Give Tubers a Try

At this time of year, both public and private gardens are alive with the color of spring-blooming bulbs. Yellow and white daffodils and many-colored tulips mix with shrubs like Ribes sanguineum (Red-flowering Currant), and Camellia japonica, to make a fine show and provide sources for fabulous cut flower arrangements. But the color-riot doesn't have to end with spring, if you plan now to plant summer-blooming bulbs, and especially tubers, which grow very well in containers.

When I think of tubers, I think of french fries, and indeed potatoes are tubers. Tubers are fat underground stems, and the plant grows out of it. These plants are sometimes lumped together with "bulbs," but actually bulbs are different. Bulbs have fleshy scales usually surrounded by a papery tunic. Daffodils and oriental lilies are bulbs. Corms have solid center tissue instead of scales, with crocus and freesia falling into this category. Rhizomes are thickened stems that usually grow horizontally near the surface of the soil; Calla lilies and bearded iris are included in this group. All of these "bulbs" don't look like much when you plant them--a lumpy brown sort of thing--but what a surprise they hold.

One tall beauty that I've grown in a pot is Canna (Cannaceae). They range in size from three to even six feet tall, and their foliage add height to a container composition. They also provide colorful flowers as well. (Mine, a mislabeled yellow variety, were less tall--closer to two-plus feet.) Their shiny green leaves and elongated oval shape provide a textural contrast to other plants in a mixed container. They enjoy a sunny location and heavy watering during flowering, and are best planted about five inches deep in loose soil. Because tubers are often native to the tropics and subtropics, they will need to be lifted in the fall and washed, then allowed to dry on newspaper for several days until all the moisture is gone. After, store them in peat moss in paper bags over the winter. I put mine in a downstairs pantry where it stays dry and cool but not freezing. Remember to label the bag as a final step so that next spring you'll know what it is.

Another glorious tuber that produces amazing foliage is the Caladium bicolor (Araceae). Two that I tried last year are 'Fannie Munson,' with a pink and white speckled background and red veining, and 'Blaze,' with deep burgundy centers, dark green edges and red veins. This plant is not grown for flowers, but for the large heart-shaped, colorful leaves. It works well in the middle layer of a pot because it reaches around eighteen inches in height. There is a variety with white speckled leaves called 'Candidum' that I have my eye on to try this year. Imagine this as part of a black and white combination with Ophiopogon planiscapus 'Nigrescens' or black mondo grass, perennial Cimicifuga simplex 'Brunette' with black foliage and white flowers, and finishing with some trailing Lysimachia nummularia 'Aurea' or golden creeping jenny, all in a shiny black container.

Last year was my first experiment with the wonderful tuber Ipomoea batatus 'Margarita,' or Sweet potato vine. It looked innocent enough in its four-inch pot when I bought it, and I planted it out in my container. The stems eventually grew to a length of about three feet long, covered with heart-shaped chartreuse leaves. It does like full sun, and provides a vivid contrast to darker-leaved companion plants. There is a variety called 'Blackie' which has dark purple leaves and stems, if you are looking for a dark contrasting leaf color. If you want a trailing plant to cascade voluptuously over the edge of a pot, this is the one for you.

It's pretty easy to arrange plants in a pot if you use a tall one as a focal plant, and then surround the tall one with medium sized ones to fill in the middle of the pot, and finally put trailing plants all around the edges, to end up with a nicely opulent container. I put the canna in the center, and surrounded it with the caladium, coleus in deep burgundies that I started from seed, and a pink pelargonium for its non-stop flowers. I also included in the middle layer some black mondo grass and a burgundy chrysanthemum along with some dusty miller. Trailing verbena in soft pink joined 'Margarita' flowing over the edges, and to them I added golden creeping jenny for yet another shot of a chartreuse trailer but with a smaller, different leaf shape for variety. I was careful to not let the planting ever get dried out, so I watered it everyday and I fertilized it every one to two weeks. It put on a glorious show until frost killed off the tops of the tender plants. I cleaned and stored the tubers as I already mentioned above for cannas, and I'm ready to go for putting these fantastic tubers in this year's containers. For knockout foliage plants suitable for container growing, give tubers a try.

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