11 Care Tips For Hydrangeas During a Heat Wave

If your hydrangeas are cooking from the heat this season, you are not alone! The good news is, there's a few actions you can take to keep them thriving. In this article, gardening expert and hydrangea enthusiast Jill Drago walks through her top tips to help your hydrangeas stay alive and look their best during hot summer temperatures.

hydrangeas heat wave

All winter long we look forward to summer. The warm sun, the bright and vibrant flowers fill our frozen minds with hope. With any luck, our hydrangeas are blooming beautifully in shades of blue, pink, white, and purple. Of course, once those heat waves hit in the middle of the summer we are all melting, including our plants!

Hydrangeas are just like most other plants and will struggle in the heat. Even well watered hydrangeas can show signs of heat stress. But do not let that heat stressed hydrangea stress you out too!

So. if you have a heatwave on the way, or if you are in the midst of one right now, read along for some great tips to help your favorite flowering shrub beat the heat!

Step Up Your Watering Routine

Gardener watering plant at base
If you know a heat wave is coming, start increasing your watering frequency before it arrives.

This might seem obvious, but it is the most important thing you can do for your plants during a heatwave. If you know a heatwave is coming it is a great idea to provide your hydrangeas with a deep watering just before the heatwave arrives.

Before you start watering, make sure your hose is empty. If it’s not, let it run for a minute or two to get rid of sitting hot water. Extremely hot water pumping out of a hose is a mistake, and can ruin your plant.

Allow your hose to run at a low pressure and give it enough time to water deeply. I like to rest my hose on the ground and check back every 10 minutes or so. If you have soaker hoses available, this would be a great time to use those.

When you are turning on your hose, be sure to let it run for a few seconds before you begin to water your hydrangea. Water in hoses can heat up to very high temperatures, and can scald the plants and possibly even you.

Remember while watering, aim your hose at the ground. Hydrangeas are known to suffer from fungal diseases. Excess moisture on the leaves will give these diseases more of a chance to spread and cause harm to your already stressed plant.

Attempt to conserve water as well. As we all know, water is a nonrenewable resource that we all need! If you have containers, set them under sprinklers, set buckets under the drip zone of any of your sprinklers and hey, save that water from your kiddie pool. Every drop counts.

Adjust Your Watering Schedule

Watering plants with sprinkler in the evening
When watering in the evening, avoid getting drops on the leaves.

If it is possible for you to water in the early morning or the evening, this is the best time to do so during a heatwave. Water droplets that remain on the leaves can cause burns on the leaves if the sun is allowed to bake them long enough.

Evaporation is also an issue while watering midday during a heatwave. It will be much more efficient for you as well as your hydrangeas if you water them when the sun is not beating down on your gardens.

When you water in the evening, it is more important than ever to avoid watering down the leaves. This is where the fungus risk rises. If you are using an overhead sprinkler or irrigation system, try to water in the morning so the plant has time to dry. 

Provide Some Shade

Blue hydrangea blooms in shade
Most varieties of hydrangea prefer shade during the heat of the day.

Most varieties of hydrangea prefer afternoon shade. If you think your hydrangea can benefit from a break from the sun you can purchase shade cloth online or from your local garden center. But honestly using a beach umbrella or an old bed sheet will work just as well.

Be sure that these fabrics are lighter in color so that they do not absorb too much heat and cook your plants! It is also important not to just lay these shade cloths on top of the plant, you will want to get as much airflow and natural circulation to the plant as you can. Use some stakes, zip ties or twine to create a shade fort for your plants.

Move Your Containers

Gardener moves a container of into the shade
Move containers of hydrangeas to a shady spot.

If you are able to move your containers into the shade, this is the time to do so. Even if it is full shade, this will be a good time to give your plants a break from the heat. Tucking containers into the woods, or along a shady wall of your home would be a great place to keep them cool. Just do not forget to water them!

Planting in lighter-colored pots will help with the heat stress on potted hydrangeas. These wonderful container plants have much less soil around their roots, which means they have access to less water than those in the ground.

If you have containers with saucers, watering from the bottom as well as the top will give your plant extra water. Clumping your hydrangea containers together in a group can take the labor out of this task.

When watering your containers during a heatwave, you may need to pay close attention to how you water them. You will want to water your plant until water comes out of the bottom… and then water some more.

Dried-out soil does not absorb water, as well as moist soil, does, so you will need to give your potted hydrangeas some more water than normal.

Do Not Prune

Pruning shrub in garden
It is not recommended to prune hydrangeas in the heat, as this can stress the plant.

Summertime pruning is not usually recommended. In the event that your heatwave happens to come at the end of the summer or even in the early fall make sure you do not start pruning during this period.

The heat is already causing stress on the plant, and pruning would just increase the negative effects of the stress.

This also goes for deadheading and the removal of any damaged leaves. If your hydrangea has some sunburnt leaves or flowers, they could actually be protecting leaves and flowers that may be hiding underneath them. Wait until the heat passes before trimming away any damaged parts of the plants.

The only exception to this rule would be removing leaves that have fungal diseases or a high population of insects or insect damage. Fungus and insects love stressed plants and will take full advantage of this opportunity causing your hydrangea even more trouble.

Plant Sun-Loving Varieties

Panicle variety blooming in full sun
Paniculata hydrangea prefers to grow in full sun.

I’m looking at you panicle hydrangea growers. These tall, beautiful bloomers do love the sun, and they are also a bit more drought tolerant than other species. This does not mean that they are impervious to the effects of extreme heat. Keep them watered!

Hold Off on New Plants

Gardener planting hortensia shrub in the ground
It is not advisable to plant new plants in the midst of the heat.

This time of the year there are many sales at garden centers on larger plants and shrubs. I love this, and I love to take advantage of these deals. BUT, this is not the time to plant anything new in your gardens.

These plants will likely be deprived of water since they have spent a significant amount of time in a plastic container. Adding them into your garden would definitely be an upgrade for them, but they would continue to struggle.

If you bought some plants but did not get them into the ground before the heat hit, hold off on planting. Keep them well-watered and cool until the temperatures drop.

Do Not Transplant

Woman transplanting shrub
Do not transplant in hot weather, as the plant may suffer from transplantation.

Just as this is not the time to welcome new plants into your garden, this is not the time to move them around either. Hydrangeas are very susceptible to transplant shock, and transplanting in heat.

Transplant shock will look like a very dried-out hydrangea. The leaves and flowers will brown and droop. Transplant shock in cooler temperatures is recoverable, but you may not have the same success in extreme heat.

Pass on Fertilizing

Fertilizer in hand of gardener wearing blue gloves
Fertilizing in hot weather can cause burns to plants.

While in the midst of a heatwave, just let your plants ride it out, don’t try any magic tricks. It may seem like you are giving your hydrangeas a fertilizer that will increase their vigor, however, applying fertilizer will not aid them in recovery from heat stress.

If your plant has been under watered, applying fertilizer can actually damage the plant even further. Fertilizing under these conditions can cause fertilizer burn. This burn can damage the roots, but will show itself as brown and crispy splotches on the leaves.

Watch Diligently For Pests

Japanese beetle on pink hydrangea shrub
Japanese beetles eat hydrangea leaves.

When plants are drought stressed, they become a target for insects.

Spider mites in particular love to feast on a dried out struggling plant, so rude. You will notice these insects by their webbing around the plant. It may look like a spider web that has gone out of control.

Now, I know I have said not to water the hydrangeas by watering their leaves; however, a great and easy way to get rid of spider mites is by hosing your plant down. The spray from the hose will physically knock them off of the plant.

Japanese beetles are also very prevalent in the middle of the summer. I have noticed their population explode in my own garden over the last week or so when the temperatures have really gotten high.

These beetles will munch away on your hydrangea leaves, leaving a lacy look to them. Knocking these beetles off of the plant into a bucket of soapy water is a good way to get rid of the beetles.

Keep Yourself Cool

Gardener spraying pink flowers in garden
Skip taking care of your plants during the hotter parts of the day.

This too shall pass. Plant stress is something that can be resolved with some patience and usually some water. Do not rush out in the middle of the heat to tend to your plants. If you have given them care all season long, you have done enough.

This goes for you too, fellow gardener. Drink lots of water, and do not forget your sunscreen! Try your best to get your gardening tasks out of the way early in the day, or at dusk.

Final Thoughts

Heat waves can be tough on all of us. Luckily they pass with time and we can look forward to cooler weather. Even in the hottest temperatures, there are always things you can do to keep your hydrangeas alive, and thriving. Focus on increasing your water distribution if possible, and leverage containers or shade plants if they are options. With a little additional care, your shrubs should be able to make it through the heat wave and thrive next season.

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