Dear Master Gardener: Last year in late spring/early summer there were caterpillars on my Colorado blue spruce tree that caused extensive defoliation. What should I do this year to protect the tree?
Let me first start out by saying that the Colorado blue spruce is not native to Minnesota, and those planted here rarely live beyond the age of 30. They are more prone to infection than our native white or Norway spruce.
Perennials such as the butterfly weed make a good addition to a butterfly garden.
Regarding the caterpillar problem, the most likely culprit is either the spruce budworm or the yellow-headed spruce sawfly. The larvae of the spruce budworm are olive brown or reddish brown caterpillars that get approximately 1-1/2 inches in length at maturity. They become active in mid to late May and can extensively defoliate trees.
The yellow-headed spruce sawfly tends to attack isolated spruce, like those found in landscapes. The larvae have yellow or reddish brown heads and olive-green bodies with six gray-green stripes. They appear and begin feeding in late May to mid-June and feed for about 4-6 weeks. Three to four consecutive years of defoliations can kill a tree.
To try to eradicate the damage-causing insects, spray foliage when larvae are less than or equal to their full-grown size and before damage is extensive. Bacillus thuringiensis can be used for spruce budworms but is not effective on sawflies. Insecticides that are effective for either are acephate, azadirachtin, bifenthrin, fluvalinate, insecticidal soap, malathion, permethrin, pyrethrins and spinosad.
It is essential to read the label before you buy a pesticide to be sure it is registered for the pest you wish to treat. Read the entire label and observe all safety precautions on the label.
Perennials such as the "Autumn Joy" sedum make a good addition to a butterfly garden, according to Crow Wing County Master Gardeners, who are trained and certified volunteers for the University of Minnesota Extension Service.
Dear Master Gardener: I start my tomatoes from seed under fluorescent lights but they seem to be spindly in comparison to the tomato plants you buy at a nursery. Does it have something to do with the amount of light they get?
Fluorescent lights are the best way to start seeds. Keep the lights about two inches above the tops of your seedlings and no more than four. Lack of light is the major cause of spindly stems. Plants need 12-16 hours of light daily. Do not leave the lights on continuously because many plants need a dark period each night to develop properly.
Also, provide a constant heat source underneath your seedlings as seeds of most plants started indoors germinate sooner and produce healthier roots when the potting mix is warm. Electric heating mats for seed starting may be purchased via many garden centers and mail-order suppliers.
Dear Master Gardener: I am going to plant blueberry bushes in large whiskey barrels to try to control the pH level of the soil, as I know blueberries need a low pH soil. Do I need to do anything different with them in large containers as opposed to being in the ground and will I need to protect them next winter?br>
Growing blueberries can be challenging because the plants need acidic, well-aerated soils with a high water-holding capacity. Whether you grow them in containers or in the ground, the soil can be amended to make them suitable. You should be able to amend the soil for your blueberries just as well in the ground as you can in a container.
You may want to get your soil tested by sending a sample to the University of Minnesota so as you know what you need to do to get the 4.0-5.0 pH needed to successfully gow blueberries. Peat may be added to acidify the soil and increase the organic matter content.
Different sulfur compounds also may be used; iron sulfate reacts faster than elemental sulfur but is more expensive. Aluminum sulfate is not recommended because it can be toxic to roots at high levels.
Blueberries do best in a sunny location. Water the plants often enough to keep the soil moist - but not saturated - throughout the life of the plants. Mulching the plants also helps to maintain uniform soil moisture and to reduce soil temperature in the summer.
In regard to over-wintering blueberry bushes in containers, plants grown above ground in a container (even those hardy to our zone 3) do not tolerate having their root systems frozen. If you are going to keep them over the winter in containers, you may want to consider moving them into an unheated garage.
Dear Master Gardener: I would like to start a garden to attract butterflies but don't know what to plant. What do you suggest?
Butterfly gardens are justifiably popular, providing color and motion. Annuals are perhaps best because they provide the longest-lasting color. In that category, nasturtiums, marigolds, petunias, heliotrope and dill would qualify. Good perennials would be purple coneflower, hollyhock, Joe Pye weed, butterfly weed, "Autumn Joy" sedum, mallow, liatris and honeysuckle. Plant perennials that have varied bloom times to provide consistent bloom.
Some butterflies feed on a single species of plant, such as the monarch, which feeds only on milkweed. Avoid double flowers because many of them are bred for showiness, not nectar production. Provide a mud puddle or a shallow dish of water and remember to feed the caterpillar stage as well. You will want to learn to identify which caterpillars turn into which butterflies so that you don't destroy them.
Dear Master Gardener: How do you get rid of dandelions?
Dandelions are perennial weeds with long top roots and are so ubiquitous that their seeds are everywhere and can persist in the soil for years. Any thought of getting rid of them once and for all is not reasonable.
Spring is a good time to start the ridding process. If your lawn is only lightly infested and in only a few spots, remove them by hand with a dandelion digger (a long, narrow, metal tool with a notched end) or a handheld can of weed spray labeled for dandelion removal. You also could carry a bag or can with you as you do this, plucking off any flower heads and buds and destroying them before they spread their myriad seeds for another crop. This avoids spraying the whole lawn with unnecessary herbicide.
If, however, you have too many dandelions for hand treatment, find a lawn herbicide labeled for killing dandelions and spray or drop-spread the whole lawn. Often, such products are combined with lawn fertilizer (the so-called "weed and feed" products). They are most effective when applied on a calm day with temperatures in the 60s and 70s and no rain forecast for 24-48 hours.
Fall is the ideal time for dandelion removal and you may need additional treatment then. Hand removal in future years will probably keep the dandelion crop in check, as will a thick, healthy lawn.
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.
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