UNITED STATES—In a region of so much nice sunny weather and minimal rain, sogginess should not often be a problem. Getting enough water to plants that want it is the more obvious concern. However, even here in California, many gardens have areas that are, for one reason or another, a bit soggier than they should be. Finding plants that tolerate extra moisture can be tricky, especially since soggy areas are likely to be soggy only during a specific time of year, but can get dry at other times.Oddly, the soggy time of year is not always during rainy winter weather. Low spots in or near lawns are often more saturated while lawns require regular irrigation during warm and dry summer weather. Atriums that are below roofs or eaves also tend to get more water during summer because they are not exposed to rain when irrigation gets decreased for winter. Maintenance gardeners usually irrigate excessively, especially where coverage is a problem. Unfortunately, the driest part of a lawn dictates how much water the rest of the lawn gets.
Excess moisture tends to accumulate in low spots, where broadcast irrigation overlaps, and against foundations and walls. It dries slower in shade and where dense soil drains slowly. Willows, poplars and other trees with extensive root systems and high evapotranspiration rates (evaporation from foliage) keep soil significantly drier, but have aggressive roots.
Only bog plants like papyrus, reeds, baby tears and some types of iris, cannas and sedges tolerate saturated soil. Willows, sycamores and red twig dogwood do not mind saturation if they get to drain sometime during summer. Japanese anemones, calas, fuchsias, impatiens, ivies, houttuynias and some types of ferns tolerate quite a bit of excessive moisture, but only if the soil sometimes drains enough to allow some degree of aeration. Azaleas and camellias seem to tolerate dampness, but really prefer good drainage, and can rot suddenly without it.
Although Lily-of-the-Nile, Heavenly bamboo and Oregon grape do not need much water, they are remarkably tolerant of excessive moisture as well. Several types of eucalyptus and melaleucas survive flooding through winter if water recedes by summer. Otherwise, the most drought tolerant plants are also most susceptible to rot in damp conditions.
Highlight: Houttuynia Cordata
In nurseries, most Houttuynia cordata are variegated with creamy white, with pinkish new foliage. In gardens, most are rich green without variegation. They are just so susceptible to reversion! This reversion is not much of a problem though, since green plants are just as handsome and woodsy as variegated plants are. Sometimes, while in transition, both variegated and green plants mix together. The green leaves are a bit larger, with slightly larger white blooms in summer. However, even the larger flowers are only about an inch wide, and have only four or maybe as many as six petals (bracts). Individual leaves are only about one to three inches wide and about half an inch longer.
The perennial stems spreads out over moist soil like a small scale ground cover, rooting as they go. The tips of the stems stand about half a foot tall, and can get two feet tall in shade. Propagation by division is quite easy.
By Tony Tomeo
