Thalictrum flavum Glaucum
The foliage alone would justify this plant. Thalictrum flavum subsp. glaucum carries divided leaves in a distinct powdery blue-grey, unusual enough in a herbaceous perennial to draw comment before it flowers at all. Above them, tall stiff stems hold broad fluffy heads of pale sulphur-yellow flowers made almost entirely of stamens, lightly scented. Flowering runs December to February.
Blue-grey and soft yellow together are a quieter combination than most tall perennials offer, which makes this useful in a border where the colour scheme is already busy. Plant it towards the back, beside water, or in a damp corner where it can be seen against green. It sits well with grasses and other soft-flowered perennials.
Sun or dappled shade suits it, in soil that stays moist through summer, and it will grow taller and stand straighter for it. It tolerates drier ground in shade but flowers less. The stems are strong for their height, though a group in an open position is worth supporting in spring. It dies back completely over winter.
Reaches 1 to 2 m when flowering, over a clump of roughly half a metre.
Trimming: Cut the stems out at ground level in winter once they have browned. Leave the blue-grey basal foliage alone during the season, since it is half the reason to grow the plant.
Deadheading: Little point. The fluffy heads fade gently to buff and hold their shape, and cutting them off gains nothing in flowering.
Fertilising: Compost mulch as growth restarts, with a controlled-release feed underneath it. This one responds well to feeding and to soil improved with organic matter before planting.
Watering: Water deeply and regularly through summer. This is a moisture-loving thalictrum and it shows dryness quickly as shorter stems and browning lower leaves.
Pest Control: Soft spring growth is grazed by slugs and snails. Aphids can build up on the flowering stems in warm weather and wash off with a hose.
Disease Management: Powdery mildew and rust both appear where plants are dry at the root or crowded together. Divide congested clumps every few years and keep the soil moist and mulched.
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