Summer has officially arrived with a bang. A giant heat dome is creating dangerous temperatures across much of the central, southern, and eastern United States, and forecasters have predicted the arrival of El Niño in 2026—a climate pattern that can amplify heat in some regions and influence weather for months to come.
While everything in the garden will need extra hydration during super hot stretches, some flowering plants are especially susceptible to heat stress and will benefit from a little extra attention when temperatures soar. Expert gardener, cottage garden champion, and sustainability advocate Claire Smith tells Country Living which popular blooms may need additional watering—and a bit of TLC—to make it through a summer heat wave.
Hydrangeas
Hydrangeas, as the name suggests, need a lot of hydration and moisture-rich soil. Claire explains: "They’re hugely fashionable at the moment, and we’re not always helping these plants in our gardens.
"Traditionally, these small shrubs would have been grown on the edge of woodland in dappled or part shade. This is actually their preferred spot. They need moisture and humus-rich soil, often found on the woodland edge. In a heatwave, as their name suggests (hydra), they suffer because they need plenty of water."
Phlox
"A classic traditional perennial," Claire explains. "Phlox are not great in heatwaves because in mid-summer they grow rapidly (leading to more flowers). This young, tender growth is susceptible to wilting, and the plants will stunt their growth or flower less in dry spells."
So ensure these flowers get an extra hydration boost with regular watering.
Roses
Roses can face extra challenges when it comes to the summer season, Claire explains. She urges gardeners not to be alarmed if there's a temporary lack of growth and flowering.
"These days, roses are bred to flower continuously through the summer season. But in heatwave conditions, they often stop flowering and growing altogether," Claire explains.
"New growth may shrivel and dry out; generally, though, all established plants will survive. In my garden, most roses flower again once the hot weather breaks and keep on flowering well into autumn, having gone into a kind of temporary hibernation."
Shade-Loving Plants
"Plants that happily flower in shade, such as fuchsias, hostas, and astilbes, need more attention in the heat," Claire explains.
"These plants are happy to flower in cooler, shady gardens. When temperatures rise to heatwave conditions, these plants often shrivel and are among the first to struggle. Hostas and fuchsias have high water content and are fleshy plants, and astilbes have fine leaves (similar to Acer shrubs) which—with their high surface area—dry out quickly."
