Q Are the hazelnuts I remember picking in northern Wisconsin as a kid the same thing as the expensive filberts that decorate some cocktails? Where can I find hazelnut plants?
A The names hazelnut and filbert are often used interchangeably. The plant you grew up with was American hazelnut (Corylus americana). This large shrub grows natively in northern Minnesota and Wisconsin. It produces small edible nuts in unusual frilled sheaths which turn brown in late summer. The nuts are a favorite food for squirrels, wild turkeys and other wildlife, as well as for people.
The nuts that are sold commercially as hazelnuts or filberts generally come from hybrids of a different species, the European filbert (Corylus avellana). This plant is less hardy but produces larger nuts. There are many filbert orchards in Oregon and Washington. A number of hybrids between the American and European species have been developed, combining better hardiness with larger nut size.
American hazelnut plants are available from several local nurseries, especially those that feature native plants. Many of the hybrids are available by mail order from Bear Creek Nursery, Box 411, Northport, WA 99157.
Q I planted some perennial flowers in large pots this summer. What do I need to do to overwinter them?
A Many annuals, perennials, vegetables and small shrubs can be grown in decorative containers in summer. Potted annuals and vegetables are usually thrown in the compost pile at the end of the season. Perennial plants (including herbaceous perennials and woody plants such as shrubs) can be kept from year to year, but they need special care to make it through the winter.
The key to overwintering potted perennials is to keep the roots from freezing. If you have any open garden space, or a spot in the corner of the yard where you can dig a hole, you can overwinter your perennials in the ground. If your perennials are growing in a plastic container, sink the whole container into the soil, all the way up to the top of the container. Do this in midfall, before the ground starts to freeze. However, you can't bury terra-cotta pots because they will break if they freeze. Instead, tip the plants and the whole root ball out of the container, then sink the root ball into the soil and store the pot in the basement. After the ground starts to freeze you can pile some straw or dry leaves over the plants in the garden for extra protection. Dig the potted plant or root ball out of the soil in the spring and repot it for the summer.
If you don't have garden space, you can try another method for protecting the plants. In late fall, put the entire container in a large, heavy plastic garbage bag, then fill the bag, around and over the container, with loose dry leaves or straw. The bagged container then needs to be stored in a spot that is cold, but not colder than about 25 degrees -- 30 to 40 degrees is ideal. Most modern basements are too warm, but old-fashioned root cellars will work.
I've had good luck overwintering a small potted Japanese maple and several other woody plants in my unheated attached garage by bagging the pots as described, then pushing the bags up against the house side of the garage where it stays warmer. Unbag and move the plants back outside in the spring.
-- Nancy Rose is a research horticulturist at the Minnesota Landscape Arboretum. She spends her spare time gardening, inside or outside, depending on the weather. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.