Your Yard & Summer Heat Stress

Summer heat waves can be uncomfortable for everyone – even your plants! Extreme heat (often defined as sustained temperatures of 90 degrees or more) can cause slowed plant growth, wilting, decreased fruit production or worse!

How is heat stressful for plants?

Water is moved through plants and into the atmosphere through a process called transpiration. On hot days, transpiration rates increase and plants lose water faster as it evaporates off the leaves. This water loss creates wilting and can also cause damage to plant tissue.

Heat stress can also severely hinder photosynthesis (the process by which plants produce energy) and deplete a plant’s food reserves. And when plants are weakened by heat stress, they are a lot more susceptible to pests and diseases.

Watering during heatwaves

How often should you water? Watering the right amount becomes especially critical to minimize plant stress. When daytime temperatures rise above 90 degrees Fahrenheit, it’s a good idea to water daily or at least every other day so plants can continue cooling themselves through transpiration.

Plants that have a deeper root system (those that have been established in your landscape for several weeks or more) could have their needs met by watering every other day during a heatwave. But plants that are newly established (like sprouts or recently planted seedlings with shallow root structures) could benefit from daily watering (or evening watering multiple times a day). Installing an underground watering device like Root Quencher could help newly established plants grow deeper root structures.

If you’re watering with Rachio Smart Hose Timers or Sprinkler Controllers, your watering schedules automatically adjust according to the weather. But in cases of extreme heat, it’s a good idea to pay attention to your plants. If you’re noticing wilting or other signs of heat stress, you can use Quick Run to give your plants a hydration boost.

When should you water?

During a heat wave, you should water early in the day (ideally in early morning, before heat from the sun increases water evaporation from the soil). Water close to the plant using drip irrigation, a soaker hose with a smart hose timer, or even water by hand to make sure water is reaching the roots.

Which plants are most at risk?

Plants vary widely in their ability to tolerate heat.

Generally speaking, cold-hardy plants (like kale, broccoli, garlic, spinach and others) which thrive in cooler weather will suffer more during warm weather. These typically cool season plants are particularly at risk during extreme heat.

Heat-tolerant plants like peppers, tomatoes, corn, and okra will fare better in a heat wave, but even they have limits on how much heat they can withstand, and for how long.

Even if plants can withstand long temperatures and continue living through the heat, they may not be able to produce fruit as expected. For example, in sustained daytime temperatures of more than 90 degrees Fahrenheit, tomatoes often stop setting fruit (meaning tomatoes have a harder time “setting fruit”, or developing from tomato flower to tomato fruit). This results in lower fruit yields/fewer tomatoes.

Other tips for managing heat stress

If you’re watering using a sprinkler system, make sure all of your sprinkler valves are working as expected; malfunctioning sprinkler heads might not be able to deliver the water plants need to survive the heat, so it’s critical that you rule out any sprinkler issues if you’re depending on your system to water automatically.

If you have a Rachio Smart Sprinkler Controller, you can use the Valve Monitoring feature to automatically monitor the health of your sprinkler system and alert you to major watering issues that could cause plant death during a heat wave.

It’s also a good idea to install water efficient sprinkler nozzles (Hunter and K-Rain are Rachio recommended, as they both give more uniform watering coverage and avoid excess water evaporation).

Potted plants

Remember that potted plants can be particularly susceptible to overheating, as containers dry out quicker than in-ground plantings. Pay special attention to these areas of your yard during high temperatures and frequently check moisture levels to make sure the soil isn’t completely dry.

If you want a hands-free way to keep potted plants hydrated, you can program a Smart Hose Timer to water for you!

Traveling

Smart sprinkler controllers and the automatic features included with them can help you water more efficiently and make the most of every watering. If you’re traveling or away from home during a heat wave and want to ensure your plants are being watered the right amount, you can use a smart hose timer paired with a hose to automatically water (no sprinkler system required!).