Last updated on December 14th, 2021
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Sunflowers are cultivated for their large blooms and abundant seeds but what happens if your sunflowers don’t bloom?
The good news is that it’s usually something that can be resolved once you identify the issue. In this article, you will discover some of the reasons why your sunflowers are not flowering and what to do about them. Without wasting any more time, let us dive in:
Do your sunflowers get enough sun?
Sunflowers as denoted by their name. They really, really enjoy getting lots of sun, which means planting them in a bright sunny location in your garden. Avoid planting your sunflowers in shaded areas because they should get a minimum of six hours of direct sunlight. Additionally, water your sunflowers to ensure that they do not wilt from their long exposure to the sun.
If you are growing your sunflowers indoors, as many now do with the more miniature varieties, you need to ensure they get direct sunlight once they mature. If you cannot provide natural sunlight, consider using grow lights, these can be easily sourced online.
When to sow sunflowers seeds so they have time to mature and flower
With over forty varieties of sunflowers available, blooming times will differ, with some flowering much earlier than others. After selecting the variety you want, it is important to sow them at the right time so that they can develop without any stressful environmental factors. You don’t want to sow seeds as temperatures drop in the autumn because they might die before they mature.
This is especially important for sunflowers being grown outdoors because it is easy to prevent frost issues indoors. If you are sowing sunflowers, I recommend planting seeds indoors around April-May in 9cm pots and then planting outdoors once they have established a good root system and the risk of frost has passed.
Have you given them enough time?
Sunflowers have a full life cycle of around 125 days so this means they need time to grow, produce buds and flower to make sure you give them enough time. It can take around 65 days from sowing seeds until the buds are even produced and then a further 25 days for them to fully open. With this in mind, if it’s early in the season, give them time to develop properly as their buds seem to form out of nowhere.
What soil type have you planted your sunflowers in?
Sunflowers need nutrients to thrive and without these nutrients, your sunflowers will suffer stunted growth if planted in poor soil. If the soil in your garden is not very fertile, use a slow-release fertiliser or good quality garden compost to ensure the plants are well fed and to give them the best start. Once flowering, feed them every two weeks with a high in potash feed, this will promote better flowering. A good cheap feed to use is actually tomato feed.
Alternatively, grow your sunflowers in pots so that you can use good quality potting compost but they will need feeding and watering more often as they can dry out quickly when grown in pots.
If the leaves on your sunflowers start to turn yellow, read this guide on possible reasons and how to nurture them back to health
Watch out for birds and deer that have a liking for sunflower buds
Your sunflowers might not be blooming due to damaged buds. Physical damage will prevent the buds from getting the nutrients they need to bloom. The damage can be due to curious wildlife such as birds and deers that enjoy eating the buds. To prevent wildlife from eating the buds, erect a physical barrier around the plant using a durable and breathable mesh.
Nitrogen oversaturation can cause plenty of green growth with no to very few flowers
While plants need nitrogen to thrive, too much of it can mean that the sunflowers concentrate on foliage growth rather than buds and flowers. Plants that lack adequate nitrogen will present yellowing leaves and those with too much nitrogen will produce fewer blooms as mentioned. To help prevent nitrogen saturation, avoid overfeeding the sunflowers and once they start producing buds switch to a high in potash feed such as tomato feed.
Use fertilisers as recommended and don’t dispense a large quantity at once. Find a slow-release fertiliser and only feed the sunflowers during the growing season when they need additional nutrients to support blooming.
Also, avoid sowing sunflowers next to legumes. This is because these plants are known to produce nitrogen that accumulates in the soil over time. Practise rotational cultivation to allow the soil to dispense the excess nitrogen.
Are pests causing a lack of flowers on your sunflowers?
Pests can cause irreparable damage, especially in large numbers. Various pests affect sunflowers including thrips, weevils, spider mites, aphids and sunflower moths. Usually, infestations start on the foliage and then spread to the stems and buds. Luckily, these infestations do not go unnoticed and you can catch them before they do too much damage.
Look for signs of pest attacks on the plant and note any other unusual activity. After identifying the culprit, use natural predators or pesticides to kill the pests. Most standard pesticides will treat most common plants. Just make sure you use a fruit and vegetable-friendly pesticide if you intend to eat them.
If also worth noting that some sunflowers just produce one large flower and if the end of the stem is damaged by pests, wind, etc, this could also be the reason you don’t get any flowers.
Lets wrap this up
While it might be concerning to see your sunflowers not bloom, you can undertake different measures to prevent the issue from recurring though it’s not always possible to encourage flowering if it’s too late in the season. Once you solve the issues, you can enjoy the sight of thriving blooms.
Overall, you have learned that sunflowers not flowering can be fixed and that there is always a reason, whether it be something as simple as not getting enough sun.
Simply ensure the plants get enough water and nutrients, expose them to adequate sunlight, the more the better for sunflowers. Use fertilisers appropriately, remember don’t overdo it trying to grow the tallest sunflowers only to be disappointed by the lack of flowers. For most people, all you need to do is plant them in full sun in well-drained fertile soil. Feed with high in potash feed once they produce buds and keep them well watered being careful not to overwater and you should grow amazing sunflowers.
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