Amazing annuals: Helianthus

Loved by bees and children alike, annual sunflowers can be sophisticated too.

When it comes to being useful, plants don’t get much better than the common sunflower (Helianthus annuus). The seeds are edible (and good for you), and yield oil, the pulp is used for stock feed and we pay over the odds for sunflower seeds to feed wild birds. The plants themselves can be fed to livestock, young plants can be used as green manure, old stems are great for composting and young seedlings can be used as sprouted seeds. Being vaguely related to globe artichokes, the young flowerbuds can be eaten, though I have never tried. Apart from the readily available ‘Russian Giant’ most of the common sunflowers, available to gardeners, have small seeds that are not much good for eating. In fact, some of the modern kinds, described as ‘pollenless’ may not form seeds at all. They have been bred as cut flowers and it seems that people that buy sunflowers as cut flowers dislike the pollen that drops from the heads as each tiny flower in the ‘disc’ opens. It means that the flowers last longer too. Presumably, though I have not tested this, there is nectar for the bees even though there is no pollen.

The plant has been grown in Europe since about 1510 but had been cultivated in Mexico for thousands of years and then throughout what is now the southern states of the USA. It is no wonder that it was so highly valued, as a foodstuff as well as for its ornament, with huge flowers resembling the sun. The flowers are not just bright and cheerful but the placement of the disc florets is a fine demonstration of the Fibonacci series with spirals of flowers, left and right, according to the Fibonacci numbers. It is wonderful when a simple flower can teach us so much.

The tallest sunflowers tend to have one large flower at the top of the stems but modern varieties branch lower down so can have a longer succession of blooms. A failing of the plants for the garden is that they are bulky and coarse with large, heart-shaped leaves and are not in bloom for long. A good proportion of gardeners just want to see their plants as big as possible and don’t care but modern sunflowers can have a place in an attractive garden.

Before I get on to cultivation, a word on new kinds. When dealing with calistephus I mentioned the green-flowered ‘Hulk’. The latest thing in sunflowers is a lack of ray florets (petals). The ‘Sun Fill’ series has ‘flowers’ with enlarged bracts around the heads and no ‘petals’. I have yet to try them, so perhaps I should hold my tongue, but I am rather at a loss as to what the appeal is. Completely different are the ‘Sunbelievable’ sunflowers from Thompson & Morgan. These are remarkable, bushy and flower endlessly, because they do not set seed. But they have to be bought as plants and cannot be grown from seed.

Even without these exceptions, there is enough variety for anyone. There are doubles, of various shapes, large flowers, small flowers, tall plants, dwarf plants and a wide range of colours from cream to purple.

Sunflowers can be sown just where they are to grow. Their growth is so rapid that this is a good way to grow them but delay sowing till late April because they don’t like frost. And do you remember that animals like to eat them? Well protect sown seeds from birds, mice and slugs. I would sow two seeds per station, at distances of about 30cm for the smaller kinds, to 1m apart for the giants. You could cover them with a little cloche made of a cut-down plastic bottle.

You can sow them inside too but never sow them too early. It is a mistake to have straggly seedlings waiting to be planted out. They are at the perfect stage when they are about 10cm high with the two seed leaves and another pair of true leaves. If they get stunted and receive a check they will flower when small and not reach their full potential. Sow one or two seeds per pot, keep at about 20c and if two seedlings grow, pinch out one. If you are growing giants then keep the larger of the two. If growing a mixture of colours try to keep a mix of the large and small seedlings to ensure a mix of colours.

Plant sunflowers in a bright spot. How big the plants get is partly genetic but largely up to you. If grown in rich soil, with lots of compost and water they will get big and robust before they start to flower. The same plants, if starved, will flower when tiny. It is an often-repeated dictum that annuals must have poor, dry soil to do well. This has some basis in fact but is not really true and absolutely wrong with sunflowers. The best I have grown lately was in soil that was dug over with lots of manure added and then mulched with a 15cm layer of manure. It is true that the plants did not flower quickly but they made huge plants before they bloomed and were them enormous fun.

And Happy New Year!

3 Comments on “Amazing annuals: Helianthus”

  1. tonytomeo
    December 31, 2020 at 8:35 pm #

    Does anyone really know what species of sunflower is the State Flower of Kansas, or is it just ‘sunflower’? I do not know how which species are native there.

    • thebikinggardener
      January 1, 2021 at 3:42 pm #

      It seems it is the annual sunflower.

      • tonytomeo
        January 3, 2021 at 12:48 am #

        That makes sense, and I would trust that website more than others, but some insist that other species are the State Flower of Kansas. Several State Flowers are like that, such as the Yucca of New Mexico. Some insist that California has two State Trees, both species of redwood! Well, regardless, I would go with the Helianthus annuus.

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