By Carol Crupper
The Annual Bog
Impatiens flowers are annuals, which need to be planted in the garden each year. |
When Cheryl and Jim Harmon planted their new gravel bog filter in Lawrence, Kansas, they went wild. The scene included three hibiscus bushes, taro, forget-me-nots and a generous sprinkling of yellow iris. It looked beautiful!
The following year, they were sorry they had planted so much. The hibiscus had tripled in size — and worse, the yellow iris had entangled its roots so tightly into the gravel and pipe that pond water couldn’t flow through. It took days to clear the mess. Today, the yellow iris is gone, along with most of their other perennials — which have been replaced by a simple assortment of bog-friendly annuals.
So when it comes to planting your bog, what should it be: perennials or annuals? It depends who you talk to.
Cheryl Harmon suggests that though there appears to be an equal choice in the variety of plants available for the bog, there is a huge difference in the amount of upkeep involved. “When perennials are left in place over one year, their root systems quickly fill up the bog material, making water circulation difficult. It also makes removal and division a big job.”
Annuals are easier to maintain because they die out and are replaced each year. There is a higher cost for replacing the plants, but the benefits are less work and the time saved. Changing out annuals each year also offers an opportunity to try a larger variety of plants until you find your favorites. A good compromise may be to have several perennials and to fill in the rest with annuals.
The Perennial Bog
Mike Parmley, who designs, builds and maintains ponds and water features in the Lawrence area, suggests the opposite of Cheryl Harmon. He says that fast-spreading annuals like yellow flag iris are great for a bog garden. He says, “Yes, you must divide it regularly (perhaps even twice a year), particularly when it’s grown in full sun. But the iris works quickly to clear up a pond, and unlike cattails, it clumps rather than runs. If you stay on top of it, it’s fine.”
Parmley likes perennials in a garden. In colder climates, annuals cannot be planted until early May, which leaves the bog filter empty for a good part of the year. “Perennials give us more bang during the early season,” he says.
Parmley likes to mix annuals (such as impatiens, sweet potato vine and Thalia) to complement a core stand of hardy perennials (including iris and day lilies).
The Harmons, on the other hand, lean heavily on annuals. Favorites include imperial taro, red cardinal flower, variegated society garlic, curly Juncus effuses ‘Big Twister’ and long-stemmed Thalia. Cheryl likes plantains, too. “I like the leaves and flower spikes,” she says.
Despite their penchant for annuals, the couple elected to keep several perennials, including one ‘Texas Star’ red hibiscus, to anchor the garden. They also kept some ‘Gerald Darby’ blue flag iris, with dark, arching stems and roots that are easier to pluck out.
Above all, they’re keeping the look simple. “What happened was a jungle. I couldn’t see anything on my berm,” Cheryl says. “Plants need a little breathing room. To get maximum circulation, give your plants plenty of space and don’t overplant.”