Do cosmos plants come back every year or do you need to grow or purchase new plants? Let’s have a look and find out.
Do Cosmos Come Back Every Year?
Almost all varieties of cosmos are annuals and will not come back every year, however, they do regularly self-seed and so a new plant may grow in the same spot next year.
There is also one type of perennial cosmos known as the chocolate cosmos, this plant will come back year after year.
Self Seeding Cosmos
Most cosmos varieties will self-seed quite easily, you just need to make sure you let some of the flowers go to seed.
If you are growing them to use as cut flowers then you will be regularly removing the flowers. Near the middle of autumn, it is a good idea to start leaving some flowers on the plant so they can turn to seed.
Once these flowers have gone dry and brown you can turn them upside down and give them a good shake all over the area where you want your cosmos to flower again next year.
So with this method, while the plant itself will die off you will get new cosmos plants coming back in the same spot next month without you having to do much.
Saving The Seed
Now, this next option is more involved than just letting the plant self seed but does tend to bring better results.
You can let the flowers turn to seed on the plant but instead of scattering them onto the soil you save them and store them in a brown paper envelope.
But this envelope in a dry sheltered spot like a shed over winter and then grow fresh plants from the seed next spring.
This is obviously more involved because you are growing the plants yourself rather than letting them grow wild.
The advantages are that you will be able to start your flowers earlier and will also have a much better chance of being guaranteed cosmos next year.
Self-sown plants can often fail, whether that is due to poor weather that spring or slug attacks doesn’t really matter, you just need to be aware that it can happen.
By growing the plants from seed yourself you eliminate a lot of these risks, particularly if you start them undercover in something like a greenhouse.
Perennial cosmos Cosmos atrosanguineus more commonly known as chocolate cosmos is a perennial form of the cosmos flower.
Now this will come back every year, but that doesn’t mean it doesn’t need a lot of care and attention to do. In fact, it can be harder to get a yearly display out of chocolate cosmos than it is with the annual type.
The reason for this is that it is an exotic flower that likes it hot and doesn’t like the cold. If left alone for a full British winter it will almost certainly die off, it needs looking after.
With it being a tuberous plant it can be treated in the same way as you would a dahlia, lift and store the tuber over winter before planting out again the following spring once the risk of frost has passed.