February can be a rainy month in the garden

Richard Bogren, Gill, Daniel J.

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For Release On Or After 02/12/10

By Dan Gill
LSU AgCenter Horticulturist

February weather often includes heavy and frequent rain, which reminds us that Louisiana has a relatively wet climate. Periods of drought certainly do occur, especially during the hot months of summer. But it is important for gardeners to realize that plant selection and the gardening techniques we use are largely influenced by the generous amount of annual rainfall we receive.

Periods of rain saturate the soil with water. And for most plants, it’s important for the water to drain away efficiently. Other than those adapted to bog or swamp conditions, plant roots need oxygen in the soil. They can literally drown if the soil stays saturated with water for extended periods. So plant in beds that are raised somewhat above the surrounding ground level. Beds are typically raised about 6 to 12 inches, which allows the water to drain from the soil faster.

Raised beds work well in handling a heavy rain, such as when 2 or 3 inches (or more) fall in a single day. What is more difficult to defend against is frequent rain over an extended period. Frequent rains do not allow the soil to drain, since every time the water from one rain drains away another rainy day quickly comes along to saturate it again.

Another danger to a plant is too much rain. Fungal disease organisms that attack plants and cause root rots and crown rots are far more likely to cause damage when the soil stays wet. This occurs partly because a plant’s roots are weakened if they’re deprived of the oxygen they need. But these fungi also prefer and are more active in a soil high in moisture. So, plants growing in beds saturated with water for extended periods are prone to root and crown rots that can be disastrous because these diseases often are fatal.

Fortunately, excessive rain in February is not so dire. Many plants are still dormant, which makes them more forgiving of the saturated soils. Roots are not as active and will better tolerate reduced oxygen levels. In addition, the fungal organisms responsible for root and crown rots are not nearly as active when the soil is cool. So despite frequent rains and wet soils, we generally do not see major problems this time of year.

If this were July, the situation would be quite different. Root rots are common when rainy weather occurs during the hot months of June, July, August and early September, and they can be devastating. We can, however, see some negative effects in some plants as a result of February rains.

First, the flowers of cool-season bedding plants that produce relatively large blooms, such as pansies and petunias, really get hammered by the rain. Pinch or cut off these damaged, unattractive flowers if possible. These plants will recover when the weather turns drier. It is possible to see some rot occurring to cool-season bedding plants because they’re in active growth now, but it isn’t typical.

Caladiums are tropical plants that thrive in shady beds during our hot, humid, rainy summers. Because our soil never freezes, we have the option of leaving caladium tubers in the ground over the winter. However, we don’t always get away with this.

Although caladiums enjoy abundant moisture when they are in active growth, they prefer to be dry when they are dormant – their ancestors developed a dormant period to survive the dry season in their native Brazil. Exceptionally wet winter weather, such as we may experience in February, can cause the tubers to rot. This is why, even though we can leave the tubers in the ground over winter, it generally is more reliable to dig them in fall and store them indoors during the winter. If you left your caladium tubers in the ground and they don’t show up by the end of May, you will know why.

Typical wet February weather should also remind us to be cautious about using plants native to dry climates unless they have a proven track record in our area. It’s true that we do have periods of drought during most summers, so gardeners sometimes are interested in landscaping with plants that grow in dry climates, such as in the southwestern United States. But these gardeners must not to forget that we garden in a Gulf Coast, warm, humid climate, and on average we get plenty of rain. Even in a relatively dry year, one major rain from an August hurricane can kill off dry-climate plants.

Because we tend to get abundant rain, never forget to consider drainage when designing beds and choosing plants. Raised beds are generally the best way to ensure good drainage. If you have a low area that tends to stay wet and you don’t want to put in a raised bed, you can landscape the area with plants that enjoy wet soils. It is often better to choose plants adapted to an area’s drainage rather than try to radically change it.

Even with good drainage, you must choose plants that are adapted to the rainfall we get. If you read a plant description that indicates a plant prefers to be dry in winter, it will have difficulty thriving in our climate. Although occasionally we may have relatively dry summers, you can pretty much rest assured that we will generally have abundant rain during our winter months.

Rick Bogren

1/4/2011 1:14:45 AM
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