Sunflowers are annual flowers that anyone can grow. The only requirement that they absolutely need to thrive is 10 or more hours of sun a day. They are so reliable that you can plant seeds that you bought in the supermarket provided they have not been shelled or roasted. If you must plant sunflowers in a shady spot, make sure they have morning shade and afternoon sun. Sunflowers come in a range of colours, flower shapes and heights so chances are there is a sunflower just right for your garden.
The easiest way to start sunflower seeds is to plant them directly in the garden when soil temperatures warm up to 10 degrees C (50F). Plant seeds 2.5 to 5 cm (1 to 2 inches) deep in loose soil from mid-April until mid-July depending on the variety. Sunflowers reach maturity, the time from germination to when seeds are ready to harvest, in 70 to 90 days. The longer the days to maturity the earlier the sunflower should be planted. So plant sunflowers like giant mammoth that mature in 90 days in April or May. Space seeds for dwarf or miniature varieties 30 cm (1 foot) apart and space sunflowers with a mature height of up to 3 metres (10 feet) at 60 cm (2 feet) apart. Giant varieties should be spaced 90 cm (3 feet) apart. Keep the seeds evenly moist and they should start to germinate in four to six days.
Starting seeds indoors
Start sunflower seeds indoors two to three weeks before your final frost date. Start sunflower seeds in individual pots filled with a sterile seed starting mix. Place one or two seeds in each pot at the same depth you would outside. Place in a sunny location and keep them evenly moist. If you plant two seeds per pot remove the weakest seedling. When all threat of frost has passed harden off your sunflower seedlings by placing outdoors in a protected location -- a shaded spot that protects the seedlings from wind -- during the day. Bring them indoors at night. After hardening off for about a week, plant your sunflowers in the garden.
When your sunflowers reach 10 to 15 cm (4 to 6 inches) high, spread 5 cm (2 inches) of compost or well rotted manure around the base of the plants. Do this again just as the buds start to open. Sunflowers will tolerate short periods of drought. However, for the best and biggest blooms, give your sunflowers at least 2.5 cm (1 inch) of water a week. Tall sunflowers occasionally need to be staked, particularly ones planted in sandy soils. For individual sunflowers use a 1.8 metre (6 feet) length of bamboo cane inserted 30 cm (12 inches) into the soil. Secure the sunflower to the bamboo in three or four places using twine or elastic plant ties. If you have a block of sunflowers growing closely together, loosely encircle the entire block with twine halfway up the plants and again right below the top flower heads.
In the garden
Sunflowers come in a multitude of colours and sizes -- use them anywhere you need a mid to late-summer splash of colour. Use mid-sized or giant sunflowers as temporary hedges or to hide an eyesore. You can even use them to create simple mazes or forts for adventurous children. Dwarf sunflowers make wonderful additions to containers and window boxes. Or use them in the garden to define plantings or edge walkways. Sunflowers also do well in the vegetable garden. Plant them on the north-east side to prevent shading of sun loving veggies. Use them in cutting gardens, but remember for sunflowers that only produce one flower, once you remove that flower it will not produce another one. Any size of sunflower is good for wildlife gardens as they provide food and shelter for bees, birds and butterflies.
To grow sunflowers in containers, use a general purpose potting mix. Either plant seeds directly into the container or use seedlings started indoors. Plant dwarf sunflowers in containers as small as 10 cm (4 inches) in diameter. For medium-sized sunflowers use half whisky barrels or containers with a diameter of at least 35 cm (14 inches). The larger containers will keep the weight of the sunflower from tipping the container over. Keep the soil in the containers moist but not soggy. Fertilise unflowers monthly with a 10-10-10 liquid fertiliser or a handful of compost mixed into the top 1.25 cm (1/2 inch) of soil.