🌿 Sunflower

Grow in fertile, well-drained soil (loam or sandy loam) with good aeration; avoid heavy, waterlogged sites. Add organic matter or compost to improve moisture retention and nutrient supply, but ensure that excess water can drain away. Best performance is obtained in slightly acidic to neutral soil (approx. pH 6.0-7.5). In containers, use a draining potting mix and provide drainage holes.

Sow directly after the last frost, when the soil has warmed up (approx. 10-15°C), in full sun. Sow seeds 2-3 cm deep in well-drained, fertile soil; keep seedbed evenly moist until germination (usually 7-14 days). Thin seedlings to final spacing: around 30-45 cm for dwarf/branched types and 45-60 cm (or more for very tall cultivars) for tall single-stemmed types; leave 60-90 cm between rows. Water regularly during establishment to avoid waterlogging. If you're starting indoors, sow in individual pots 2-3 weeks before the last frost and harden them off; transplant carefully, disturbing the roots as little as possible, as sunflowers don't like root damage. Protect young plants from slugs, snails and birds, and provide support for tall varieties in exposed sites.

Sunflowers generally need only moderate fertility. Before planting, incorporate compost or well-decomposed manure and (ideally) base any additional fertilization on a soil analysis. If no analysis is available, incorporate a balanced, low-to-moderate nitrogen fertilizer at the time of planting (for example, a general garden fertilizer such as 5-10-10 or similar) at label rates. Avoid heavy applications of nitrogen, which encourage lush foliage and weaker stems with fewer flowers. For garden beds: if plants show slow growth or pale leaves, carry out a border treatment once when plants are about 30 to 45 cm tall with a small amount of balanced fertilizer, keeping it a few centimetres from the stem and watering it in. A second light application can be made at the start of bud formation on poor soils; otherwise, there's usually no need for additional feeding. For containers: use a slow-release balanced fertilizer mixed with potting soil at planting, or feed with a diluted liquid balanced fertilizer every 2 to 4 weeks until buds form; then reduce the amount. General advice: do not apply fertilizer to stems/leaves, water after application, and give priority to phosphorus and potassium over nitrogen if flowering and strong stems are the objective.

After planting and once the soil has warmed up, apply a 5-8 cm layer of organic mulch (compost, straw, shredded leaves or aged bark) to conserve moisture, moderate soil temperature and suppress weeds. Keep the mulch 5 to 10 cm away from the stem to reduce the risk of stem rot and pests. In cool, damp conditions, use a thinner layer and avoid piling mulch against young plants; top up as it decomposes over the season.

Secure tall or large-headed sunflowers (especially branching and giant cultivars) in exposed or windy locations. Insert a sturdy cane, bamboo rod or metal stake 20-30 cm from the stem when plants are still young, to avoid damaging the roots; drive the stake 30-45 cm into the ground. Tie the stem with flexible ties (garden twine, fabric strips or horticultural tape) in the shape of a figure-of-eight, adding more ties as the stem lengthens; avoid too-tight ties, which risk girdling the stem. For very tall plants, use two stakes or a sturdy post and add a second tie near the top third once the flower bud has formed. In the rows, a line of horizontal twine stretched between the end posts can provide support for several plants. Grouped plantings and shelter from strong winds reduce the need for stakes.