Thalictrum is the finest-textured tall plant in the cutting garden — blue-grey maidenhair-like foliage topped by loose clouds of tiny lavender-purple flowers on tall, almost black stems. It reads as mist in an arrangement, softening everything around it and adding height without weight. It is the definition of airy.
Thalictrum rochebrunianum is the most useful species for cutting — taller and longer-lasting than other species. It prefers the conditions of a woodland edge: rich soil, consistent moisture, and some protection from hot afternoon sun. Slow from seed (needs cold stratification and two seasons to reach flowering size), so start from transplants or divide established clumps in early spring. Once settled, it is reliably perennial and virtually trouble-free.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.