Scabiosa is one of the best long-season cutting flowers — the domed, lavender-blue pincushion flowers on long wiry stems bloom continuously from midsummer well into autumn if you keep cutting them. The perennial species (S. columbaria and its cultivar 'Butterfly Blue') are compact and free-flowering; annual scabiosa (S. atropurpurea) blooms the first year from seed and offers a wider color range.
The more you cut, the more it produces. A plant that is allowed to set seed will shut down production — keep deadheading or cutting and you'll have flowers for months. The tall-stemmed flowers work beautifully in mixed arrangements and are especially effective with grasses, nigella, and late-season cosmos.
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.