Watering During a Heatwave

1. Watering deeply BEFORE high temperatures arrive is ideal.
2. For most plants, watering in the morning or evening is best.
3. Getting water on leaves will not cause burning. It can abate fungal diseases in some plants, such as roses and squash, so watering most plants in the morning is ideal..
4. Adding a layer of mulch to soil surfaces will help to maintain moisture in the soil.
5. Moving some plants into shady areas or setting up shade cloth for the duration of the heatwave can help.

Newly installed plants are among the highest priorities for watering during a heatwave. These plants have not rooted into the ground completely, and are at a greater risk of drying out during times of excessive heat. Water new plantings deeply—using soaker hoses, drip systems, or sprinklers.

Deep watering entails watering at a slow pace that allows the water to soak deep into the soil, reaching the roots. Often, this means watering for 30-60 minutes at a time, 2-3 times each week, until plants are established. When temperatures normalize, continue with deep watering, but back off to 1-2 times each week.

Tree bags are fine to be used for newly planted trees, but only for short periods of time. They should be removed between waterings to avoid causing rot at the base of the tree’s trunk. Tree bags are not effective for watering established trees, as the roots of a mature tree extend far beyond the trunk.

Shading newly planted areas with umbrellas or shade cloth can really help to reduce heat stress.

Plants in containers dry out faster than plants that are growing in the ground. During a heatwave, they may need watering more than once each day.

When you know an extreme hot spell is coming, it can help to move smaller containers into shaded areas for the duration of the hot weather event. Hanging baskets can be helped by placing them on the ground.

Containers and hanging baskets with annuals lose a lot of their nutrients when they’re watered this often, so it’s a good idea to fertilize after the heatwave is over.

Even the most established plants in our gardens appreciate a deep soaking a few times during summer, and fortifying them with a long slow watering before a heatwave is a good idea. It’s important to apply water to the whole root zone, which reaches at least to the dripline of the plant.

Use a soaker hose or sprinkler for 30-60 minutes at a time. During normal summer temperatures, this type of watering can happen every 2-3 weeks. In times of extreme heat, 1-2 times each week may be necessary.

Know your plants though! Some plants prefer almost zero water during summer (e.g. manzanita, Ceanothus, madrone, and cistus) and others wilt even when they have ample water (e.g. Hydrangea and Rhododendron). So adjust watering accordingly.

Vegetables and fruits that are developing fruit during a heat spell need regular watering to ensure good production. Typically, vegetables will require daily watering during summer weather, but may need a second watering when temperatures are extremely high.

Lettuces and other leafy crops can be kept from bolting (going to seed) by misting or watering their leaves in the afternoon.

Tomatoes prefer even and consistent watering to help curb Blossom End Rot. Adding lime to the soil when planting, and spraying with Fertilome Yield Booster, can help to correct calcium deficiency and prevent Blossom End Rot. Sprays should only be applied when temperatures have dropped below 85°F.

Soaker hoses are a great way to deliver water at a slow pace, allowing it to sink deep into the soil where roots are located. It can take time for water to seep in, so soaker hoses should be turned on for at least 30 minutes at a time.

• Work best on even ground.
• Should be no longer than 100 feet to be effective.
• They operate well when water pressure is lower, so don’t crank the faucet up too high.
• Hoses should be placed in such a way that water reaches the entire root zone.

Shade cloth can help keep the air temperature down and reduce transpiration is a great idea. It’s often only needed during the duration of the heat spell and can be removed when temperatures normalize. It’s very helpful to use when shade-preferring plants are accidentally planted in sunny sites. The shade cloth that we carry will block 70% of sunlight. We offer several colors, and they are all equally effective (the color choice is completely aesthetic).

Drip irrigation is an excellent way to keep your plants happy and healthy throughout the growing season. They’ll even save you time and water.

If you want to give plants a bit of TLC after a heatwave passes, applying Maxicrop to the leaves is a good idea. It provides a light blend of nutrients and trace minerals that will provide a bit of nutrition while plants recover.