Gardening in a heat wave: five ways to nurture plants in hot weather

Growing food gives us a front-row seat to changes in climate and weather. When gardening in a heat wave, we need to keep our plants irrigated. Here's how.
During the heat of summer learning to water smart is a must.

Gardening gives us a front-row seat to changes in our climate and weather. Plants are incredibly sensitive to variations in temperature and daylight, and by observing them closely, we can get cues about our surroundings that would otherwise fall below human perception. The timing of opening flowers, ripening fruit, pest invasions and germinating seeds tell us a story.
In 2015 in Vancouver, many crops have developed two to three weeks ahead of schedule. Berries have ripened early. In my garden, sun-loving basil was once barely worth growing — now it’s taking over one of my beds. Meanwhile, spinach, a cool weather crop, used to be the easiest thing for me to grow. Now, I’ve given up on it entirely due to heat-induced poor germination.

Although it’s just the beginning of the official summer season, we’ve already experienced temperatures of over 30 degrees celsius. As a born-and-raised Vancouverite, this weather seems quite different from my memories of a typical local summer. Last year came close, but 2015 brings an intensity unlike anything I’ve experienced. May 2015 was a record dry month for Vancouver. Remember when summer was a non-event here, with clouds and even occasional rain?

In a warming climate, gardeners are uniquely positioned to take note of changes in our environment. Gardening gives us an intimacy with the land that no other activity offers. We spend time in our garden day after day, year after year, and continually adapt to what the weather offers to us. We are the first people to notice some of the changes that happen in our climate. For this reason, I believe that gardening can potentially be not just a hobby and a way to supplement our grocery shopping, but a form of citizen science that gives us important information about our surroundings.

The City of Vancouver has issued Stage 2 watering restrictions for our current dry spell. At the moment, the restrictions do not extend to vegetable gardens, but if reservoirs cannot keep up with demand, watering bans could potentially increase in scope. Along with a lack of precipitation, our growing local population is a major factor.

In this hot weather, our plants need regular watering. We also need to take extra precautions to avoid wasting water. Here are my top recommendations for gardening in a heat wave:

1. WATER EARLY IN THE MORNING
Plants can most efficiently absorb water in the relatively cool early hours. If you water your plants in the heat of the day, much of it will evaporate before it gets into the root system — or, worse, cause damage to leaves, with droplets of water acting like magnifying glasses that concentrate heat. Watering in the evening is your second-best choice, but keep in mind that residential water use is higher at this time (think cooking and showers), leading to greater risk of overuse. Evening watering can also cause moisture to sit on leaves overnight, increasing the risk of certain plant diseases.

2. CONSIDER INSTALLING A DRIP IRRIGATION SYSTEM
Irrigation systems can save a ton of water, and perhaps even more importantly, your time. The small upfront expense can be truly worth it, especially if you plan to keep your garden going for years to come.

3, WATER DEEPLY AND IRREGULARLY
Watering too frequently, and too lightly, is a common gardening mistake. Instead, try watering deeply and irregularly once your plants are established. Big crops, like tomatoes, kale, potatoes and squash, only need daily watering if they’re in pots. If you’re using raised beds, try giving them a good soak every second or third day. In addition to saving water, this will encourage your plants to develop stronger, deeper root systems. Small greens like lettuce, and areas with newly planted seeds or transplants, still need daily water.

4. HARVEST AND COOK SMART
Stay on top of your harvesting, especially with leafy greens. If your arugula is looking perfect, now’s the time to pick it. If you wait too long, it will start to bolt (go to flower). Big leaves on plants require a lot of water to stay healthy and wilt more quickly than smaller leaves.

When harvesting, take your salad spinner out into the field, and pour the washing water back into your beds. If you’re blanching vegetables for winter eating, try cooling your pots of nutrient-rich blanching water overnight, and pouring it into the garden in the morning. Every little bit helps.

5. USE MULCH, AND TRY GROWING PERENNIALS
For bigger crops like kale and garlic, apply mulch — a layer of straw, leaves, compost or other organic material — around the roots to reduce evaporation. Mulching can greatly decrease your plants’ need for water.
Add perennial herbs, like sage, chives, fennel, thyme, mint, lavender and oregano to your garden. These plants are incredibly productive, attract beneficial insects, and need very little water once established.

Growing food gives us a front-row seat to changes in climate and weather. When gardening in a heat wave, we need to keep our plants irrigated. Here's how.
Applying mulch to your plants can greatly decrease your plants’ need for water.
Growing food gives us a front-row seat to changes in climate and weather. When gardening in a heat wave, we need to keep our plants irrigated. Here's how.

3 Responses to Gardening in a heat wave: five ways to nurture plants in hot weather

  1. thank you . I’d read an inch a week, but in this heat and drought, that doesn’t seem to be enough. ps What to say to God and Mother Nature when it rains in the evening /and or nights? I’ve always wondered about that

    • Hi Cait – yes, when the heat gets to a certain point, you’ll need to water more often, even once or twice a day. When it rains in the evenings, temperatures tend to be a bit cooler altogether, so you won’t have the same problems as with watering mid-day. Happy gardening!

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