Posted: 20/02/2015 at 17:11
August is prime weather for sunflowers. I grow them each year from a March sowing and later even into May sowings. I find the key is good position and plenty of food. Tall varieties need staking and larger blooms can be obtained by stopping emerging side shoots, you can get them to the size of a very large plate with a good regime. They are easy to grow, sow decide where, somewhere that gets full sun for as long as possible, and feed the soil before planting, plenty of well rotted manure or compost. Guard them against slugs, and feed weekly with liquid seaweed. Water very well.
You'll be growing in numbers so get prepared early and make successive sowings with several varieties, the smaller varieties produce many heads. Stop sideshoots early, just like you do with tomatoes and get some 8ft canes, taller of you can and tie in every few days depending on how fast they grow. Wind will be your enemy so a sheltered position is advisable.