When a heatwave is on the horizon, it’s important to do some prep work in the garden to help your plants survive and thrive. The most important steps include deeply watering plants, providing protection from the sun, and mulching to keep soil and roots hydrated.

Established and mature plantings tend to fare better in extreme heat. However, new or tender plantings in your garden may need some extra attention and preparation. Here are some guidelines to give your garden the best chance at surviving the summer heat.

How to Set Up New Plants for Success

New plantings are most vulnerable to extreme weather conditions. It takes about three years for new plants to develop extensive, healthy roots and to be considered “established.” If drought tolerance is indicated, it will only be so once the plant is established.

Here are some helpful planting tips and best practices for getting new plants off to the right start:

  • Amend poor soil when necessary and plant at optimal times of the year (Spring and Fall).
  • Before planting, pre-soak dry or root-bound plants in water, root stimulator, or compost tea; loosen up compacted roots.
  • Dig a hole in the ground twice as wide as the plant root ball, but no deeper. Fill the hole with water to ensure proper drainage and pre-moisten the planting area.
  • Plant at proper level in the soil and water the plant again after covering roots with soil.
  • Apply 1-3 inches of mulch to cover the root zone; avoid piling mulch around stem or crown of plant; provide about 4 inches of clearance from the plant before mulch layer begins.

After your plants are in the ground, perform a quick audit of your water source to see if watering frequency or duration should be tweaked:

  • Dig into the soil after watering to see how deep the moisture has penetrated and to determine ideal duration of watering time.
  • Test coverage/volume of sprinklers by distributing shallow, open containers (e.g. tuna cans) around the lawn before running sprinklers, then measure the amount of water in your containers after a set amount of time. The average lawn requires 1-2 inches of water per week to stay green.
  • Although drip irrigation can provide deep watering, most sprinklers only wet a shallow layer of soil and are not enough for establishing new plants.


How to Prepare Your Garden for a Heatwave

1. Water Deeply

Water plants deeply in the morning or evening when evaporation is limited. This means giving them a good soak so that water penetrates through the top few inches of soil and the roots are saturated. A garden hose is the most fool-proof tool for this as many sprinklers only saturate the top inch or two of soil. Check plants frequently, as the soil will dry out much faster than usual in a heatwave and you may need to water every day.

Always be aware of your specific plant’s needs—some plants like Ceanothus, Cistus, or Manzanita don’t need much summer water, while others like Hydrangea may wilt even when properly watered.

Potted plants, like container gardens or hanging baskets, will dry out much faster than those in the ground and will likely need to be watered once or twice per day. If possible, move them into shady areas. All that water also flushes out nutrients in the soil, so it’s a good idea to carefully add fertilizer after the heatwave has passed. Read our blog to learn all about watering and heat recovery.

2. Apply Mulch

Mulch is typically composed of shredded organic matter like leaves or bark dust. Apply 1-3 inches of mulch on top of the soil to cover the plant’s root zone, without piling it up around the stem. Mulch provides a protective layer, helping to keep the soil moist and plants hydrated during heatwaves. It also serves as a kind of blanket for roots in the winter, keeping the roots from freezing underground. We recommend mulching at least once per year, and you can learn more in our blog The Whys and Hows of Mulch.

3. Use Protection

Give your plants a break from direct sun by using shade cloth. This porous material blocks 50% of UV rays and should last for many years. Consider building a basic structure and stretching the cloth over the top, like an umbrella, to protect your plants from the hot sun.

Products known as anti-transpirants may also be applied to certain plants to reduce moisture loss from the leaf surface. We carry a product called Wilt-Pruf for this purpose.

And just in case your plants bore the brunt of the heatwave, check out our Q&A on extreme heat recovery for your garden, or stop by to speak to one of our gardening experts!

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