This is not a typical summer for Larchmont. Due to one of the wettest Junes on record, we are seeing green lawns and generally lush plants in July and the beginning of August. But we may also be noticing certain diseases on our plants, such as late blight of tomatoes, which can be spread by rain and wind.
How much should we be watering? Except for a few of my container plants and some newly planted flowers, I did not water during June and have done little watering since. If you have an automatic sprinkler, I hope you have a moisture or rain sensor so that you are not watering unnecessarily.
So how do we determine the amount of water needed for our plants?
Watering is all about achieving the right balance – neither overwatering nor underwatering. The usual questions of when to water and how much water to use are influenced by weather, soil type, plant maturity and plant type. Here are some guidelines:
- Overwatering is a frequent mistake of gardeners. It is the number one reason for death of landscaping plants. Overwatering can drown plants by leaving little oxygen for plant roots, which can suffocate and die. Symptoms include wilting, yellowing, leaf drop and twig dieback (these symptoms are not exclusive to overwatering and may be caused by other factors). Excessive watering can also wash away soil and plant nutrients.
- Weather has been a big factor this year. If you receive 1 inch or more of rain during the week, it is unlikely you will have to water. However, you will need to monitor your container plants and newly planted shrubs and flowers, as they may need more water than is available from the rain.
- The amount of watering depends on the type of soil you have. Sandy soils drain more rapidly than clay soils. As a result, sandy soil requires more frequent irrigation.
- Different plants have different watering requirements. Native plants, for example, require little watering once they are established. Some flowers, such as coreopsis and boltonia, tolerate dry soil. Others, such as astilbe and bee balm, like moist soil.
- Be sure to water deeply and thoroughly. Water the base of the plant rather than the foliage, as this will reduce problems with fungal disease. Water the entire root zone and allow the top layer of soil to dry out before the next irrigation. This will encourage deep roots.
- Water in the early morning. This gives the leaves a chance to dry out and is important for disease control.
- Apply water only as fast as the soil can absorb it. Faster watering and sudden deluges of rain can cause erosion or runoff and may not be absorbed into the soil.
FAQ on Watering Lawns and Container Plants
The most frequent questions I get on watering relate to lawns and container plants.
Lawns: How much water does your lawn need? When should you water?
How much water depends on the amount of rain, temperature, soil type and grass height among other factors. A good rule of thumb is 1 inch of water per week. If you get less rain, you can supplement with sprinklers. You can use coffee cans or containers to measure rainfall and supplemental water.
The best time for watering is in the morning between 4 am and 8 am. More of the water is absorbed into the soil because evaporation is low during this time of day. The chance of disease is reduced because the grass has a chance to dry in the morning sun. Overwatering will make your plants susceptible to fungal diseases such as root rot.
Containers: What are some guidelines for watering container plants?
Plants dry out much faster in a container than plants in the ground. I check the moisture in my container plants every day or two. Some of my container plants, such as coleus, need more frequent watering than those which prefer rather dry conditions, such as rosemary and thyme. Many of my plants are in terra cotta containers which dry out quickly and need to be watered more often than those in plastic containers. Water plants thoroughly, until water runs out of the bottom of the pot, whenever the planting material feels dry to the touch. Do not overwater. Morning is the best time for watering.
In recent years, there has been increasing interest in ways to conserve water. What are some of the things we can do to reduce our need for water?
- Good soil preparation, adding organic matter when necessary, will speed up proper plant establishment and enable soil to better hold moisture.
- Select plants that require little irrigation other than during the establishment phase. Drought tolerant or native plants generally have lower water demands.
- Group plants together that need similar amounts of irrigation.
- Mulching helps retain moisture in the soil. Be sure not to mulch up against the trunks of trees and shrubs. Doing so poses a serious risk of disease or insect damage to the plant.
- Use drip irrigation rather than sprinklers to water your plants. By depositing water directly to the soil, drip irrigation helps decrease evaporation and runoff.
- Choose drought-tolerant, low maintenance turf types such as tall fescue or replace areas of lawn with groundcovers.
- Water only when necessary, based on condition of plant. Use hand trowel or soil probe to check for moisture.
To Do List for Early August
- Check the stakes supporting lilies, dahlias, and other tall flowers. Hoop sedum and black-eyed Susan to prevent them from flopping.
- Keep up with the weeds.
- Help contain blackspot on roses by removing fallen leaves and diseased twigs. Avoid wetting foliage.
- Inspect your plants often for signs of insect and disease problems.
- Check the moisture in container grown plants.
- When your basil plants begin to sprout flowers, pinch them off to keep plants producing foliage.
- Evaluate your plant selections and take notes for next year.
- Take time to enjoy your garden!