Cosmos are known for being tall and taking up a decent amount of space in the garden, which may have led you to believe they can’t be grown in pots or containers. Not so fast! There are dozens of cosmos varieties, and of those, many have a compact growing habit, which comes in handy when you have a container garden and want to have the cottage charm of cosmos.
Cosmos can be grown in pots with one plant per gallon container. Use a potting soil mix without fertilizer, and choose dwarf or compact varieties such as the Apollo or Sonata series. These cosmos varieties reach about two feet tall and make excellent cut flowers, even when grown in pots.
Growing cosmos in pots isn’t difficult, and with the list of recommended varieties in this article, you’ll be able to order seeds (check out my post on high-quality online seed companies) and get started growing them right away.
Do cosmos grow well in pots?
Cosmos can grow well in pots as long as the plant has enough space. One gallon per plant is sufficient, and the larger the container, the more cosmos you can grow. For example, a three-gallon pot or container can hold three plants. Shorter varieties are better suited to growing in pots.
Cosmos don’t like very rich soil, whether grown in the ground or containers. Too much fertilizer will result in tall, weak stems that don’t produce many flowers. To avoid this, use potting soil that doesn’t have added fertilizer, or make your own potting mix.
Cosmos potting mix:
Potting mix is simple to make with a recipe of peat moss or soil, compost, and perlite or vermiculite. The peat moss or soil provides some bulk to the mix. Use whichever medium is available to you. You can even use coco coir instead of peat moss. It is less acidic and more environmentally friendly, though it is more expensive than peat moss.
Use bagged compost or worm castings to add organic matter to the potting mix. It will also provide some nutrients for the cosmos without overdoing the fertilization.
Perlite prevents compaction of the soil mix, and vermiculite retains moisture. Use one or the other, or a combination of the two depending on what’s available. Perlite is sometimes easier to find than vermiculite and a little cheaper, too.
To make the mix, combine the ingredients:
- 1/3 soil or peat moss
- 1/3 compost or worm castings
- 1/3 perlite or vermiculite (or a mix of both)
It doesn’t matter what size your “scoop” is, as long as you maintain the ratio. Mix the ingredients thoroughly and wet it so that it’s moist but not saturated.
How to grow cosmos in pots
Growing cosmos in pots is easy and similar to growing them in the ground. Choose a pot or container that’s at least one gallon and fill it with the soil mix you made or a store-bought potting soil. Make sure to use a pot with drainage holes so excess water can drain out and not sit in the pot.
Once the pot is full of soil, either sow seeds directly in the pot or transplant seedlings. If it’s early in spring, seeds are the better option. You can find so many more varieties from seed companies than you can when you purchase seedlings at the garden center or nursery.
To direct sow seeds in the pot, scatter a few seeds (depending on the size of your container) on the soil’s surface, then cover with a quarter-inch of soil and water. For more details on sowing cosmos, check out this post, Easy Steps To Plant Cosmos Seeds, Indoors And Out.
However, if it’s already midsummer, buy seedlings so there’s time for your cosmos to bloom before the end of the growing season since cosmos are a warm-season annual. You might only find tall varieties at the nursery, but as long as you give them some support, they’ll do fine a garden pot.
As the cosmos grow, give them one deep watering per week. If you’ve planted them in a terracotta pot, check the moisture more frequently since terracotta dries out faster than a ceramic or resin pot.
Recommended cosmos varieties for growing in pots or containers
Dwarf cosmos and smaller-growing varieties are best suited for growing in pots. Their compact size and height ensure the plant’s roots have enough room in the container. Fortunately, there are plenty to choose from. Swallowtail Garden Seeds has a great selection of shorter cosmos varieties.
Standard varieties that reach around four feet tall can be grown in pots, too. Just make sure you don’t overcrowd the plants. Stick to 1 plant per gallon of pot.
Apollo Series: This line of cosmos plants grows to 18-26 inches tall. The flowers are single, meaning they have one row of petals, but the petals are slightly ruffled, which gives the flower a fuller look.
- Apollo Lovesong: On my list for this year, Lovesong is a mix of white and pink ruffled flowers. Some petals are bicolor, meaning they have both colors on one petal.
- Apollo White: Straight white single flowers with scalloped edges.
- Apollo Pink: Light pink single flowers have fluted petals, similar to the taller Cupcake Mix.
Sonata Series: Reaching 24 inches tall, the Sonata series produces single flowers in single colors. The leaves are prolific and lacy, which provides excellent filler for bouquets. Set your cosmos against the green leaf background, and the blooms will really stand out.
- Sonata Complete Mixture: Get all the colors in one packet with this mix. Carmine, red, white, purple (really, it’s dark red), and pink flowers make everyone happy with their favorite shade.
- Sonata White: A favorite of mine, this all-white flower has a perfect yellow button center and sharp petal edges, similar to the taller Afternoon White variety.
Cosimo Series: At 18-24 inches, this line of cosmos is not only the perfect size for pots, but it also produces excellent cut flowers in just 8-12 weeks. Have a container of these on your patio, and all it takes for a fresh bouquet is stepping outside with a pair of clippers. What a treat
- Cosimo Collarette: Semi-double petals have one row of full petals and a second row of short, whisker-like petals around the center. Flowers are pink and white bi-color.
- Cosimo Purple Red-White: The name says it all! Single flowers have a mixture of red, pink, and white on each petal, with some flowers more red and others more dark pink.
Now that you have your variety picked out make sure any lingering questions about growing cosmos are answered. This post will get you there: Are Cosmos Easy To Grow? Yes, Especially From Seed!