ASK A MASTER GARDENER
■ Dear Master Gardener,
I am looking for a native shrub that is a bit unusual to plant at the edge of our woods. A neighbor suggested a witch hazel but I know nothing about it. What do you think?
Answer: Witch Hazel (Hamamelis Virginiana) is unusual because it is perhaps the only native shrub which blooms in the late fall after other deciduous plants have lost their leaves. It is a small understory tree/shrub that is hardy from zone 3 to zone 8, reaching a height of up to 25 feet but more commonly grows to 12 to 15 feet with a spread similar to its height. It has crooked, spreading branches and handsome 3-6 inch dark green leaves, similar to hazelnut leaves, that turn bright yellow-gold in the fall. It likes moist, loamy soil but tolerates drier soils, too. The yellow, fragrant, spidery flowers emerge in mid-October and last a month or more, forming a bright spot in the leafless woods. The seedpods are also unusual in that they take a full year to mature then burst open forcibly, shooting their shiny black seeds up to 30 feet away.
Witch Hazel has an interesting history, having been used by Native Americans and early settlers medicinally. An extract distilled from its bark has astringent properties that were used for skin diseases, insect bites and aftershave lotion. The “witch” part of its name comes from its supposed ability to “witch” (find) water with its forked twigs.
This attractive and unusual native shrub would be a good choice for your woods. It is underused and may not be readily available in nurseries. If local nurseries don’t carry them, try mail order sources.
■ Dear Master Gardener,
What is the “lasagna gardening” method?
Answer: Lasagna gardening is an easy, organic, no-dig method of creating a garden bed. It is called “lasagna” because like the lasagna you eat, you build layers of organic material that break down and create a rich soil. Lay a hose or rope down to mark the area of your new garden bed. You do not have to remove any sod or weeds. Put down 3-5 layers of newspapers making sure to overlap them. You could also use cardboard. Then wet the newspapers to keep them in place and begin the decomposition process. Next, cover the newspapers with organic material such as shredded wood mulch, peat moss, grass clippings, chopped leaves, pine needles and/or compost. You will smother the grass and weeds without any tilling, digging, or back-breaking work. The only digging you will have to do are the holes for your new plants!
■ Dear Master Gardener,
What is the difference between a sweet potato and a yam? Is one more nutritious than another? Can we grow them in Minnesota gardens?
Answer: What are sometimes called yams in parts of the United States and Canada are actually sweet potatoes. They are sometimes used interchangeably; however, the U.S. Department of Agriculture requires that the label “yam” be accompanied by “sweet potato.” Yams and sweet potatoes are botanically different and not even remotely related. Yams belong to the genus Discorea and the family Dioscoreacea; while the sweet potato, Ipomoea batatas, belongs to the Convolvulaceae family, which is in the morning glory family. The sweet potato is not related to a potato either, as the potato belongs to the Solanaceae, or nightshade family.
Yams are only grown in the tropics. It is highly unusual to even find actual yams in U.S. supermarkets, but if you did, they are a good source of potassium, manganese and vitamins C and B6. Sweet potatoes are grown in the U.S. and are a good source of potassium, manganese, copper, iron, and vitamins A, C and B6. Sweet potatoes are commercially grown in the southern U.S. because they require a long frost-free season. The growing season varies from 90-150 days (120 days for Jewel), depending on the cultivar. If you want to put some effort into it, you could definitely try growing sweet potatoes. Always buy certified disease-free plants. Slips can be purchased through a reputable mail-order company or you can try to produce your own. Some varieties you could try are Beauregard, Porto Rico, Centennial, Georgia Jet and Jewel.
If you would like to produce your own slips, choose a smooth, well-shaped root approximately 1-1/2 inches in diameter, from the previous year’s harvest. Place the roots in clean sand covering them with another two inches. Water thoroughly and continue to water regularly to prevent the roots from drying out. Keep the temperature between 75-80° F. Slips are ready for transplanting when there are 6-10 leaves present, or in approximately six weeks. You could use a store-bought sweet potato to produce slips, but you would not know what cultivar you have or if it is suited to growing in Minnesota.
After the last frost, plant the slips 12-18 inches apart with 3-4 feet between rows. You may want to elevate the rows and use black plastic as mulch to help capture more of the sun’s heat. Keep the sweet potato plants moist and avoid watering them for 3-4 weeks before harvesting. Allow the roots to dry on the ground for 2-3 hours, and then cure them at 85° F., with 85 percent humidity for 10-14 days. This process helps the skin to develop a protective layer, which will decrease any disease problems during storage and will keep the tubers from drying out. Be careful handling them because they bruise easily. If a hard frost is coming, cut off the vines and do not allow the roots to freeze. Sweet potatoes should be stored in a cool, dark place, ideally around 55° F. and never stored in the refrigerator.
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.