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What do your plants look like in the middle of summer?  Do they thrive despite the hot temperatures?  


Or do they look more like this?

 
Throw in a heatwave, and your lovely, attractive plants may be suddenly struggling to survive.
 
Whether you live in the desert Southwest or more temperate climates, this can happen to you if your garden is not prepared for the heat of summer.
 
So, how do you know if your plants are handling the summer heat?  
 
Take a walk through your garden during the hottest part of the day and look for signs of wilting leaves as well as yellow or browning leaves.  All of these can indicate heat stress.
 
The good news is that you can heatproof your landscape and enjoy a garden filled with attractive plants that thrive despite the hot temperatures that summer dishes out.
 
Here are 5 tips to help you heatproof your garden:
 

#1. Use native or plants adapted to your climate.

 
 
This is perhaps the most important tip for having an attractive, low-maintenance landscape filled with beauty that thrives throughout the entire year.
 
Native (or adapted) plants have unique characteristics that help them to handle the local climate, including the heat of summer AND the cold of winter.
 
All too often, we find ourselves with landscapes filled with plants (often with large leaves) that struggle to survive the hot, summer months.  This results in unattractive plants that we work hard to help sustain them until cooler temperatures arrive.  Usually, these plants are best meant to grow in climates with less extreme heat.
 
Langman’s Sage (Leucophyllum langmaniae)
 
Let’s look at an example of an adaptation that this Langman’s sage has that enables it to handle full sun and 110+ temperatures without undue stress.
 
Notice that the flowers have small hairs.  So do the leaves, giving them a slightly grayish cast.  These tiny hairs help to reflect the sun’s rays, which lowers the temperature of the leaves and flowers.
Mexican Honeysuckle (Justicia spicigera) and Shrubby Germander ‘Azurea’ (Teucrium fruticans ‘Azurea’)
 
Another way that plants have to handle the heat is by having small leaves, which limits the amount of water lost, which helps them to deal with hot, dry temperatures.
 
Here in the desert Southwest, there are many native plants that are used as well as plants from Australia and other arid regions, which have similar climates.
 
To find out what types of plants are best adapted to your area, check your local cooperative extension office for a list of plants.  A visit to your local botanical garden can also be helpful.
 

#2. Provide shade

 
 
Adding shade to the garden can provide relief from the hot sun as well as cooling air temperatures.  The shade benefits plants and can provide cooling to the house as well.
 
*It is important to note that it can be hard to grow many plants in dense shade – especially flowering ones.  However, using trees that provide filtered shade provide just enough shade while allowing enough sun through for plants.
 

#3 Water deeply and infrequently

 
 
Plants need water to survive, and not surprisingly, they need the most in the summer.  However, we often water them too often and shallowly for it to do much good.
 
Shallow watering keeps roots close to the surface of the soil, where the soil temperatures are hot, and the water dries up quickly.
 
Deep watering is the proper method for irrigating plants because encourages deep root growth where the soil is cooler and stays moister for longer.  As a result, you do not need to water as often.
 
“Plants that are watered deeply and infrequently are better able to withstand the heat.”
 
Shrubs should be watered to a depth of 2 feet and perennials and groundcovers to 18 inches.  You can determine how deeply you are watering by inserting a piece of rebar down into the soil (right after you have finished watering) to see how long you need to irrigate.  On average, 2 hours is the length of time to irrigate to the desired depth.  
 
Almost as important as watering deeply is the time of day that you water. The best time to water is early in the morning.  Watering plants in the afternoon is not as useful since plants allocate their resources at that time toward surviving the stresses of the heat and so they do not take up water as efficiently.  
 
Click here for watering guidelines for the Phoenix metro area.
 

#4 Mulch around your plants

 
 
Not surprisingly, mulch has a variety of benefits and not just in regards to heat proofing your garden.
 
Mulch serves to help cool soil temperatures in summer while helping to conserve moisture – all important in helping plants thrive despite hot temperatures.
 
A bonus is that they also help to prevent weeds from taking root.
 
 
Let’s take a minute to rethink our definition of what makes an excellent mulch.  
 
While shredded bark and wood chips may come to mind, did you know that fallen leaves, pine needles and even fallen flowers can also serve as a mulch?  That is how nature does it.
 
So, the next time you are tempted to whip out your leaf blower, how about directing it toward the base of your plants where the leaves and flowers can serve as a mulch?  They will also help to improve the soil around your plants as they decay.
 

#5 Ditch flowers in favor of succulents in containers

 
While growing pretty flowers in containers are relatively simple in fall, winter and spring-summer can be another matter entirely.  Often, it can be hard to grow flowering annuals in pots throughout the hot summer.
 
The reasons for this is that the soil around the roots of container plants is hotter than if grown in the ground.  This is especially true for the outer 6 inches of soil which heats up in response to air temperatures and the hot container.  As a result, annuals can wilt and struggle to produce flowers in summer.
 
Succulents are a great way to enjoy attractive container plantings throughout the year, not just in summer.  Their ability to store water is what makes them an excellent choice for containers.
 
 
If you want to grow something else besides succulents, how about trying heat-tolerant shrubs? Bougainvillea does great in pots as does lantana.
 
 
Another tip for containers is to leave them empty in the summer months and wait until fall to plant them.  
 
When thinking in terms of growing plants in containers in hot climates, bigger is better – at least 2 feet wide at the top.  The larger the pot, the more soil and therefore, more insulation for the roots from the hot outer zone.
 
 
**So what can you do if you do have plants that are struggling in the heat – particularly during a heatwave?  Other than replacing them, you can provide them with temporary shade such as a patio chair strategically placed so that it protects it against the afternoon sun.  A light spraying of water over the plant and surrounding area in the evening can help reduce the temperature – don’t do this when the sun is out, or you may burn the foliage.

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Forecasts of a heatwave in the desert may seem a rather foreign concept when temperatures in summer are routinely over 100 degrees.  However,  when temps are predicted to be 110 degrees and over, plants in landscapes that normally handle hot weather without complaint, can suffer. 

The best preparation for heat-proofing your landscape begins before summer.  However, with the imminent arrival of a heatwave, here are two tips that will help your plants survive.
 
 
1. Provide extra water by irrigating shrubs and groundcovers in the early morning hours for an extra 1/2 hour when temperatures are forecast over 115 degrees.
Plants can uptake water more easily in the early morning as opposed to being watered during the day.  During the heat of the day, plants have to devote much of their resources to handle the stress of the heat and cannot uptake water efficiently.  Therefore, it’s best to water early in the morning so that they are replenished with water and ready to face the excessive evaporation that will occur with temperatures over 115 degrees.  
*It’s important not to overwater plants, so if the heatwave lasts more than three days, skip a day between providing extra water.
 
2. Provide temporary shade for heat susceptible plants such as hibiscus or roses.
The sun’s intense rays are even more focused during a heatwave and can cause stress to the plant itself, including sunburn damage.  This is especially true for plants that receive hot, western sun or in areas that receive reflected heat.
 
For shrubs and groundcovers, leaves may wilt and turn brown in response to a heatwave.  Even cactus and other succulents can suffer sunburn or other heat stress, which often reveals itself as yellowing.
 
Temporary shade can be provided using sections of shade cloth.
 
 
In a pinch, a lawn chair can work to add a welcome spot of shade for a plant.
 
Old sheets tied to posts, chairs or trees can also provide temporary shading until the heatwave subsides.
 
 
As I mentioned earlier, the best way to handle a desert heatwave is wise planning including using native plants, mulch and the use of trees to provide shade.  
 
In the meantime, escape the heat by hibernating indoors as much as possible 🙂
 
**You can read more about how to create a heat-proof garden in an earlier blog post.