Where areas aren’t required for crops or bedding or if you simply plan to give a garden bed a rest, put the area to good use by sowing sunflowers.
Not only will they look very attractive in a group, sunflowers act as a cover crop protecting soil and inhibiting the growth of weeds. They can be used on land set-aside to attract beneficial insects and improve bee forage in the summer and autumn while acting as a green manure for future crops.

Sunflowers can be used as a biological control, planted along field margins to attract insects which control pests affecting crops. Most commonly used in companion plantings alongside corn, cucumber and tomato crops, they are especially useful at attracting beneficial insects which prey on aphids.

Used as a spring-sown green manure or cover crop, the fast growing foliage will help suppress weeds, producing lots of organic matter while making an attractive groundcover. The roots leave a good tilth for following crops.
Sunflowers have highly efficient root systems and can be grown in areas which are too dry for many other crops. Roots can break up hardpan, kill weeds, and pull up insoluble subsoil phosphorus from minerals up to the topsoil to make available for next crops. The plant has a strong taproot that can penetrate the soil to depth of 3 metres. It also has a large lateral spread of surface roots. The roots release a chemical that has allelopathic effects which inhibit the growth nearby plants and weeds.

Sunflowers are a fast growing warm season annual, planted in mid-May they will likely have beautiful heads by mid August. They make a lovely cut flower and are ideal for wildlife-friendly planting schemes. Rich in both nectar and pollen the flowers attract bees, butterflies and other pollinating insects like a magnet.

Sowing Period: March-June or indoors from late February
Soil: Most soil types, succeeds in poor and dry soil
Growing Period: 4 months to flowering
Flowering period: Yellow flowers in midsummer to early autumn
Height: 180 to 240cm (6-8ft)
Qualities: Weed suppressor. Bee plant. Drought resistant.
Coverage: 13.5kg per acre - 100gm covers 30 square metres

Sowing: Sow outdoors March to June
Sow directly outside as early as possible to miss heavy frosts (mid-April through mid-May), to germinate in about 1 to 3 weeks. Prepare the soil by removing weeds, digging over if it hasn't been recently cultivated and raking level.
Seeds can be scattered very thinly over the surface of the soil or can be placed into the soil in a block arrangement. Sow 5cm (2in) deep.
For flower borders space 45cm (18in) apart. If complete coverage or high yields take priority over beauty, plant the seeds closer, in a 30 x 30 cm block, (12 x 12in). Rake the surface of the soil and water in well.
If earlier flowers are required, seeds may be started indoors in pots as early as February or March, and planted out in April or May. Seedlings resent root disturbance, so sow into deep pots and plant into the garden as soon as you are able.

Cultivation:
An easily grown plant, sunflowers succeed in most soils including poor soils provided they are well-drained. Established plants are quite drought-resistant except during flowering. Make sure that seeds are covered, if the birds discover the free feast you’ve laid out for them you may need to cover the bed with a net. Protect from slugs during the seedling stage.
Once flowering is are over, heads can be left or harvested for bird feed. Dig up plants and add to the compost. The stems can be tough may need to be smashed or shredded before composting.
The long dry stems can be left to dry and burnt for their high potash content, the ash is rich in potassium.
You can extend the weed-management benefits and allow its allelopathic effects to persist longer by leaving killed residue on the surface rather than incorporating it. Allelopathic effects taper off after about 30 days.
Sunflowers can be planted thickly to give a 'flowering fence'. In exposed sites the flowers may protection from high winds

Harvesting Seed:
To dry sunflower seeds, cut the heads off when they begin to yellow at the back and hang them upside down in a dry location away from rodents and birds.
Once dry, rub the seeds off and soak overnight in 4 litres 1 gal) of water with 1 cup of salt in it. Roast dry in an oven at 120°C(250°F) for 4 to 5 hours and store in an airtight container.

Plant Uses:
Green Manure/Cover Crop, Bee Plant, Butterfly Garden, Wildflower Gardens or Wildlife Gardens, Cottage/Informal Garden, Flower Arranging.