Zone: 4 to 9
Soil: sand to clay
Light: Full sun to part sun
Bloom colour: Yellow
Bloom period: August to October
Height: 1 to 10 feet
Moisture: Usually dry to medium
Attracts: A variety of bees, butterflies, birds and small mammals.
Notes: Sunflowers are truly excellent plants for wildlife. The flowers are highly attractive to bees and the seeds that develop will attract finches and many other birds. They also flower for a long time starting in August.
It is best to give sunflowers their own space in the garden because the members of this genus have aggressive root systems and release chemicals that may affect the growth of other plants. This is an adaptation that helps them compete with other plants, so it is not a bad thing. However, you may find it helpful to contain the roots with barriers to prevent the plants from spreading too much.
Inspired by the paintings of Van Gogh, we mostly imagine annual sunflowers; however, there are over fifty species in N.America and nearly all of them are perennial. They are incredibly easy to grow and are one of the essential plants in a late summer or fall garden.
Annual sunflower is native to western parts of North America and is one of the best annuals to attract wildlife. It is a great plant to get kids interested in gardening. Choose a variety that is not pollen free because they are more attractive to wildlife and your children will see the seeds develop thereby learning about the plant reproduction cycle. The varieties with extra large flowerheads often need staking and do not look that great in the garden. There are dwarf varieties available that are only two feet high. These are more suitable for young children. Put them in pots with good soil and keep the soil moist. When the plant starts to wither, remove the flowerheads and let the seeds continue to develop. When you can see the seeds, hang them up for the birds.
Helianthus giganteus grows up to 10 feet high in part-shade in average or moist soil. In more sun and with more moisture, it can exceed 13 feet (4 m) and is one of the tallest perennials in North America. If you find your plants to be too tall, then consider a pruning in late June because the flower blooms are beautiful.
'Lemon Queen' is a manageable infertile hybrid. It has the advantage over the native species in that it is not an agressive spreader and has a long bloom time. This cultivar grows up to seven feet high and flowers for months. It would make a great addition to any flower garden that peaks towards the end of the season. Being infertile, it does not produce seed, so it attracts only pollinators and not birds. In September, these plants are covered with bumblebees.
Most sunflowers need a good deal of sunshine to do well. Helianthus strumosus (woodland sunflower) flowers in part-sun or under open indirect light. You can therefore plant this species on the north side of a building. Its flowerheads are larger than many other members of this genus and it is quite striking. This plant will grow up to eight feet high. It fills in quickly (and that is a nice way of saying that it is a bit of a thug) so give it some room. Another sunflower that handles shade well is Helianthus divaricatus. It is a fabulous plant to boost the colour of your shade beds in the fall, but it will spread quickly if the growing conditions are too good, so be prepared to install barriers. It only grows to about five feet high.
Helianthus mollis is not native to Ontario. It comes from the midwest and grows up to 6 feet high. It has a beautful grayish-green foliage caused by a layer of hairs. Each flowerhead has a double layer of infertile ray flowers that makes these blooms particularly attractive.
Species native to Ontario include: Helianthus couplandii; Helianthus decapetalus; Helianthus divaricatus;Helianthus giganteus; Helianthus nuttallii; Helianthus occidentalis; Helianthus pauciflorus;Helianthus strumosus; Helianthus tuberosus;