Fungicide is not necessary.

  • Check pine trees for pine sawfly larvae that look like caterpillars. Knock them off with a blast of water from your garden hose.

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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 umnmastergardener@gmail.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.