Sunflower Cover Crop Seed

Sunflowers are one of the best summer cover crop species for drawing in bees and beneficial insects, which is why they are a common part of multi-species blends. Common Sunflower also has a robust root system that captures soil nutrients and helps control erosion. Sow once the soil is over 14°C, at 5–8 kg/ha on its own. For more diversity, our Cover Crop Plus Summer Mix combines sunflowers with buckwheat, cowpeas, millet, chicory, Winfred forage brassica and tillage radish.

A sunflower cover crop is a good choice, because sunflowers host mycorrhizal fungi and support their growth. Long bare fallows run these fungi down, and crops sown afterwards can struggle to take up phosphorus and zinc. Canola and other brassicas, including radish, and lupins don't host mycorrhizal fungi, so a summer sunflower, or a mix that includes it, helps keep soil infectivity up. Sow Common Sunflower once soils are over 14°C, at 5–8 kg/ha on its own.

Sow Common Sunflower once the soil temperature is over 14°C. In most of WA that means late spring into early summer, and it pays to plant on rising soil temperatures for quicker, more even germination. Sow into moist soil, ideally after a good summer rain or under irrigation, because the crop needs moisture to establish and keep growing through the heat. Sunflowers survive best in soil above pH 5 (CaCl2), so check your soil test before choosing a paddock.

Sow Common Sunflower at 5–8 kg/ha on its own. In a cover crop blend it makes up only part of the seed, so the overall rate is set by the mix: our Cover Crop Plus Summer Mix, which includes sunflowers among seven species, is sown at 15–20 kg/ha in total. Use the higher end of the sunflower range where soil moisture is good and you want a dense, weed-suppressing canopy, and keep seed-to-soil contact good with a well-prepared seedbed.

Sunflowers are well suited to heavy soils. Common Sunflower's ideal soil range is heavy (clay) soils with a pH above 5 (CaCl2), in areas with 350 mm or more of rainfall, and its robust root system draws up nutrients and helps hold the soil against erosion. Deep soils without subsoil constraints give the best results. Sow at 5–8 kg/ha once the soil is over 14°C, into moist soil. Slash before flowering if you want the biomass returned to the soil.

Sandplain isn't the best fit for sunflowers. Common Sunflower is suited to heavy soils and survives best above pH 5 (CaCl2), so acidic sands need lime first and still won't suit it well. If you want a summer cover on lighter country, a multi-species blend spreads the risk: our Cover Crop Plus Summer Mix suits light sands through to heavy soils with pH 5 (CaCl2) and above, and 350 mm or more of rainfall, with other species carrying the lighter ground.

Slash it before it flowers. Where sunflowers are grown for the cover crop effect rather than for seed, slashing before flowering returns the biomass to the soil while the stems are still soft. Leaving the mulched material on the surface keeps the soil covered, helps water soak in and adds organic matter as it breaks down. In a mixed cover crop, time the slashing for the whole blend, not just the sunflowers, so companion species have done their job too.

Include sunflowers. Their strong, tall stalks support companion species, their robust roots capture nutrients and help with erosion control, and their flowers bring in beneficial insects. Our Cover Crop Plus Summer Mix is built that way: sunflowers with cowpeas, millet, chicory, Winfred forage brassica, tillage radish and buckwheat, for biomass, nitrogen and soil structure. It is sown in spring at 15–20 kg/ha, suits light sands to heavy soils, and can be grazed, mulched or left to stand.

Common Sunflower suits areas with 350 mm or more of annual rainfall, but because it grows over summer, what matters most in WA is moisture in the soil at sowing and through the hot months. Sow into a moist profile after good summer rain, or under irrigation, once the soil is over 14°C. Deep, heavier soils that hold more water give the crop its best chance, and a sunflower stand left without moisture through summer will struggle to produce much biomass.

It isn't the right seed for that. Common Sunflower is sold for cover cropping, valued for what it does for the soil and the insects it brings in, and it is not a named oilseed variety selected for grain yield or oil content. If you want a commercial oilseed or birdseed crop, talk to your agronomist about suitable varieties and a marketing plan before sowing. For cover cropping, sow it at 5–8 kg/ha once the soil is over 14°C, and slash before flowering to return the biomass to the soil.