Beating the Heat in the Garden

So, did you ever imagine you'd be trying to cultivate your garden in an oven this season? It's hot -- the hottest summer in the U.S. since they started keeping records. It's so hot . . . well, I'm sure you've heard the punch line -- or have one from your own somewhat sweaty recent gardening experiences.

I have to confess that I'm surprised and a little anxious. It's hard to pamper plants through this kind of extreme weather. Sometimes twice daily watering won't even do it. My dill and cilantro bolted months ago after an indecently brief stint in the herb patch. It's been downhill from there, I'm afraid. Even the insects I encounter seem sluggish and frankly reluctant to spend any more time tending to business than they absolutely have to. You know when the enemy gives up too easily that something is really amiss.

I haven't lost many plants, thank goodness, but I can almost hear the stressed little whimpers floating my way from the vegetable garden. Let's hope this is a one season wonder and we'll be back to normal -- if there is a normal for the garden -- next year. In the meantime, here are a few tips for handling the next heatwave:

Mulch - Putting down a layer of mulch now will help keep moisture in your soil from evaporating as quickly as it would otherwise. That means more moisture available to your plants during the hottest part of the day. You can mulch your potted plants, too.

Water granules - These tiny beads (not to be confused with the larger beads found in flower arrangements) absorb water and hold it longer than the surrounding soil. That means the water you do make available to your plants will stick around -- hopefully long enough to do some good. Water granules can be added to an existing flowerbed with a little minor excavation. They are a granular polymer product that absorbs excess moisture in the soil and holds it like a water reservoir that plant roots can tap as needed.  They remain active in soil for up to five years and some marketing materials suggest they can reduce the amount you may have to water by about 50 percent. Water granules are considered benign.

I've seen granules about the size of a grain of sand expand to pea size.  The only real negative I've read of -- and I haven't experienced it myself -- is that roots will tend to gather where the granules are concentrated and not distribute themselves as they would normally -- or go deep into the soil for moisture. Water granules are added to some "water retentive" potting soil mixes, so remember this useful little item for next year.

Shade netting - Garden fabric and row covers help keep plants warmer in spring, but a similar material can also keep them a few degrees cooler in the summer. Shade netting can reduce summer sunlight by 50 percent while still allowing good air circulation to your plants. It will also help retain moisture. The material itself is typically UV enhanced polyethylene. All you do is place a series of hoops over your flowerbed, drape the fabric over the hoops and use clothespins to fasten the fabric in place. If you're gentle, you can use the fabric year after year.

Create a Windbreak - A stiff breeze can suck moisture right out of your plants.  Fences and movable barriers on the windward side of your herb or vegetable patch (or flower border) can help plants retain moisture and survive protracted drought conditions.

Reservoirs - For those potted plants on your patio, you can purchase self-watering pots, but if you didn't have the forethought to overhaul all your established pots for this season's challenging weather, try putting together a makeshift water reservoir using a soda bottle and a sponge. You can find my past post on how to make this work here: Watering Plants on Hot Summer Days.

Sponges - Another option is to outfit potted patio plants with household sponges.  The idea here is that the sponge will hold water longer than the soil and provide an emergency water reservoir for hot days.  Just place a sponge or two in the bottom quarter of the pot and fill the rest with soil as you would normally. I place mine just over a layer of coarse gravel, broken crockery or other well draining filler.

Special Tips Beating the Heat in the Garden

I don't know what the next month or two will have in store, but these tips will help you deal with stressed plants and the potential discouragement of heat related plant losses:

  • Avoid fertilizing your plants until the weather cools down a bit. The added stress can cause problems, and all that extra growth will just need water you may not be able to supply.
  • Water plants deeply. Brief surface watering encourages plants to relocate their roots closer to surface of the soil. You want your plants' roots to go deep down where there's likely to be (consistently) more moisture. Give this a try, especially with plants like tomatoes that can have problems with splitting skins from inconsistent watering.
  • Avoid watering at sunset. When temperatures start to cool down, wet plants are more susceptible to fungus and mildew. These unsightly conditions may not kill your plants outright, but they can weaken them and make them more vulnerable to predation by insects and the vagaries of the weather. If you must water at night, use a drip system or keep the hose on the ground.
  • Buy the right mulch. Most mulch products have advantages and disadvantages. Rocky mulch is pretty indestructible, but it can actually make your soil hotter -- not a good thing these days. Wood based mulches applied next to your home's foundation can put your home at greater risk for a termite infestation, too. Don't just grab what's on sale and hope for the best. Discuss mulch products with the folks at your local nursery or with your regional Cooperative Extension Office. The right mulch can protect your plants, retain the nitrogen balance in your soil and help improve your soil over time.


Chenault, Jerry A. "Maintaining Gardens in Summer Heat & Droughts."

Cornell University. "Cornell Gardening Resources: Microclimates." 10/8/10.

Melancon, Merritt. "Like people, plants sometimes need a break from the summer's heat." University of Georgia. 7/5/12.


  1. So what're the chemicals in water granules? Do they down and leach into the soil over time? How do they affect the organisms in the soil?

  2. I live in the tropics where its always like the temps you guys have these days. We have a technique here that is used. Its a thick black garden plastic that is spread over the soil. Holes are cut out for the plants. This keeps the moisture from escaping too quickly. It also keeps weeds at bay and eases the maintainance in the garden.

  3. I need to know what to do with them in the winter I want to bring them inside but will a flourecent light be strong enough to keep them alive in a big pot?

    1. Hi Kellso,

      This older post about bringing herbs indoors should help:

      Good luck,


  4. Our beetles love the mint, but won't touch the Rosemary. I'm going to try sprinkling some of that magic.


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