When to Plant
Sunflower seeds can be planted after the danger of a hard frost has passed. The timing varies from region to region from the end of March to May. Check your seed packets for the length of time from germination to flowering to estimate when your sunflowers will be in bloom. Some quick growing dwarf varieties can be planted as late as end-June for Autumn blooms. If you would like a prolonged display of blooms, consider succession sowing (plant seeds as soon as the prior planting sprouts, for the first month of the sowing season). Be sure to give yourself space between seeds for future sowing!
Sunflowers are hungry plants! Make sure your soil is rich in nutrients. If you have natural sources such as well-rotted manure or ash from wood burning stoves fantastic. Wood only, if you use coal do not add coal or mixed ash to your soil! Otherwise enrich soil with good quality flower and fruit fertilisers. Your container or garden bed should be full of rich and relatively weed-free loose soil.
It is always worthwhile to germinate seeds a few days prior to planting. Create a mini greenhouse with damp kitchen paper and a ziplock bag to test if your sunflower seeds are viable. It is as easy as wetting kitchen paper, placing it in a ziplock bag and sprinkling your seeds inside. Close the bag, place it on a window cill and wait. A few days later your seeds will have sprouted and are ready to plant either in your container of choice or in a prepared garden bed. Plant your seeds where you want them to bloom. Sunflowers, unlike other plants, do not like to relocate!
Sunflowers like full sun and a relatively protected area (the taller ones in particular are susceptible to wind damage). Aim to plant taller varieties near fences or walls for wind shelter.
Plant seeds at least 6 inches or 15cms apart (more if you are succession planting to allow space for planting future seeds) and cover them with loose soil. There should be about a 1/2" or .5cm of soil on top of the seeds. If dry, water the area gently with a sprinkle rather than a flood of water so as not to upset the seeds. Water the sunflower bed in very dry periods - don't let the soil completely dry out. In about 10 days expect to see your seedlings - two very fat green leaves emerging from the earth!
Unfortunately lots of critters love sunflowers as much as we do. If slugs are your garden enemy, look for organic, non-toxic slug control pellets at your local garden centre. Other four-footed pests can be dissuaded by companion plants. Chives, garlic, oregano and thyme repel both insects and four-footed critters. Plant in and around your sunflower patch to keep them at bay.
When the blooms arrive they are beautiful in situ and make wonderful gifts. For the longest enduring cut flowers, cut blooms just before they open and place them in a vase or a bucket with lots of cool water. Watch the water levels and replenish often as the blooms are thirsty.
Harvesting and saving sunflower seeds for next year is easy and thrifty. Make sure that your sunflower variety is heirloom (not hybrid). Leave the blooms on the stalk and wait for the base of the blooms to turn brown. Cut the seed head off the stalk, place it in a brown paper bag and store it a dry warm location. Remove the seeds from the seed head (a messy job so wear gloves and cover the area with newspaper). Save the seeds in an airtight container in a dry area until next spring (moisture is the enemy of seed savers). Verify your saved seed viability with the ziplock seed germination test above.
More tips for growing and seed saving here.