Sunflowers are grown for their blooms, so sunflowers not flowering is a big problem. There are many possible factors, so getting to the root of the problem may require some trial and error. However, solve the issue and you’ll hopefully be rewarded with beautiful blooms and will be able to avoid the same problems next year.
Setting yourself up for success when you first plant your sunflower seeds is vital in ensuring blooms, though it is not a guarantee. ‘Sunflowers are easy for beginners to grow and often germinate quickly as the temperatures increase in May,’ says Chris Bonnett, founder of the online garden centre GardeningExpress. ‘Sow directly outdoors around 2cm deep in a sunny location and be sure to support any taller varieties with sturdy stakes.’
1. Planted too late
Knowing when to plant sunflower seeds is the most important factor in guaranteeing sunflowers bloom. Planting too late is one of the leading causes of sunflowers not flowering, as the plant won’t have enough time to grow and flower before the first frost.
Latest Videos FromIdeal Home
First frosts vary depending on location and weather patterns, but it usually falls between the start of October and the start of November.
‘Sunflowers typically grow and flower within 70 to 100 days after planting,’ says Petar Ivanov, gardening expert from Fantastic Gardeners. Therefore, you should aim to plant sunflower seeds by the end of May at the latest to ensure plenty of time to enjoy the blooms.
2. Not enough sun
It’s no surprise that sunflowers demand plenty of sunlight to bloom, but it may be more than you think.
‘Sunflowers need around six to eight hours of direct sunlight, so one of the causes of sunflowers not flowering could be because they’re in too much shade. Growing sunflowers in a shady spot can produce tall, leafy plants with little to no flowers,’ explains Chris Bonnett, founder of GardeningExpress.co.uk.
Thankfully, there is an easy fix for sunflowers grown in pots – move them to a spot that receives full sun throughout the day.
Unfortunately, this is more difficult with sunflowers in the ground. If the plants are still small, you may be able to relocate them – though you do run the risk of the sunflowers not bouncing back after the move. For more established sunflowers, it may just be a case of remembering to choose a sunny spot when planting your sunflowers out next year.
3. Planted too close together
Linked to the lack of sunlight, planting several sunflowers close together can cause overcrowding and shading, which can lead to sunflowers not flowering.
‘Sunflowers that are planted too close together can begin to compete for sunlight, and this will limit their growth. Tall, single-stem varieties should be placed one to two feet apart, with branching types needing to be further apart,’ advises Richard Barker, horticultural expert and commercial director of LBS Horticulture.
If you have already planted your sunflowers too close together, it may be a good idea to thin them out. While you will get fewer flowers overall, the plants that remain will be healthier and more beautiful.
4. Too much nitrogen
Sunflowers are hungry plants that benefit from regular feeding. However, using the wrong fertiliser can lead to your sunflowers not flowering.
‘Avoid fertilisers that are rich in nitrogen. Nitrogen helps with leaf and stem production in plants, but if a plant receives too much nitrogen, it will push all of its energy into growing tall and producing a lot of foliage, at the expense of flowers,’ says Richard Barker. ‘Try using a fertiliser that does not have as high a level of nitrogen, or a higher level of phosphorus, as this helps with blooming.’
A tomato feed – like Tomatorite, available on Amazon – is a great option for promoting blooms. Feed every week or two during the growing season. You could even try making your own tomato fertiliser.
5. Late bloom variety
Not all sunflowers flower at the start of the season. Some are later-blooming varieties that can flower as late as October.
So for sunflowers not flowering in July and August, it could be that you still have a few months until you see blooms.
‘Check the seed packet before planting to find out the estimated time the plant will take to bloom, and as long as they are receiving the correct care, they should bloom at their predicted time,’ says Richard Barker, horticultural expert and commercial director of LBS Horticulture.
Late flowering varieties include:
6. Not enough water
While sunflowers are quite drought-tolerant plants, the early heatwave this year may have stunted bud formation. ‘Sunflowers develop buds, and in earlier stages of growth, they do need to be watered well. Dry weather during the earlier stages of growth can reduce flowering or at least delay flowering until later, so it’s important to keep moisture consistent until the plants are well established,’ says Morris Hankinson, Managing Director of Hopes Grove Nurseries.
The best watering technique is similar to that for watering roses in hot weather. ‘Aim to water deeply when the soil is dry,’ says Chris Bonnett. ‘Also ensure you have good drainage, as wet soil can also stress the roots.’ Watering little and often is one of the most common watering mistakes and can lead to the plant rotting.
If you have issues with waterlogging, it may be time to improve drainage in your garden.
7. Pests have destoryed the buds
Pests are one of the most challenging reasons your sunflowers are not flowering, as once they’ve damaged the buds, it’s impossible to reverse.
‘If the plants look healthy but the flower buds appear swollen or fail to open, pests may be feeding inside them and leading to the sunflowers not flowering,’ says Jo McGarry, luxury garden design expert at Caragh Nurseries. ‘Sunflower midge larvae can damage developing buds before they bloom. The best way to avoid this is by spreading sowing times to limit impact and choosing hybrid varieties known to cope better with midge damage.’
Other pests like slugs, snails and insects can also damage young plants and destroy developing buds. ‘Protecting young plants from slugs and snails is helpful, and when they are bigger and better established, protection can usually be removed,’ advises Morris Hankinson, Managing Director of Hopes Grove Nurseries.
You could also try companion planting your sunflowers with snail and slug repellent plants.
Starting any flower from seed comes with its challenges, so don’t be disheartened and remember there is always next year.
Read the full article here