Our climate is changing fast, and gardening through a heatwave is quickly becoming a normal part of the Hamilton growing season rather than a once-a-summer surprise. We've watched our hardiness zone shift in just the past few years, and the city's own climate projections expect our number of days over 30 degrees to more than double within a generation, from about 16 a year historically to closer to 37. Long stretches of extreme heat aren't the anomaly anymore. They're the forecast.
If this is your first season and you've never done this before, you haven't fallen behind on anything. When it comes to new territory, no one's an expert. We're just building the confidence to tackle these conditions together. The truth is that a garden set up thoughtfully, plus a clear sense of what to prioritize when things get intense, is most of the battle. Get those two things in place and you'll know that both you and your garden can ride these stretches out. Let's walk through it.
Watering your garden through a heatwave
The clock matters less than the temperature. What you're really after is the coolest stretch of the day, when the soil isn't already baking and water has time to soak down before the sun pulls it back out. In a normal summer that's roughly before 9am. In a week like this one, when it's already 28 degrees by 9, that window has shifted earlier. You're looking at dawn, or close to it. The lowest temperature of the day lands right around sunrise, so the earlier you can get out there, the more of that water reaches the roots instead of evaporating off the top.
If dawn isn't happening, no judgment, evening is your fallback. Wait until the sun is off the beds and the worst of the heat has broken, then water at the base of the plants rather than over the top so the foliage isn't sitting wet overnight.
Go deep, not often. A quick daily sprinkle barely wets the surface and trains roots to stay shallow, which is exactly what you don't want in a heatwave. Soak the soil until it reaches down to where the roots actually are, then leave it alone for a few days. Before you water, stick a finger into the soil past the first knuckle. If it's still damp down there, skip it.
What to water first, in order:
- New plantings, no negotiation. Anything installed this season doesn't have the root system yet to fend for itself. This is your top priority.
- Containers and hanging baskets. These dry out fast, sometimes daily in this kind of heat. Check them like you'd check a hungry toddler.
- Vegetables that are actively fruiting. Tomatoes, peppers, that kind of thing. Inconsistent water here shows up as cracked or blossom-end-rot fruit later.
- Everything else. Established perennials, shrubs, and lawn have deeper roots and more reserves than you'd think. They can coast through a stretch like this. This is genuinely the part of the garden that needs you the least right now.
What to leave alone this week
No fertilizing. It pushes tender new growth a heat-stressed plant can't support, and fertilizer salts can actually burn roots when the soil's already dry. Wait it out.
No pruning, unless it's dead, damaged, or diseased wood. Cutting is a stressor, and a plant that's already working hard to cope with heat doesn't need another job. It'll keep.
Skip new planting or transplanting if you can push it to a cooler week. If it genuinely can't wait, give it extra water and rig up some temporary shade for the first few days.
Making your garden more heat-tolerant going forward
If this week has you thinking about the long game, a few places to start.
For lawn, overseeding with microclover is the easiest first move. It stays green through drought when regular turf goes crunchy, and West Coast Seeds is a good source if you want to try it. For a full-sun spot where grass has never really worked anyway, creeping thyme or a bee turf mix will handle dry conditions without complaint.
For perennials, these ones shrug off Hamilton summers without much fuss:
- Purple coneflower: handles heat, drought, and neglect with grace, and the bees find it within days of it blooming.
- Black-eyed Susan: completely indifferent to heat once it's settled in, and it self-seeds gently over time in the best way.
- Catmint: soft, drought-tolerant, and blooms for months with almost no care.
- Switchgrass: a native option that handles poor soil and clay without complaint, with great fall colour as a bonus.
- Karl Foerster feather reed grass: one of the best performers for our clay, and low maintenance once it's established.
All of these, plus several cultivars of each, are available at Northland Nursery out in Millgrove, which is where I'd send you first for perennials and grasses.
And mulch. Cedar mulch spread 8 to 10 cm deep is doing real work in a week like this, holding moisture in and keeping soil temperatures down around the roots. If you only get to one long-game task, this is a good one to pick.
A word on you, not just the garden
You're not obligated to be out there in the middle of the afternoon proving a point. Water early or in the evening, wear a hat, keep water on hand for yourself too. If you start feeling dizzy, nauseous, or your heart's racing more than the gardening warrants, that's your body telling you to go inside. The garden will still be there tomorrow. The City runs a heat warning system and opens cool places across Hamilton during a heat event, and you can find the current list at hamilton.ca/heat.
If you're downtown or somewhere with a lot of pavement and not much tree cover, expect it to feel hotter and dry out faster than a yard closer to the escarpment. Adjust your watering expectations accordingly, your microclimate is doing its own thing.
Good things grow, even in a heatwave. Just maybe not this week's begonia transplants.