Watering 101: How Much Water Does Your Plant Really Need?
Watering practices are the number one killer of plants. Many people fear they are not watering enough when they are really overwatering. The symptoms of overwatering and underwatering are similar. Here are some tips for keeping your plants in the Goldilocks zone.
How Much
Most outdoor perennials and annuals need 1-1.5 inches of water a week. This amount includes any rain or irrigation the plant gets. When it rains, water less, so the total is still 1-1.5 inches that week.
Of course, sometimes it will rain more than that amount in a week. Water again when the top of the soil dries out. In hot weather, you may need to water twice a week and increase the amount to 1-2 inches each time you water.
Bog and wetland plants will need more water. They have evolved to grow in soil that is always wet. Depending on your climate and the way your yard is landscaped, you may have to water them every two or three days to keep the soil wet.
Cacti and succulents need to be watered when they start to wilt a little. They have evolved in extremely arid regions or places that have a long dry season. The soil should completely dry out before you water these plants again.
Vegetables need enough water to keep the ground evenly moist at all times. Because they grow very fast and produce fruit that has a lot of water in it, vegetables tend to be water hogs. Buying an inexpensive water meter and using it to gauge soil moisture two to three inches deep helps make sure the soil stays evenly moist.
Watering trees and shrubs is a little different. They need infrequent waterings that deeply soak the soil around them. The goal is to get water to the roots that are two and three feet under the soil.
How To Water
The best way to water is using drip irrigation. This method puts water directly into the root zone with very little evaporation. If you don't have drip irrigation, a soaker hose works almost as well.
Overhead watering is the least effective way to water. On a hot day, you can lose 40% of the water that comes out of the sprinkler to evaporation before the water reaches your plants. In addition, watering with a sprinkler gets the foliage wet. Soil may splash onto the leaves and infect the plant with soil borne diseases.
Trees and shrubs need to be watered slowly. Picture a donut that starts about halfway from the trunk to the dripline and goes out to the dripline. Water the soil deeply over the whole donut area. Leave a hose in that area and just barely turn it on until water trickles out. Come back in an hour or two and move the hose to another area of the donut. Repeat until all the soil in the donut is soaked. Don't get water on the trunk or leaves as this can cause rot and fungal diseases.
When To Water
For most perennials and annuals, water once a week during the growing season and less often in the winter when the plant is dormant. If you live in a hot climate, you will have to water twice a week to keep the plant hydrated. Established native plants will not need to be watered unless there is a drought.
Water non-native trees every month all year. Trees that grow in moist areas may need watering every two weeks during a drought as they typically need more water. Water native trees and shrubs during a drought.
Watering New Transplants
When you first transplant anything, water it every day for about two weeks. Gradually start increasing the time between watering until it is once a week for perennials, once every other week for trees and shrubs. Plants will need to be watered twice a week if the temperature is over 90 degrees for more than a few days. New perennials, trees, and shrubs will need supplemental watering for the first three years, even if they are native to the region.
Watering Seeds
Most people only plant vegetable seeds. If you plant seeds in the ground, you will have to water every day until they germinate and grow through the ground to the surface of the soil. If the seeds dry out before then, they will die. Tender new plants will need watering every day until they are older, and their roots have been established. Gradually extend the time between waterings until you water once a week. If the weather is hot, you will need to water the plants twice a week.
Mulch
Mulch is essential to water management. Putting three inches of mulch in a donut around plants helps keep the soil moist by reducing evaporation. Mulch itself gets wet and holds water. It gradually releases the water into the soil as the soil dries out. In addition, mulch helps prevent weeds from sprouting and stealing water from your plants.
Never let mulch touch your plants. For trees and shrubs, start the mulch about three inches from the trunk and mulch to the dripline. For everything else, leave an inch around the stem mulch-free.
If you live in a cold climate, rake the mulch to one side in the early spring to help the soil warm faster. Replace the mulch after the soil warms. Be sure to remove the mulch before planting seeds. Replace the mulch when seedlings are at least four inches tall.
Group Plants With Similar Water Needs
When designing your landscape, be sure to group plants with similar water needs together. For example, you would not plant something like marsh hibiscus under a white oak tree. If you watered enough to keep the marsh hibiscus happy, the oak tree would get root rot from the constantly wet soil.
Instead, plant things like Virginia bluebells under the oak tree. Virginia bluebells are adapted to the dappled light and moist, but not wet soil around white oaks. Group perennials that need very moist soil together. Set the ones that like less water together in another area. By doing this, all of your plants will have a chance to thrive.
Symptoms Of Trouble
The symptoms of underwatering are wilting, drooping, turning yellow, and dropping off the plant prematurely. In trees, bark may crack, branches may die back, and leaves may fall. Constant but mild water deficits may cause the tree or plant to be more susceptible to pests and diseases. The plant does not produce as many flowers or fruit, either.
The symptoms of overwatering can look similar at first. Plants may wilt or droop. Leaves may turn yellow and drop off. Fungal diseases thrive in wet soils. Prolonged wetness will cause the roots to rot, leaving the plant unable to take up water. This is when you see wilting or drooping. Once the roots have rotted, the plant will die.
We Can Help
Garden Plants Nursery can help you choose plants that go well together. We can also answer any watering questions you may have. Give us a call at 931.692.7325 today.