Lupin in March: monthly care

Lupins thrive in full sun or partial shade, though flowering is strongest with at least six hours of direct sunlight daily. They prefer sandy soil or loam with good drainage and slightly acidic to neutral pH; avoid heavy clay or waterlogged ground, as lupins are prone to root rot in poorly drained conditions. Before planting, dig over the soil to a spade's depth and incorporate some well-rotted compost or leaf mould to improve structure, but don't add lime or manure, which can inhibit the nitrogen-fixing bacteria in their roots. Plant lupins in March, April, September or October. If planting container-grown specimens, dig a hole slightly larger than the root ball, set the plant at the same depth it was growing in the pot, and backfill with soil, firming gently. Space plants 45 cm apart to allow for their mature spread of 40–60 cm. If sowing seed directly outdoors, sow in March or April after the last hard frost, or in September for germination the following spring. Scarify the hard seed coat with sandpaper or nick it with a knife to improve germination, then sow 1–2 cm deep. Water thoroughly after planting to settle the soil around the roots. Apply a 5 cm layer of mulch around the base, keeping it clear of the crown to prevent rot. Young plants may need staking in exposed sites, as the tall flower spikes—reaching 80–120 cm—can be top-heavy. Lupins establish a deep taproot, so avoid transplanting once settled.

Water lupins regularly during their first growing season to help establish the deep taproot, especially in dry spells. Once established, they have moderate water needs; water deeply during prolonged dry periods in spring and summer, particularly when buds are forming and during flowering. Reduce watering in autumn and winter, as lupins are dormant and excess moisture around the crown can cause rot. Feed in March and April as new growth emerges. Apply a balanced general-purpose fertiliser such as blood, fish and bone or a slow-release granular feed, scattering it around the base of the plant and watering in. Avoid high-nitrogen fertilisers, as lupins fix their own nitrogen through root nodules and too much can promote leafy growth at the expense of flowers. A light top-dressing of compost in early spring is also beneficial. Lupins are fully hardy in zones 4–8 and need no special winter protection in temperate Europe. Mulch around the base in autumn with compost or bark to suppress weeds and retain moisture, but keep mulch away from the crown. Common problems include aphids, which cluster on young shoots and flower spikes in spring—hose them off or use an insecticidal soap. Lupin anthracnose, a fungal disease causing brown spots on leaves and stems, can be serious; remove and destroy affected foliage promptly and avoid overhead watering. Powdery mildew may appear in dry summers; improve air circulation and water at the base. Slugs and snails target young foliage in spring, so use barriers or organic pellets if necessary.