Brook wakerobin is a small, rare trillium endemic to rocky streamsides in the Siskiyou Mountains, a recognized botanical hotspot spanning southern Oregon and northern California. Now classified in the monotypic genus Pseudotrillium, it reaches only 4–8 inches tall and carries white to pale pink petals distinctly spotted with rose or purple. It is widely sought by woodland and rock garden collectors but difficult to source because of its narrow natural range.
It requires consistently moist but sharply drained, humus-rich, slightly acidic soil and cool summers, mirroring its native montane stream-bank habitat. Plants grow from rhizomes and establish slowly; once settled they are long-lived and spread modestly by offsets. The epithet rivale means 'growing by streams.' Mulch with leaf mold to moderate root temperatures and retain moisture. Foliage dies back by midsummer — mark rhizome locations and interplant with low-growing shade groundcovers to fill the gap.
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.
Fungal leaf spot
Brown or purplish spots on the leaves, often ringed with a yellow halo, that spread and merge in warm, humid, or wet weather; heavily spotted leaves yellow and drop early.
Pick off spotted leaves and clear fallen debris to remove overwintering spores. Improve air circulation by thinning, and water at the base so foliage dries quickly. If it persists, apply a copper- or sulfur-based fungicide at the first sign.
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.
Root rot
Plants wilt, yellow, and stunt even in moist soil; lower stems and roots turn brown, soft, and mushy and the plant may collapse. Most common in heavy, wet, or poorly drained ground.
Improve drainage and stop overwatering, and never plant too deep. Lift and destroy badly affected plants along with the soil around the roots. Grow in raised or free-draining beds to prevent it returning.