How to grow sunflower

Choose a field that has not grown sunflower, soybean, dry bean or canola for at least 3–4 years — they all carry the same soil rot.

A field coming out of a cereal like maize or sorghum, or a grass, is a good choice — cereals don't share sunflower's diseases and leave the soil in good heart.

Avoid low, wet patches and heavy soil that holds water — sunflower's deep root rots in soggy ground, and heads rot faster in damp air.

Later in the season this same rot shows as a soft brown rot with white cottony mould on the back of the heads — the very thing this long break is protecting you from.

Do this planning about two months before you sow, so you still have time to prepare the field you pick.

Buy certified seed from a registered dealer — a sealed, labelled bag with the variety name and this season's packing date. Pick the oilseed (small black, for oil or crushers) or confectionery (large black-and-white striped snack seed) type to match your market.

Sunflower seed is light — far lighter than maize grain — so a little seed covers a lot of ground. Buy the seed rate your recommendation gives for your field, not by guesswork.

Buy the basal (planting) fertiliser your recommendation lists. Sunflower is a heavy feeder on potash (K) as well as phosphorus (P), so don't skimp on it.

Buy boron now too (a product such as Solubor or borax), so it's ready for the bud stage — dealers don't always keep it in stock, and a boron shortage cannot be fixed later.

Store seed and fertiliser dry, off the floor, away from food, water and children. Keep the label and receipt in case the seed turns out poor.

Clear the field and burn or bury old sunflower stalks and heads — they carry rust (a reddish, dusty spotting) and dark leaf-spots that blow onto the young crop.

Loosen the soil deep — about 15–25 cm, a spade's depth or more — so the taproot can drive down and rain soaks in. Sunflower pays back deep tillage more than most crops.

Break the clods on top to a fine, crumbly tilth, so the small seed sits snug in moist soil and comes up evenly.

Level the surface and make sure water drains away — on a slope, work across the slope, and open a channel to drain any low, wet spots. Sunflower hates wet feet.

Use only well-rotted manure or compost — dark, crumbly, no strong smell. Fresh, strawy manure needs more time to rot down.

Spread it evenly and thinly over the field — a good gauge is one full wheelbarrow-load over about a 10-pace by 10-pace patch, which comes to 5–10 tonnes a hectare (t/ha).

Work it into the topsoil 1–2 weeks before sowing so it settles in with the soil.

Sow into warm, moist soil — at least 12 °C (soil that already feels comfortably warm to your hand in the morning). Cold soil rots the seed before it sprouts.

Open your rows about 60 cm apart — a bit over two hand-spans — or the row width your recommendation gives (wider rows in drier zones).

Space the stations a hand-span apart (about 25 cm) and drop one seed per station. Use the population your recommendation sets — fewer plants in dry areas give bigger heads.

Sow one finger-joint deep (3–5 cm), and never deeper than about 6 cm. A little deeper in dry, sandy soil; shallower in heavy, wet soil.

Place the basal fertiliser — the amount your recommendation gives — half a hand's width (about 5 cm) to the side of the seed and a little below, never touching it, or it burns the sprout.

Cover and firm the soil over both, so the seed sits snug in moist earth and comes up strongly.

Walk the field twice a week, in a big 'W' so you cover the corners and the middle, not just the edge by the path.

Cutworms: look for young plants cut clean off at ground level (worst in the morning). Scratch the soil nearby to find the fat, grey, curled caterpillar and destroy it.

Birds: look for holes where seed was dug out and missing plants in patches, especially along the field edges — scare them off the young field early.

Downy mildew: look for seedlings that are stunted and pale, with white cottony growth on the underside of the leaves — pull these out and remove them; they won't recover.

Count the gaps (stations with no plant) so you know whether to replant or gap-fill.

About 1–2 weeks after sowing, walk the rows and count how many plants came up against the number of stations you sowed.

Work out the share that came up (for example, 80 plants from 100 stations = 80%).

80% or more → a good stand, carry on.

If it fails — below 80% → replant or gap-fill the biggest gaps in the next few days, while the soil is still moist and the crop is only days old. Gaps caught now can be filled; a week later they can't.

Once the seedlings are up (about 10–18 days after sowing), check for any station with more than one plant.

Keep the strongest seedling and snip the others off at ground level with a knife — don't pull them, or you loosen the roots of the one you keep.

Aim for one strong plant per station at the spacing your recommendation set — remember, fewer, evenly spaced plants grow bigger heads.

Keep the topsoil moist but not waterlogged — sunflower seedlings rot in standing water.

Water about every 5–7 days, more often in heat and on sandy soil that dries fast.

Check by pushing a finger into the soil: water when the top few centimetres are dry.

Walk the field twice a week in a 'W', checking about 10 plants at several stops.

Downy mildew: look for stunted plants with leaves pale or yellow on top and white cottony growth underneath — remove affected plants.

Leaf-eaters (defoliators — caterpillars and beetles that chew leaves): look for chewed, holed or skeletonised leaves and the insects doing it. A few chewed leaves on a healthy plant is not a crisis — sunflower can carry some leaf loss.

Count the leaves: as plants reach 8–10 true leaves, get ready to apply boron (next task) — it must go on before the bud shows.

Weed the first round about 2–3 weeks after sowing, before the weeds get bigger than the crop.

Weed a second round about 4–6 weeks after sowing, before the leaves close over and shade the row.

Hoe shallowly near the plants — sunflower has spreading surface roots and a taproot just below, and deep hoeing cuts them.

In dry areas, leave the pulled weeds lying between the rows as a mulch to hold moisture.

Apply at the 8–10-leaf stage (about 4–6 weeks after sowing) — before the flower bud appears. This window does not come back.

Use exactly the boron amount your recommendation gives — no more. Boron helps in a tiny dose but poisons the plant in excess; the safe range is narrow.

Mix it fully with clean water so it all dissolves — undissolved lumps scorch the leaves and waste the dose.

Apply as a foliar spray (sprayed straight onto the leaves) or watered into the soil, as your recommendation says — a foliar spray is surest on sandy or chalky soils.

Spray safely: cover your skin, eyes and nose, spray in the cool of the day with the wind behind you, keep it off food crops, and wash well afterwards.

Side-dress at the 8–10-leaf stage (about 4–6 weeks after sowing), around the same time as the boron.

Band the nitrogen your recommendation gives a hand's width (about 10 cm) to the side of the row — not on top of the plants.

Apply on moist soil (after a weeding or light rain) and cover it or water it in, so it doesn't gas off into the air and go to waste.

Keep the fertiliser off wet leaves (it sticks and scorches them) and wash your hands afterwards.

Water about every 7–12 days, depending on heat and soil type.

Let the deep root do some work — a little drying between waterings drives roots deeper, which pays off in later drought.

Don't let the crop wilt badly during this fast-growth stage, though — it sets the size of the plant.

Walk the field twice a week and check the leaves, stems, and the face and back of the heads on about 10 plants.

Sunflower rust: look for reddish-brown, dusty pustules (raised spots) on the leaves, mostly on the underside — they rub off like rusty powder. Heavy rust dries the plant out early.

Sclerotinia head rot: look for a soft brown rot on the back of the head, often with white cottony mould and hard black lumps — it can drop the whole head.

Sunflower head moth: look at the face of the head for small caterpillars, with webbing and sawdust-like droppings among the developing seeds.

Do not reach for insecticide during flowering — it kills the bees. Note what you find; act after bloom, or open the matching pest guide.

Keep the soil moist right through budding and flowering — this beats every other watering in the season.

Water about every 5–7 days, more often in heat.

Never let the crop wilt at this stage, even for a single day.

Do not spray any insecticide while the crop is in flower — bees working the heads will be killed.

If a pest truly must be controlled, act before flowering, or choose a bee-safe product and spray in the evening when bees are not flying — but at full bloom, the safe choice is usually to leave it.

Welcome bees: keep some flowering weeds on the field edges and a little water nearby, and don't burn or disturb wild bee nests around the field.

Where neighbours flower at the same time, the bees are shared around — planting together helps everyone's heads fill.

Start scaring as soon as the seeds begin to fill (from about 10–11 weeks after sowing), not once the damage is already bad.

Be present — walk the field, especially early morning and late afternoon, when birds feed most.

Use movement and noise: reflective tape or old discs that flash, bangers and clappers, tin-can rattles, and scarecrows that you move every day or two.

On small plots, netting over the heads is the surest guard of all.

Watch the field edges and any early-ripening heads first — that is where birds start.

Once a week, look over the standing crop and check a few stalks.

Charcoal rot: look for plants that ripen and die too early and wilt; split a lower stalk and look for greyish, shredded pith peppered with tiny black specks, like charcoal dust.

Lodging: look for plants leaning or fallen, especially after wind — feel for soft, rotted or hollow stalk bases.

If charcoal rot or lodging is spreading, harvest the affected heads early rather than lose them to the ground and the birds.

Keep watering through early seed-fill, about every 7–10 days, while the leaves and the back of the head are still green.

As the back of the head yellows and the lower leaves dry, reduce the watering.

Stop once the head is turning brown and drooping, so the crop can dry down for harvest.

From about 13–14 weeks after sowing, check a few heads from different plants across the field.

Look at the back of the head: ripe heads turn from green → yellow → brown and bow over, facing down, and the leafy bracts at the edge go brown and papery.

Check the seeds: they should be hard and fully coloured — solid black for oilseed types, black-and-white striped for confectionery (snack) — and the little flowers on the face should have dried and fallen.

If it is not ready — backs still green, seeds soft → wait, and keep scaring birds. If it is ready — backs brown and drooping, seeds hard → move to harvest before birds, wind or shatter take the crop.

Harvest once the crop passes the maturity check — backs of the heads brown and drooping, seeds hard and fully coloured, and the face florets shed.

Cut each head off with a hand-span of stalk (about 25 cm) left on, so you can carry it and hang it to finish drying.

Work in dry weather, and lay the heads face-down or hang them, so any dew or rain runs off instead of pooling in the seed.

Don't delay — if birds, storms or lodging threaten, cut now even though a few heads might have ripened a little more.