February 26, 2012

Maine Gardener: Taking an annual approach to perennials

Maine's backyard gardeners mostly deal with perennial plants. They are generally both easier and less expensive than annuals. You plant them once, and they come back every year.

Dennis Schrader, co-owner of a greenhouse operation on Long Island in New York, told an audience at New England Grows in Boston earlier this month that a few annuals included in the mix can make a garden a lot more interesting.

"You aren't limited to bedding out or a stacked wedding cake of plantings," Schrader said. "Take a more adventurous look."

The typical garden, he said, has some height in the back, some mid-level plants and some filler. But if you walk through your perennial beds, you can see how the shapes and colors of annuals could fit in.

Time for a definition here. What we in Maine call "annuals" come in two different types. True annuals are plants that last only a year no matter where you grow them. You put in the seed or plant, it grows and produces seed in one year, the plant dies back, and the seeds produce new plants for next year. An example is the sunflower.

Most of the plants treated as annuals in northern climates are tender perennials or tropicals. In warmer climates they would come back every year, but here in Maine, the cold weather kills them every winter.

"These plants add a whole new dimension to your garden," Schrader said. "They have different shapes, and they bloom all summer long."

A lot of the tropicals are grown for their unusual foliage rather than their flowers. An example is Colocasia "Thailand Giant," which has the common name "elephant ears" and which Schrader sells in 5-gallon pots. This plant will grow 8 or 9 feet tall, and each leaf will grow 5 feet long and 4 feet wide. A plant like that will draw some attention in a Maine garden.

Schrader said these plants, which can seem expensive, can be overwintered.

"You can put them in a cool basement or a garage that won't freeze," he said. "You can put them under the dining-room table all winter. And a fallout shelter works. Then you plant them the next spring."

Schrader's audience at New England Grows included a lot of people who work in plant nurseries, and he said their customers might be reluctant to buy an expensive plant. But telling them they can save it from year to year might convince them to spend the money.

"Then fall will come and, well, they won't bring it in, and you can sell them the plant again next year," he said.

Palm trees are not common in the North, but Schrader said the "Windmill Palm" Trachycarpus fortunei would be a focal point in a garden or on a patio. In nature, it could grow 40 feet tall, but would be much smaller in a pot and would also have to go indoors for the winter.

Cannas have grown more popular for use in Northern gardens in recent years. The foliage is big and bold, and they will produce flowers when planted in pots or in gardens in Maine.

But they also have great leaves, and they look good even if they don't bloom. Several that he likes include "Pretoria," "Tropicana" and "Intrigue." 

Cassia didymobotrya "Popcorn Bush" is another bold plant that is a shrub in its native habitat, but can grow to 8 feet in a single season. It produces bold yellow flowers that smell like buttered popcorn when touched.

"The cassia bush can intertwine and form a hedge in just a few weeks," Schrader said.

Formosa lily will produce white flowers up to 10 inches long on a stock that can get up to 6 feet tall. Once the flowers go by, the seed pods also are interesting.

An unusual plant Schrader recommended is Gossypium herbacum nigra "Black Cotton," a black-leaved cotton plant that also produced black cotton balls as flowers. It will grow well in a single season.

Coleus is a more commonplace annual, and Schrader uses it massed together with several different varieties for a display of color. This can work as a lesson in hybridizing plants, because coleus seeds profusely, and the varieties will cross-pollinate. In his greenhouses, there are all sorts of potential hybrids growing on the floor from spilled seeds, and the same could happen for you in your garden.

There are a number of tropical vines that also will work well in Maine gardens, Schrader said. 

One of the most vigorous is Argyreia nervosa "Woolly Morning Glory," which is so vigorous that it has been compared to kudzu, but it is not related to kudzu. But if you want some vines that will cover everything and definitely die at the end of the year, this would be the one you want.

The way a lot of people in the North use tropicals and annuals is in container plants. With containers, it is easier to bring them inside for the winter. You don't have to dig them up and repot them, because they already are in their pots.

And while one container will look good, Schrader recommends grouping several together to make a sort of container garden on your patio, deck or entrance steps. Grouping several small containers together will make a strong statement in the garden.

No one is saying you want to give up on your perennials, but a few bold tropicals can make a Maine garden more memorable. And Mainers are thrifty enough to bring their tropicals inside in the fall. Our blue passion flower has survived two winters, and (I just checked) it looks like it's going to make it through this winter as well.

Tom Atwell has been writing the Maine Gardener column since 2004. He is a freelance writer gardening in Cape Elizabeth, and can be contacted at 767-2297 or at:

tomatwell@me.com

 

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