How to Water Your Garden in a Heatwave – And What Not to Do to Save Your Plants
Keep your plants healthy even when temperatures spike
Heatwaves are becoming more common, making it crucial to understand the intricacies of watering plants in hot weather. Get it right, and your plants can thrive even in soaring temperatures. But get it wrong, however, and plants will struggle and potentially die in dry soil.
Best practise is to water early in the morning, water deeply, mulch to retain moisture in the soil, and keep a closer eye on pots that can dry out in the blink of an eye. What you shouldn’t do is water at the hottest time of the day and just give a light sprinkling, which does your plants no good.
Here we look at when to water a garden during periods of extreme heat and how to gauge the right amount of moisture to give them. These two factors are always integral to how your garden copes in a heatwave. As our summers get hotter, the following factors will make a big difference to your plants.
A classic metal watering can, like this one at Walmart, is a proven go-to watering tool for vegetable gardens, flower containers, or balcony planters.
Do Water Early in the Morning
Watering plants at sunset when it's cooler is a good alternative to watering in the morning
During hot weather, you want to ensure that whatever watering you do is efficient and the most water possible is available to the plants. The simplest and most effective way to ensure that is to water at the best time of the day.
If you water in the morning or late in the evening, you prevent the rapid evaporation of water that occurs through watering in the height of the sun. The temperature is also cooler at that time of day, and your plants are in the best condition to absorb any moisture in the soil.
Watering the plants early in the day, in particular, can help set them up ready to face the hotter weather that’ll arrive in the upcoming hours.
While first thing in the morning is best, watering in the evening is also a good option, though it can bring additional risk as foliage sits damp overnight, which can attract fungal diseases.
By watering in the morning, you allow foliage to dry out completely during the day, which significantly reduces the risk of fungal diseases. A programmable timer like this on Amazon can be used to schedule your automatic irrigation for the morning.
Don't Water Plants at the Peak of the Day
Full sun can result in lots of water being lost to evaporation
If you water during the peak midday sun, during the hottest part of the day, it offers no benefits to you or your plants. Not only are you subjecting yourself to the worst of the sun and potentially having to manhandle heavy watering cans in the heat, but it does no good to your plants and can even scar them.
Sean Lade, irrigation expert and director of Easy Garden Irrigation, stresses that gardeners need to ‘avoid watering in the heat of the day’. He adds: ‘Watering at midday when the sun is at its peak can lead to rapid evaporation, reducing the amount of water that reaches the roots.
‘Also, water droplets on the leaves can act as tiny magnifying glasses, which can lead to leaf scorch.’
To avoid leaf scorch, always water the base of the plants. Aim the watering can or hose at the bottom of the plants rather than watering the foliage. Not only can soaking the leaves lead to leaf scorch, but it can also make the plants more susceptible to fungal diseases, such as powdery mildew.
A watering wand can be attached to a garden hose to easily direct water at the base of plants, while it can also reach hard-to-reach areas and hanging baskets. An example of such a wand is this telescopic watering wand, available at Amazon.
Do Water Deeply
Plants always benefit from being given a good, deep watering
Plants always benefit more from deep watering than lighter, more frequent irrigation. This is definitely the case when watering plants in hot weather, but also an important point to remember whenever you are out watering.
By watering plants deeply, you encourage them to grow stronger, deeper roots. This makes the plants more resilient to dry conditions as those roots can seek out any moisture deeper in the soil.
Watering deeply also increases the likelihood that the water reaches the root zone, where your plants need it most. This is better than the water simply sitting on the surface and disappearing to evaporation once the temperatures rise.
A soaker hose is a great watering tool for steadily applying water directly to the soil, and you can get a 25-foot soaker hose at Walmart that will slowly release water to the roots.
Don't Just Water the Surface
Just lightly watering plants leaves them at risk in hot weather
If you just water the surface, then it can cause multiple issues for plants. One is that the water you are applying will not adequately hydrate the roots, leaving them unable to tolerate increased temperatures.
Mark Lane, award-winning garden designer, author, and TV presenter, recommends not to ‘water a little at a time’ or you will likely see the consequences of that when a heatwave strikes.
He adds: ‘It is better for the plant to water well and deeply. Keeping the soil moist will prevent heat stress, which can be seen by wilting foliage. If soil dries out and water is lost, the condition of the plants will worsen, turning them brown and crunchy.’
Plants given lighter sprinkles of moisture will have smaller root systems, making them more at risk when the top inch or so of soil dries out during a heatwave. It also makes the plant more prone to being topped and roots snapping in strong winds.
Mark Lane is a multi-award-winning landscape designer with over 20 years of experience. He is also a regular TV and radio broadcaster and a published garden writer.
Do Mulch to Retain Moisture
Mulch can retain water and keep roots cool in hot weather
Mulching helps to retain water in the soil for longer and makes it available to plants. It can be invaluable to keep soil moist in summer when plants are likely to be extra thirsty.
Michael O’Brien, a garden designer in Los Angeles, California, recommends: ‘Apply organic mulch around your plants to help retain moisture in the soil. Mulch acts as a protective barrier, preventing excessive evaporation and keeping the soil temperature more stable.’
By mulching, you are offering many benefits to your plants during a heatwave. You are conserving moisture and reducing evaporation, but also keeping the soil cooler, which protects the plants from heat stress.
Mulching also suppresses weeds, which prevents them from competing with your garden plants for water. It means the water you are applying in summer exclusively benefits those plants, rather than being stolen by unwanted weeds.
Put a layer 2-4 inches deep of organic types of mulch, such as compost, wood chips (like this Miracle-Gro all-natural mulch from The Home Depot), or straw, around plants. A bonus is that the mulch will also add nutrients to the soil as it breaks down.
Michael O'Brien is a certified organic gardener who designs and maintains edible gardens for clients around Los Angeles. He also runs a coaching program to help people efficiently use their space and maximize their harvests.
Don't Unnecessarily Overwater
Overwatering can stress plants and wash off the top layer of soil protecting the roots
Overwatering can be as bad as underwatering; both are common garden watering mistakes capable of killing plants. It can often be a case of overcompensating in hot weather, unwittingly thinking your plants need extra water due to the heat.
However, overwatering leads to root rot and other issues. Putting excess moisture in the soil, more than plants need, causes stunted growth and stressed plants that are more susceptible to pests and fungal diseases.
Always check the soil’s moisture level before watering. A good way to check, especially when watering plants in containers, is to use your fingers to check the moisture levels a few inches under the surface.
Or use a moisture meter to check at a depth in the soil. If the soil is still damp, then wait another day or two before watering. A meter such as the XLUX Soil Moisture Meter, available at Amazon, can help you get instant results in the ground or in containers.
Do Check Pots Regularly
Pots can dry out very quickly in hot weather so may need multiple waterings a day
‘Most importantly, don’t forget about your potted outdoor plants. They require more water than the plants in the ground,’ warns Michael O’Brien. ‘Ensure your containers have proper drainage holes and monitor their moisture levels more frequently. Adjust the watering frequency to prevent the soil from completely drying out.’
When temperatures spike, plants in container gardens suffer more quickly than those in flower beds or borders. The deep soil of borders, or even raised beds, can hold moisture deeper down; however, in pots there is a finite amount of soil and moisture.
Moisture can be depleted quickly during a heatwave, leaving plants at risk of heat stress and wilting. Careful, regular observation is recommended during hot weather.
Jason Wilkinson, founder of Qwickhose, recommends: ‘For any plants in containers, it’s also better to water these twice daily to ensure they are getting enough moisture, as soil dries out much quicker in pots.'
Make sure to give pots a good soak as underwatering is a common container gardening mistake. The best approach is to thoroughly soak the root ball until water runs out of the pot's drainage holes.
Don't Forget to Move Pots
Move pots to a shadier spot during a heatwave to stop them from quickly drying out
One of the simplest things to do with plants in containers is to move them to a shadier spot ahead of a heatwave. Moving those pots out of direct sunlight and into garden shade can reduce their heat exposure.
Keeping containers in full sun is a common mistake gardeners make during a heatwave, and it can kill plants. The pots themselves can get incredibly hot, especially black planters. That causes problems for the plants in them as their roots bake.
Mark Lane warns that, as extreme temperatures can ‘cause heat stress, stunt growth and premature death’, it makes it important that heat-sensitive plants are protected from excessive sun.
He also recommends ‘position all plants in a shadier spot when watering’ to ensure they take in all of the moisture given to them.
When it comes to indoor plants and hot weather, he adds: ‘Try and keep the air cool by providing good airflow. Open windows and doors. This will also help keep down pests and diseases and will allow water to be soaked up by the soil more readily and evenly.’
If you are thinking of how to water plants in pots while on vacation, you can consider an automatic watering system, such as this drip irrigation kit available at Walmart, that can provide drip irrigation for potted plants.
Shop Our Watering Edit
This 100-ft stainless steel garden hose is flexible and kink-free, and it resists punctures. It comes with a multi-function nozzle with 10 settings.
This flexible garden hose expands to 50 feet with water flow and is kink- and tangle-resistant. It has an on/off valve and solid metal fittings for a long lifespan.
A metal sprayer nozzle that offers seven different water patterns for convenience. Easily switch between a center, flat, cone, angle, shower, mist, and jet setting.
A soaker hose made from 65% recycled material that comes with two male connectors with caps and two female connectors for hooking it up in the garden.
A rustic watering can made of heavy-gauge metal with a capacity of 0.8 gallons (3 liters) of water. It has a fine rose attachment for watering delicate plants.
A drip irrigation system with quick-connect fittings for easy installation. It includes 230 ft of high-quality tubing (1/4” & 5/16”) and adjustable drip emitters.
It is important to remember that not all plants need lots of extra water during a heatwave. Some native and drought-tolerant plants are more accustomed to local temperature fluctuations in summer, but not all plants are so amenable.
To help you spot any strugglers in your yard, our guide to plants that need more water in a heatwave features seven types of plants that will need extra focus when the temperatures rise in summer.
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