We have become so accustomed to coping with drought, rain can present new challenges. For all Californians, the rain is welcome, but particularly so for farmers and gardeners. Free water, without salts or chemicals, is perfect for crops and all plants. In addition to using rainy days to plan for spring planting, there are some garden tasks to keep on our list. After the storm, there are areas of the garden to check for problems, damage and potential pest issues.
Most plants do not like to have their roots in water. Trees and plants in general benefit from the rain washing dust off their leaves, in addition to the healthy irrigation. The pore spaces in soil normally provide air in addition to water for healthy roots and beneficial soil organisms. Plant roots need oxygen to survive, and sitting in pooled water for a length of time can kill the plant. They can also develop fungal root diseases if there is standing water and mud at the soil line around the base of the plant. Note where this occurs and provide drainage of the excess water away from the plant. Also check container plants and saucers under plants for standing water.
Plan for the future to divert water from gutters and other runoff into areas of the garden where it can soak in using dry creek beds. On the Master Gardener web site, there is a newspaper article on developing a dry creek bed in your garden. There are also online resources for developing a “rain garden” to collect water in wet seasons and safely soak in to replenish the ground water. The search for ucanr.edu/sites/raingardens will provide steps to develop a rain garden and suggested plants to conserve water and prevent topsoil loss.
If you have areas of pooled water, taking a picture with props such as a ruler or yardstick for depth and to mark the borders of the water can be valuable in your plan for correcting the problem. A French drain system diverts water away from where it can do harm, such as near the house foundation. Another reason to provide a route for rain runoff is the risk of chemicals which were applied to lawn areas collecting in puddles or diverting into creeks and streams. Some chemicals are toxic to animals or aquatic life.
Check for broken tree limbs, as water-soaked branches are more prone to breakage in the wind. A large broken limb leaves an open wound in the bark, and the moisture from rain can leave an opening for disease. Cutting off the jagged edges and leaving a clean pruning cut is better for the tree.
Weed removal is much easier after rainfall. When weeding, it is always best to dig out all of the weed roots. In dry soil this is difficult, so remove weeds now while the soil is still moist. Shallow small weeds can be dislodged with a hoe and their roots will dry when the sun comes out. The rain will foster new weed growth, so this is an ongoing process. Layers of mulch around plants will prevent weed seeds from getting sufficient light to germinate. On the Master Gardener web site, UC IPM has a weed identification tool. ipm.ucanr.edu/PMG/weeds_intro.html
Check out the UC Pest Notes on the web site. Moisture in the soil will bring out unwanted visitors, such as slugs, snails and earwigs. There are pest notes covering details of coping with them and other pest issues. Small containers, such as a tuna can, filled with cooking oil will attract and trap these critters. It’s a bit ugly, but effective and nontoxic. The baits for snails which contain iron phosphate are nontoxic for pets and people. Avoid baits containing metaldehyde if children or pets can access the area bait is applied—it is highly toxic. Always read the caution label on any product used in the garden.
Check the leaves on plants and trees for fungal diseases after a number of rainy days. Fungal spores from the soil can be splashed up into the plant and cause disease. Prolonged wet leaves can promote rust and black spot on roses. When pruning roses, try to create a vase shape, with the center fairly open for better air flow and faster drying when the rain stops. Check for mulch piled up against the crown of the plant or tree, as this will hold moisture and promote disease.
Avoid walking in wet planting beds which increases soil compaction. If it is necessary to walk in wet areas, use a board or cardboard to distribute your weight more evenly. Providing a walkway around the border of planting beds with a thick layer of mulch also keeps the mud off your shoes.
Erosion causes more than a mess. In addition to a muddy mess under foot, erosion from heavy rainfall can expose tree roots, leading to a fallen tree, or loosen rocks and mud leading to a rockslide. Erosion also washes away topsoil, a valuable commodity. Topsoil contains healthy organic matter from the decomposition of leaves, tree bark and plant material. The microorganisms in topsoil support plant growth. Topsoil is 2-8 inches deep, so even a small amount of erosion can be significant. In addition to diverting the flow of water in a more desirable direction, a sloped area may need to be terraced to slow the flow of water in a heavy rainfall. Planting small shrubs, especially native plants with their long tap roots, can provide a support for the soil.
After the storm has passed. Once the soil begins drying, check for soil moisture using a moisture meter or digging down a few inches before resuming your watering schedule. Especially under mulch, the soil may remain wet for some time. If you find any garden produce touched by flooding or lying on the ground, it is safer to discard it in case it has been contaminated by runoff from roadways, pasture or septic systems.
Take some time to enjoy the lovely green on the foothills and spectacular view of the mountains. Our gardens are enjoying this deep watering to establish good root systems for their spring growth spurt.
The Master Gardeners will be live to answer your questions on Saturday, April 1, 8 to 11 a.m. at Visalia’s Farmer’s Market in Sequoia Mall’s southwest parking lot. You can also contact them at 559-684-3325, or visit their web site at ucanr.edu/sites/UC_Master_Gardeners.