Dahlia in April: monthly care

Dahlias thrive in full sun and need at least six hours of direct sunlight daily to produce their best blooms. Choose a sheltered spot protected from strong winds, as the tall stems can be brittle. They prefer well-drained loam or sandy soil enriched with plenty of organic matter. Before planting, dig over the soil to a spade's depth and work in a generous amount of well-rotted compost or manure to improve both drainage and fertility. Plant dahlia tubers from March to May once the risk of hard frost has passed, typically late April or early May in most of temperate Europe. You can also plant in September or October in milder areas, though spring planting is more reliable. Dig a hole about 12–15 cm deep and place the tuber horizontally with any visible growing points or "eyes" facing upwards. Space tubers 60 cm apart to allow for their mature spread and good air circulation. For taller varieties over 90 cm, insert a sturdy stake at planting time to avoid damaging the tuber later. Cover the tuber with about 5 cm of soil initially, then fill in the rest as shoots emerge. Water sparingly at first—overwatering dormant tubers can cause rot. Once shoots appear and growth is underway, water more generously. Apply a 5 cm layer of mulch around the base to retain moisture and suppress weeds, but keep it clear of the emerging stems. In colder zones, consider starting tubers indoors in pots during March and transplanting outside in May after hardening off.

Dahlias have moderate to high water needs, especially during active growth and flowering. Water deeply two or three times weekly during dry spells in summer, aiming to keep the soil consistently moist but never waterlogged. Reduce watering in early autumn as flowering slows. Avoid overhead watering, which can encourage powdery mildew and botrytis; instead, water at the base of the plant. Feed dahlias regularly to support their long flowering season. In March and April, as shoots emerge, apply a balanced granular fertiliser or one slightly higher in nitrogen to promote leafy growth. Once flower buds form in early summer, switch to a high-potassium liquid feed (such as tomato fertiliser) every two weeks until September. This encourages abundant blooms and strong tuber development for next year. Dahlias are not reliably hardy in most of temperate Europe (zones 7–9). In November, after the first frost, lift tubers carefully and store them in a frost-free place over winter. Pack them in barely moist compost, sand, or vermiculite in a cool, dark shed or garage at around 5–10°C. Check monthly and discard any that show signs of rot. Common pests include slugs and snails, which can devastate young shoots in spring—use barriers, traps, or organic pellets. Earwigs may damage petals; trap them in inverted pots stuffed with straw. Aphids cluster on buds and shoot tips; squash by hand or spray with soapy water. Powdery mildew can appear in dry conditions; ensure good spacing and water at soil level. Remove and destroy any foliage affected by virus, which causes stunted growth and mottled leaves.