Diascia personata is a much larger, more upright species than the mounding hybrid twinspurs sold for containers — stiff, branching stems carry loose racemes of dusky pink flowers from summer into fall, more at home staked in a mixed border than tucked into a window box. Native to South Africa, it's true perennial only in zones 9–11; further north it's grown as an annual or overwintered from cuttings.
It wants full sun and regular moisture through the growing season, with good drainage to avoid crown rot over winter. Pinching young growth encourages a bushier, more self-supporting habit and reduces the need for staking later on.
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.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Crown Rot
Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.
Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.