Dealing With Drainage Issues
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Over the past few weeks, master gardener Paul James's garden has experienced steady, consistent rains. As a result, his garden has suffered in various ways. The most obvious is flooding. Just last week, one area of his yard had water standing knee high.
The nearby storm drain wasn't clogged, but the sheer volume of rain that fell – two inches in one hour – was more than the drain could handle at once. Also at least 30 bags' worth of mulch washed out onto the lawn (figure A), and cleaning it up wasn't easy. Elsewhere in his yard, the washout was just as bad, if not worse.
Prior to the recent rains, Paul had already invested a lot of time and money trying to resolve several drainage problems in his garden. For instance, a dry stream bed (figure B) at the front of his yard helps carry runoff from a neighbor's driveway to a city drain.
Another dry stream bed takes water from another neighbor's backyard to another city drain. Paul covered this large and unsightly drain with a decorative and functional bridge a few years ago (figure C). Also, downspouts are connected to underground pipes that channel water away from the patio and the planting beds next to the house.
Although some of his efforts have paid off, others haven't. In one area of his garden, Paul installed drains connected to buried flexible pipe. Unfortunately the soil around the drains has washed out so badly that they don't really work anymore (figure D).
Another area of concern is the pond stocked with koi. On the one hand, rainwater is good for a pond. But too much of it can upset the natural chemistry of the pond water.
Paul maintains a salt content of roughly 0.13 ppm (figure E) in his pond. This salinity rate is good for the koi and helps control algae. The rainwater and resulting runoff has diluted the salt content, however, so he needs to add more.
Paul also needs to add more beneficial bacteria for the same reason. He ordinarily does this every week anyway, but because the rainwater has diluted the concentration of bacteria, he needs to inoculate the water more frequently than usual.
Excessive rains can result in a rapid explosion of mosquitoes. Make sure to empty plant saucers, wheelbarrows and anything else that collects rainwater. Standing water provides a breeding ground for mosquitoes.
"Wet feet" on potted plants
Too much rain can also have an effect on plants because the majority of plants don't really care for wet feet. That's especially true of cacti and succulents, which can die if their roots stay wet for extended periods. For that reason, Paul moves his potted succulents to a covered but sunny area to let them dry out.
Although containerized plants appreciate the rain and it's nice to not to have to water them every day, several days of rain in a row means a lack of sunlight. This can lead to stunted growth and flowering delay. Incessant rains also wash many nutrients out of the potting mix in the containers. So as soon as there is a dry period, provide containers with a good dose of fertilizer.
Soil drainage in planting beds
Because he has amended his planting beds with soil amendments like compost that promote good drainage, Paul isn't concerned about the health of his established garden plants. He also planted them all at the proper depth, slightly above grade, so that their roots wouldn't suffocate in the waterlogged soil.
After it rains, weeds seemingly pop up everywhere. Although weeds are easier to pull when the soil is wet, unfortunately the ground is so wet that it can be difficult to get in the beds to pull them. For this reason and because he doesn't want to compact the soil, Paul prefers to weed the edges of his beds and wait to weed the interior parts until later.
Mowing the lawn
When rains prevent you from mowing the lawn, all you can do is wait for a dry spell and be prepared to mow not once, but twice. First, adjust the mower deck to its highest setting and mow. A day or two later, drop the deck one notch and mow again. Cutting the grass when it's wet and removing more than one-third of the top growth each time you mow are two of the quickest ways to ruin a lawn.
Master gardener Maureen Gilmer discusses the advantages of water gardening.