From Scott Kunst, Old House Gardens Friends of Old Bulbs Gazette
High heat has plagued much of the country this summer. Some bulbs like it, but others suffer. Dahlias, for example, have struggled or failed in many gardens where they usually thrive. That’s because they come originally from the mountain plateaus of Mexico where days are hot but nights are dramatically cooler. When nights are too warm, dahlias just can’t grow well. Some varieties are more sensitive than others and can even die. The good news is that if you can keep them going till temperatures cool (which has to happen sometime, right?), they’ll kick back into gear and bloom gloriously till frost.
Glads may develop kinked stems in unusually hot weather as they sag a bit during the day, unable to fully replenish the water evaporating from them, and then grow upright at night when evaporation slows. This is most often a problem with glads like ‘Atom’ that have thin, wiry stems. To help, keep your glads well-watered and protect their shallow, wide-spreading roots from disturbance. Tiny sucking insects called thrips proliferate when it’s hot, too, and can leave glad leaves and blossoms mottled, or even prevent buds from opening. Here are tips on control of thrips.
Heat affects flower color, too. Deep-colored lilies such as ‘African Queen’ may be paler in high heat, bicolor dahlias such as ‘Deuil du Roi Albert’ may bloom temporarily as solids, and the rosy tones of ‘Kaiser Wilhelm’ and others won’t develop fully until the weather cools.
Of course some bulbs love the heat. In many gardens this summer, cannas, tuberoses and rain lilies have been especially happy — and we hope you’ve been enjoying them.