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Michigan Gardener | May 2013 | www.MichiganGardener.com
ask mg Selecting and growing catmint I would like to grow catmint in zone 6 for a border or even further in the back of the border. Some species of catmint “lay down” and lose their beauty. Are there any species that will stay upright? J.M. There are many varieties of catmint (Nepeta) that can satisfy the border edge as well as act as a backdrop for a border bed. Consider ‘Six Hills Giant’ for the border back. Very hardy and a self-sower, it has violet flowers on 30-inch stems and is frequently used in England to produce that classic sweeping blue haze we see in many magazines. Another erect catmint is Siberian catmint (N. sibirica), particularly the variety ‘Souvenir d’Andre Chaudron.’ It stands staunchly at the back of a bed and requires less frequent dividing than its shorter cousins. Both of these varieties begin flowering mid-summer and go into fall. You can also substitute Russian sage (Perovskia atriplicifolia), which also has aromatic leaves, grey foliage, a myriad of tiny blue flowers, and a strong upright mounding habit to 36 inches. It is often confused with catmint. Butterflies and hummingbirds also frequent this woody perennial. For an upfront border catmint, try ‘Blue Wonder’ which grows up to 15 inches and has dark blue flowers. The popular ‘Walker’s Low’ stays very full and gets about 24 inches tall. The key to keeping any catmint from “melting out” in the middle and laying down is to keep it sheared back as soon as the bloom stalks begin to fade. Cut the bloom stalks down past the last flower. Shearing keeps the woody perennial neatly shaped and stimulates a second round of rich blooms. Remember to stagger the timing of shearing so blooms are available for the many pollinators that love them.
Proper plant spacing In planning for a fuller native garden or border, what is the proper spacing for perennials and shrubs? G.,Detroit The mantra for perennials: first year they sleep, second year they creep, and third year they leap. When intermixing perennials and shrubs, site the shrubs first, paying close attention to their mature width. Purchase from a reputable nursery whose staff is trained to assist and describe how the shrubs behave as they age. Leave enough space between shrubs with only a little overlap. It is easier to move perennials than a five-year-old shrub that begins to crowd its neighbor. Shrubs planted too close will affect the shape and health of each other as they compete for nutrients and light. Site your perennials with the tallest to the back or to the center or focal point. Leave yourself hidden maintenance paths through the middle of the bed so you can deadhead, cultivate and weed as needed. Perennials that are sited well for light and moisture will reward you by expanding to fit the space. It is important to research your selections so you understand their growing habits and their spread. Choosing perennials that clump as opposed to “run” will save you from pulling them out the second year they are in the ground. Select shrubs that are evergreen as well as flowering to maximize your color and interest throughout the growing season. Use simple graph paper and make a planting diagram to help you visualize spacing and position. Plan to review the design every three years so that you can divide and thin more aggressive plants to maintain that “pleasantly full” look.
Siberian squill I have a Siberian squill infestation in my lawn. I’ve tried mowing it down, Roundup, and 2,4-D, but I mostly spent 30 minutes ev-
ery day for months pulling it off at ground level to keep it from seeding and feeding the bulb. Left to its own, it reproduces so thick that it kills areas of the lawn. What can I do to eliminate this plant? T.G., East Lansing This is a classic case of gardening gone awry. Siberian squill (Scilla siberica) was brought to this country as an ornamental and is still sold in many a nursery. It is great for naturalizing. Many gardeners find the electric blue spring flower and grass-like foliage far preferable to crabgrass and dandelions. But it has also escaped into the wild and become invasive. It readily spreads itself with a specialized rooting bulblet and is difficult to get rid of, as broken roots often resprout. It is very hardy and cold tolerant, and is left untouched by critters, from voles to deer. Sadly, the same traits that make it attractive as a garden plant are also what make it invasive. Mowing and pulling off the leaves to starve the bulb would be logical, but not in this case as you have found. It is due to its specialized bulb. Removing the leaves stimulates it to reproduce underground. Since you appear to have some larger patches of squill than others, start with those areas to curtail further spread. Use a full-spectrum herbicide that will be absorbed into the bulb and roots. Yes, this will kill the little remaining grass in those areas. Carefully remove the dead grass, making sure to take the shallow buried bulbs with it. Apply a layer of composted top soil and either re-sod or seed the area.
Vines for privacy I am looking for a vine or climbing shrub the will grow on an arbor/fence, and stay green for privacy all winter in zone 5. My goal is an evergreen privacy fence. I have a freestanding 7-foot tall fence with steel posts, 8 feet on center (the posts are 11 feet long including buried length). There is wire or stainless cable tensioned horizontally between the posts to support the plant. How closely spaced should each horizontal wire be to the wire above or below in order for the plant to climb from one wire up to the next? While the plants are getting established, is it necessary to suspend trellis cloth with a 6-inch square grid against the horizontal cables to help the plants climb? M.T., Franklin Your fence support sounds sufficiently strong to hold the weight of your green privacy screen. The horizontal wires should be approximately 10 inches apart to offer new runners a place to grab on. Provide composted, well-drained soil, consistent moisture through the growing season, and the vines will be quite content. There are three stalwart evergreen vines that are hardy in zone 5. All can handle a variety of soil types and thrive in full sun. First is winter creeper (Euonymus fortunei), which comes in both solid green and variegated cultivars. You often see this vine treated like a shrub, pruned and sheared to a ball, when
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all it wants to do is climb and creep. Its coarse stems grow quickly and new plants will make a noticeable impact in one season. Five-leaf akebia (Akebia quinata) is a hardy vine that readily twines on anything, has nice cinnamon color bark, an interesting 5-finger composite leaf and offers a small purple flower with a light fruity scent. It can grow a foot per day given moist well-drained soil and full sun. Third is English ivy (Hedera helix), frequently used as a groundcover. Often seen travelling up trees and power poles located too near its domain, it twines as well as adheres to itself and anything else with aerial rootlets. Using a combination of these along the length of your fence should provide you with full privacy in a couple years. The trellis cloth may not be necessary with these assertive vines.
Soil for growing grapes What are the soil nutrient needs of Concord grapes. I have heard that they are particular about having the proper nutrients in the soil. S.B., Coleman Michigan has predominantly alkaline soils. Grapes in general prefer a soil pH of 5.0 to 6.0. The range of pH is from 0 to 14, with 7 being neutral. The lower the pH, the more acidic the soil; the higher, the more alkaline the soil. Your first step is to soil test the area where you want to grow grapes. There are over-the-counter soil test kits you can purchase as well as mailorder kits to professional agriculture services. Follow the directions for preparing the soil sample and proceed accordingly with getting it analyzed. The analysis will tell you the soil pH. A professional analysis will also detail necessary amendments to add in what ratio to further lower the pH. Make sure the site for the grape vines is in full sun, that the soil is free of weeds, loamy and enriched with compost, and that consistent moisture is made available during the growing season. Prepare the trellis system according to your preferences. Research the various support systems and make sure pruning and vine training is done during the dormant period. Grapes are susceptible to insects and diseases like any plant. Choosing disease-resistant cultivars is a start. Maintaining sanitary garden practices, weeding regularly, monitoring for insect pests and keeping good air circulation around the plants will reduce their vulnerability to problems. It takes patience to grow grapes of any variety. But if you persevere, you will start to see significant fruit production about the fourth year of growth. Answers provided by Beverly Moss, owner of Garden Rhythms.