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One of my favorite additions to the garden is the sunflower. But sometimes, starting sunflower seeds doesn’t always yield the strong seedlings that I’m looking for. Sometimes the seedlings become leggy. If you’re reading this article now, then that’s probably happened to yours too.
So, what can we do about it?
To fix leggy sunflower seedlings, try moving them into more sunlight, brushing over them to strengthen their stems, turning down the heat mats to keep them from getting too hot, and staking them if they need some extra support.
I’ll go over all of these fixes in detail and also go over what might be causing your sunflower seedlings to turn leggy in the first place. Leggy seedlings are still viable! So, I’ll also go over the best method for transplanting them into the garden.
What do leggy seedlings look like?
Sunflower seeds that have gone leggy will look tall but skinny. Leggy seedlings will also have very few leaves and weak stems.
Although we all want our plants to get tall as quickly as possible, sometimes this isn’t necessarily a good thing. Sunflower seedlings that have gone leggy run the risk of becoming too heavy as they mature.
Because their stems are weaker, they can’t support the weight of the large flower head and will begin to flop over. Even worse, the stem can snap completely and kill your sunflowers.
What causes leggy sunflower seedlings?
Sometimes sunflowers can be a little finicky and even though you think you’ve given them everything they need to thrive, they’re still not completely happy. Here are some reasons your sunflower seedlings may be leggy.
Not enough light
Sunflowers need a lot of sunlight to grow, about 8 hours of full sun a day. Hence the name SUNflower. When your seedlings aren’t getting enough light, they will begin to grow and stretch to try and find more.
If you’ve ever grown plants in a window and have noticed that they sort of bend towards the window, it’s because they’re trying to reach more light!
Sometimes when we fertilize our plants, we tend to overdo it. This can especially be the case with nitrogen.
When your seedlings are getting too much fertilizer or too many nutrients, they can grow very rapidly in a short period of time. This is what leads to leggy seedlings.
When starting seeds indoors, you likely won’t even need to apply fertilizer if you’re using a quality potting mix. Once you’re ready to move your seeds outdoors, it’s best to have a soil test done first to see if your soil actually needs any amendments at all.
Too much heat
Similarly to excess nutrients, too much heat can also cause your seedlings to grow very rapidly in a short period of time.
This is especially common if you start your seedlings on heat mats. Heat mats can be extremely beneficial for starting seedlings indoors but sometimes we can get a bit overzealous with them. Grow lights can produce heat too, so all this combined can have an impact on your sunflower seedlings’ health.
Once your sunflowers reach maturity and have stronger stems, the outside heat won’t continue to make them leggy. Temperature is just something to pay attention to in the beginning stages of your sunflower’s life.
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How to fix leggy sunflower seedlings
To give your sunflowers their best shot at life, it’s better to treat legginess sooner rather than later. Here are the best ways to treat legginess.
Move seedlings into more light
If your sunflower seedlings are leggy, the first thing you want to do is to move them into more light. If your seedlings are still inside, then legginess is a sign that they’re ready to be planted outside.
Because sunflowers require a decent amount of sunlight to grow, they’re not the best option for an indoor plant. If you don’t want to plant them directly into the ground, then plant them into a container and leave them on a porch if you have one.
If the weather is still too cold to put your seedlings outside then it’s best to invest in some grow lights to make sure your seedlings have plenty of light.
If you’re unfamiliar with grow lights and not sure where to start, we have a couple of great articles to help get you going:
Turn off the heat mats
As I mentioned before, high temperatures can also cause legginess in your sunflowers. If you have your starts on grow mats and they look pretty leggy then the best thing to do is to turn the temperature down or to turn them off completely.
If you seeded your sunflowers directly into the garden, then there’s not much that can be done to change the temperature outside. But, making sure the sunflowers stay watered will help to keep the roots cool. Mulching will also help in keeping the soil cool.
If, after transplanting your sunflower seedlings outside, they still seem a bit leggy and need some extra support, then try staking them.
Similar to how we stake tomatoes to support them, the same can be done for sunflowers. This method works best once your sunflowers have gotten a little bit of height to them.
Once they’ve reached about 1 foot in height, you can go ahead and stake them. You can use wood stakes, T-posts, or pretty much any tall sturdy thing you might have laying around to support your sunflowers.
Use string or twine to attach the stem of the sunflower to your stake and continue to add string as the sunflower gets taller.
This one may sound a little silly, but passing or brushing over your young seedlings with your hands can help to strengthen their stems.
Think of it like a plant workout. Passing your hand gently over the tops of the seedlings is forcing them to fall over and get back in their upright position, thus strengthening their stems. It’s almost like they’re doing a situp.
With this method, you don’t need to brush them too hard. Just a gentle pass with the hand so that they pop right back up is enough.
Some people also like to use a fan set on low to mimic this process too instead of using their hands. The fan mimics the wind that your seedlings will be exposed to once they’re moved outside.
If you do opt for the fan method, you only need to have it on during the day until your seedlings are ready to be planted outside.
This obviously isn’t the ideal situation but if your seedlings are still pretty young, I’d say only a couple of weeks old, then you may want to consider starting over.
When you start new seedlings, try to change some of the conditions that may have caused your last batch to go leggy. For example, make sure they have some more light than your previous seeds or that the heat mats aren’t turned up too high.
If your seeds were started outside, hold back on the fertilizer and make sure your seedlings are getting ample water to help them stay cool and hydrated.
This should yield you some much stronger sunflower seedlings.
How to plant leggy sunflower seedlings
Don’t let your leggy seedlings scare you. There is still plenty you can do to help your sunflowers out and turn them into the big and beautiful sunnies that you’re looking for.
You can plant leggy sunflower seedlings as you would pretty much any other kind of seedling. But with your leggy seedlings, try to plant the stem a little deeper than you would a normal seedling.
This will give your sunflowers a little extra support until they strengthen their stems a bit and keep them from being knocked over by any rain or winds.
As I said before, If the weather is still too cold to put your seedlings outside then pot them up into a bigger container and get them under some grow lights. You can bury the stem deeper in this case as well.
Sunflowers are a fan favorite in most gardens but can lead to disappointment when they droop or fall over from weakened stems. To recap, here’s what you need to do to help your sunflowers overcome legginess and give them their best shot at thriving:
- Make sure your seedlings are getting enough sunlight and move them into a better location if not.
- If using heat mats, turn them down to the lowest setting or off completely. For seedlings that are outside, make sure they have enough water to help keep their roots cool.
- Brush over your seedlings with your hands or with a fan to help strengthen their stems.
- Stake young sunflowers that are beginning to droop to give them some extra support.
- If it’s still earlier enough in the season, don’t be afraid to plant a fresh batch of seedlings and start over.
Check out these must-have gardening products
You don’t need much to start gardening, but some tools and products will make a difference in how comfortable and effective gardening can be for you. Here are my favorites:
- Garden Trowel. A good garden trowel will last you many years. I love how sturdy this hand trowel from WOLF-Garten is, the metal doesn’t bend and it has a nice grip.
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- Dutch Hoe. Dutch hoes may seem old-fashioned, but there’s nothing like a quick sweep through the topsoil to get rid of small weeds – no bending required. I love WOLF-Garten’s selection: this dutch hoe coupled with their universal handle.
- Grow Lights. These grow lights from Mars Hydro are super strong, yet dimmable, so they fit every stage of growth. They don’t put out too much heat and are very economical.
- Seedling Trays. There’s an art to choosing the best size for seedling trays so that it holds the perfect amount of water and gives the roots enough room to grow. These germination plugs are perfect when coupled with 1020 bottom trays.
- Liquid Fertilizer. You’ll need to feed your plants from the seedling stage, all the way to fruiting. This organic fish & seaweed blend is a very versatile option. Use it half-strength for young plants and full-strength for established plants.
Browse our list of tools, fertilizers & pesticides, indoor growing products and seed shop recommendations – we hope you find our selection useful and it saves you some time!