During last season, my hosta leaves were really chewed up. Is this due to mites or slugs? Any recommendations on preventing it?

Mites are not what chewed your hosta leaves. It’s those slimy critters that are part of the mollusk family: slugs. They, as well as garden snails, use tooth-like jaws to saw through leaves and flowers. Like bats, these garden pests feed at night and on overcast or rainy days. They are most active during warm, rainy springs. While there are more than 25 slug species in the United States, hostas’ real enemies are the little black and brown slugs that eat both shoots and roots.

Slugs slide along on a slime trail that’s excreted by their single large foot. Their eyes are located at the end of the large tentacles on their head, while the smaller tentacles enable them to smell. Slugs are hermaphroditic, containing both female and male organs. Nonetheless, they need to pair in order to breed, usually in the spring or fall when weather is mild and moist. In fact, slugs are more prolific than rabbits, laying clusters of 40 to 100 gelatinous eggs in the soil, under rocks, and in outdoor pots. After hatching, slugs can mature in a few months; as adults, they can mate up to six times a year.

• While ridding your garden of slugs is not easy, there are many simple things you can do in the garden to decrease their damage:
• Eliminate their habitat. Garden debris provides a hiding place. Using less mulch will reduce your slug population.
• Hand pick slugs during the evening and early morning hours. Crush them or dispose of them in a bucket of soapy water.
• Add plants such as ginger, garlic, mint, chives, red lettuce, red cabbage, sage, sunflower, fennel, foxglove, astilbe, ferns, mint, chicory, and endive that have foliage and toxins less desirable to slugs. Also consider planting some of the blue type or waffled-leaved hostas that slugs seem to scorn.
• Create a barrier of abrasive material such as crushed eggshells, sand, wood shavings, diatomaceous earth, hair or ash around your hostas. Keep these materials dry and replenish them after it rains. Take care using diatomaceous earth as it may damage your lungs if breathed; use a face mask when applying it.
• Drowning slugs in beer is not as effective as you may think. Dissolving yeast in water can be just as effective and much less expensive. If you choose this option, bury several containers at ground level, empty them and refill them daily. However, you may have too many slugs for this method to be effective.
• Much of the slug’s body is water so they are susceptible to drying out. Cultivate your soil in early spring to expose their eggs to drying air & predators. Try to keep your garden as dry as possible without damaging your plants.
• Iron phosphate baits decrease slug populations without harming birds, small pets or humans. These baits are sold under the name Sluggo, Es-car-go, and Safer’s Slug & Snail Bait.
• Set up a barrier with copper strips or tape. Slugs will not cross the copper. When they slide over it, there is a toxic reaction, similar to an electric shock.
• Attract predators that eat slugs such as ground beetles, frogs, birds, and ducks.
• Lastly, try coffee grounds. Researchers have found that slugs have a real distaste for caffeine. The grounds themselves repel slugs, but a 1 to 2 percent caffeine solution kills nearly all slugs within two days.

I would like to know how to propagate the black gum tree. Is it true that it has a big tap root, so that is why you do not see it a lot in cultivation? What about stem cuttings? Is it hard to root? Would it take a very long time to get a medium-size tree from a stem cutting? Does this species need to be grafted?

The black gum tree (Nyssa sylvatica) is one of our most beautiful trees native to the eastern U.S. Somewhat pyramidal in youth with densely set branches, it grows about a foot a year, reaching about 15 feet in 15 years. It is an excellent specimen tree, acceptable for residential streets, but not in dense urban areas where pollution is high. Despite its outstanding, dark lustrous green summer foliage and its broad range of fall color from yellow to scarlet, it is often passed over.

You are correct that it has a big taproot. However, that probably isn’t the deterrent to more frequent urban cultivation. Balled-and-burlapped nursery stock for early spring planting can be readily obtained. More likely its need for swamp-like conditions, a soil high in organic matter with a pH of about 6.5, and a naturalized setting are what keep it from the current suburban developments. And although its stiff horizontal limbs and irregular bark may endear it to some, its overall irregular shape does not adhere to the script for a manicured yard.

Michael Dirr, author of Manual of Woody Landscape Plants, has raised numerous seedlings from seed. Black gums are generally not rooted from cuttings or grafts. Each half-inch oblong blue-black drupe contains a single seed. The fruit ripens in late September through early October. Since seeds are obtained in the fall, you will need to overwinter them. Dirr recommends using container culture and transplant the second spring while still a very small sapling. The potting mix should be moist, sterilized potting soil, enriched with organic matter. You need to mimic the conditions of a mucky swamp, which means watering the pot very well once the seeds are planted. Place the mucky pot in a large freezer bag and store in a location where the temperature will be near freezing over winter. Germination occurs in spring. Put the potted seedlings outside during the first growing season. Dappled sun is best to prevent scorching of the new leaves. Keep the pots well watered and fertilized. Overwinter in the pots, continuing to maintain the muck-like conditions the black gum loves. Plant out the seedlings in the second spring. To estimate the length of time to a medium-sized tree, you should apply the one foot per year rate.

In a previous issue of Michigan Gardener, mint marigold was mentioned as being able to destroy bindweed and ground ivy. How do I grow it? Is there a better way to get rid of the ground ivy that is overrunning my lawn, garden, driveway, pond, and vegetable patch?

Mint marigold (Tagetes minuta) is a South American herb that grows readily from seed sown directly into the soil once danger of frost is past. It thrives in full sun and will choke out ground elder, bindweed, couch grass and ground ivy as it reaches its full height of six to eight feet. Considered a cash crop in South America for its oil, uses as a condiment and in beverages, it is sometimes considered a weed by others.

If bindweed is a problem in a large sunny area for you, it might be worth a try. However, ground ivy tends to like moist, shady areas as well as sun. For perennial weeds such as these two, there are three types of control: cultural (including crop rotation, such as growing the mint marigold), mechanical and chemical.

As was described in the “Weed Watch” column in the April 2004 Michigan Gardener, to naturally control ground ivy in turf grass, maintain turf density and health through proper culture. Mechanical removal in turf is difficult and rarely effective. Ground ivy is shallow-rooted and it roots at each joint whenever it touches the soil, making it difficult to pull by hand. In beds it can be controlled by diligent and consistent removal. Mechanical removal is accomplished by using a garden fork to loosen the soil about 3 inches deep and gently working the roots out.

To control ground ivy by chemical means, a post-emergent herbicide needs to be used. Pre-emergent herbicides do not work on established ground ivy.