Across the Director’s Desk

Container gardens are one of the hot trends in horticulture and some of the best plants for containers are tender perennials. Tender perennials are grown in Iowa as annuals even though they're perennials in their warmer native climes.

Tuberous begonias come in a wide variety of color and flower forms. Most grow 8-12 inches tall. Some are upright or mounding, while others will cascade over the side of the pot. These plants would prefer a slightly shaded location and may scorch in the heat of the noonday sun. They also need a well-drained soil, so planting them in terra cotta pots with a soil-less mix will give the best results.

For an early start, tubers can be planted indoors in a sunny window or under lights and transplanted to an outdoor location after all danger of frost is past. They can be grown from seed, but tubers are readily available at most

garden centers and will give much better results. The NonstopT hybrids will handle heat better than most. It may be difficult to tell which is the top and bottom of the tuber, but the concave side goes up and the rounded side goes down.

Dahlias are native to the mountainous regions of Mexico where the never get to experience the joys of winter. So they are often grown in Iowa as annuals, even though they can be over-wintered indoors in a cool location.

The dahlia was discovered by a botanist named Andrew Dahl. If you notice a similarity here, it's because plant names ending with "ia" are often named after the discoverer or in honor of a noted person. Begonia, Petunia, Forsythia, Lobelia, Zinnia, and Jeffersonia are a few examples.

There are literally thousands of cultivated dahlia varieties with flowers ranging from small pom-poms to 16 inch "dinner plate" dahlias. Of course, to get flowers of that size, dahlia aficionados disbud the smaller secondary buds behind the main bud. Dahlias have a reputation for being high maintenance, and they are if you're growing them for exhibition. But dahlias can also be grown as bedding plants. Some varieties can even be started from seed. They need as much sun as possible and a cool, well-drained and fertile soil. Dahlias like moisture, but a wet soil sounds the death knell.

Determining the difference between "moist" and "wet" is the hard part. To solve this problem, consider growing them in containers. You'll have a better opportunity to manage moisture, sunlight and fertility.

In addition to tuberous begonias and dahlias, there are other tender perennials that can be grown in Iowa. Gladioli are the most popular, but caladium, calla lilies, and cannas will also thrive. Since they are tender perennials, they need to be dug up and stored in a cool (but above freezing) location during the winter. With proper care, they will last for years.

For more information on these topics, contact the Extension office for a copy of RG 311 "Growing and Over-wintering Tender Perennials" or RG 315 "Dahlias."