Skip to content

Get Growing: Sure you can start sunflowers indoors, but their rapid growth means you don't have to

Sunflowers grow extremely fast, they also develop very deep roots.
james bio photo
James Lissy (courtesy photo)

Question: When is the best time to start sunflower seeds indoors?

Answer: This is a great question and thank you for sending this question in, the simple answer is:  Whenever you want to.

Before we dive into a more complete answer, let’s take a quick look at sunflowers to see why they’re awesome and why everyone in Longmont should grow sunflowers (yes, even you).

1. Sunflowers are gorgeous, this is just a simple fact of sunflowers, they’re stunning and make for great photos. 

2. Sunflowers mean more food for pollinators. The more flowers we have the happier our pollinators will be. Pollinators are essential for food that you grow so give them as many chemical free flowers as you can.

3. Sunflowers thrive in low water, dry conditions. They develop deep roots and don’t need much water to survive and thrive.

4. Sunflowers help clean the soil. They’ve even been planted after nuclear accidents to help clean up contaminants.

5. You also could use them as a cover crop if you have a field or spot that you’re not using.

6. Sunflower seeds are delicious. Not only for you, but for the birds. Sunflowers attract a wide variety of birds that will very much enjoy the seeds these flowers provide. If you’re lucky, perhaps you’ll be able to snag some seeds for yourself as well.

2021_03_13_LL_get_growing_sunflowers2An extremely happy bee has a party on a red sunflower. By James Lissy / Courtesy photo
Sunflowers are great and we should all grow them. Now back to the original question, when to plant them.

Sunflowers grow extremely fast, they also develop very deep roots. Both of these facts make me hesitant to suggest starting them inside or in pots. I have always started my sunflowers outside, after the first frost, by directly planting the seeds in the ground, wherever I want them to grow. This has always worked out extremely well. The sunflowers grow ridiculously fast, so much so that there’s a noticeable difference from one day to the next in their growth. I’ve been able to grow 10-plus-foot sunflowers this way, without any issues.

Having said that, you can most certainly try starting them inside if you want. You’ll likely have the most success starting them inside about a month before the last frost. This will allow the plants to start growing and hopefully within a month’s time their roots won’t be developed too much and they can be transplanted with ease. Keep in mind that sunflowers grow very fast, if the roots get constricted within a pot, the growth of the entire plant is going to be stunted and it may take a while for it to recover once it has been transplanted.

2021_03_13_LL_get_growing_sunflowers1Sunflowers dancing behind the beans in July 2019. By James Lissy / Courtesy photo
For experiment's sake, my biggest suggestion would be to try planting a few seeds at different intervals, including directly in the ground after the first frost and see what happens and which seeds perform the best. You could start this right now if you wanted. Plant a seed or two now, then a few more in a few weeks, then a few more a few weeks later, etc., until after the last frost, then plant some directly in the ground. If you do this, be sure to label when each one was started so you can keep track. This way you’ll be able to easily pinpoint the best time to start sunflowers and whether starting them inside or outside is the better way to go.

Plant sunflowers directly in the ground after the last frost or experiment with different planting intervals and see what ends up working the best. Whatever you do, grow some sunflowers, they’re cool and I think we all enjoy walking and biking around town spotting all the different sunflowers that everybody grows.

Have a question?

If you have any questions or subjects that you would like me to cover in this column, they can be emailed to with the subject of “Longmont Leader Question.” I will happily answer any questions that you may have, after all this column is for you to benefit from and enjoy.