Cosmos are among my favorite summer flowers. The plants’ light, wispy, foliage, reminiscent of dill, is topped by colorful, daisy-like flowers that sway in the breeze. Popular cottage garden picks, I tend to plant cosmos in my raised beds because they attract bees and butterflies. Growing these semi annuals from seed is super easy. In this article, I’m going to share some tips on seeding cosmos indoors so you’ll have seedlings for planting season, as well as how to direct-sow seeds right in the garden.

I find cosmos to be one of those plants that don’t look all that great at the garden center. You don’t usually find them in bloom, so unless you recognize that feathery foliage, you may walk right on by. It’s easy to start plants from seed and you’re in control of which varieties you choose.

Cosmos flowers are native to Mexico, with the range extending into some. There are about 20 known species to choose from, with a range of varieties. “Cosmos” is the common name and the genus, which makes it easy when you’re looking at seed packets and plant tags.

Seeding cosmos indoors

Order your cosmos seeds when you place your veggie garden seed orders. Cosmos plants aren’t particularly fussy, so if you start them indoors, seedlings can easily be transplanted to the garden. Don’t plant seeds too early, you’ll develop very long, leggy plants. Instead, wait four to five weeks before your last frost date. For me that’s about early April.

In seed trays filled with soilless mix, plant seeds about a quarter of an inch (about a half a centimeter) deep.

Types of cosmos .

Cosmos flowers are with the range extending into some . There are about 20 known species to choose from, with a range of varieties. “Cosmos” is the common name and the genus, which makes it easy when you’re looking at seed packets and plant tags.

Cosmos bipinnatus is probably the most common species you’ll find growing in the annuals section at garden centers. ‘Picotee’ is a popular C. bipinnatus variety. My favorite seed blend is ‘Dancing Petticoats’ from Renee’s Garden, which includes ‘Sea Shells’, ‘Psyche’, and ‘Versailles’. There is also a yellow and orange species called Cosmos sulphureus, and Chocolate cosmos (Cosmos atrosanguineus), which is a tuberous perennial.

There are also different petal types to choose from. There are tubular, frilly, and flat petals with various shapes.

Planting cosmos seedlings outside

Even though they are annuals, cosmos still need to be off before planting them in the garden. Wait until all of frost has passed, then choose a well-draining spot in the garden that gets full sun (a little partial shade is okay, too). It’s worth noting that you don’t have to amend your soil with compost like you do with other flowers and veggies. This may help encourage more blooms. And you don’t really need fertilizers either. Too much nitrogen in the soil will just result in more leaves.

Also, be mindful of the heights that cosmos plants reach. Cosmos bipinnatus can grow to be about three feet. That means you don’t want them shading out other plants in your garden. And because of the towering heights of cosmos, compared to other plants, they don’t do that well in pots either.

Seeding cosmos in the garden

For direct-sowing cosmos seeds, follow the advice above for choosing the right location in the garden. Your seed packet is also of information, explaining the right conditions, depth, mature size, etc. Wait until after your last frost-free date to plant seeds.

Sow seeds a quarter of an inch (about a half a centimeter) deep. You can stagger your planting to play with plant heights and bloom times. Water well until plants are established.

How to plant climbing nasturtium seeds

Nasturtiums can be direct sown in a garden bed or container when the of frost has passed in mid-spring. The tender plants of frosts so don’t sow the seeds too early. Plant climbing nasturtium seeds a 1/2 inch deep and space them 10 to 12 inches apart at the base of a trellis, fence, or other structure. When growing them up the posts of an obelisk or teepee, plant three seeds at the base of each post, eventually thinning to two seedlings. Once the seeds are sown, water the bed well to encourage germination. Nasturtiums seeds typically sprout in 7 to 10 days.

Caring for nasturtium plants

Climbing nasturtiums are carefree garden annuals and thrive with little fussing. That said there are a few tasks you can do to promote lush, healthy growth:

  1. Train the plants – Initially, I train the young plants vertically by tying them to their supports with soft garden ties or plant clips. This is not necessary if you’re growing them on the ground.
  2. Water – Garden-grown nasturtiums are reasonably but benefit from an watering if there has been no rain for a week or two. Stick your finger into the soil and if it’s dry 2 inches down, water. I like to use a long-handled watering wand. Water container-grown nasturtiums every day or two, depending on the weather. Again, test soil moisture with your finger and water if it’s dry 2 inches down.
  3. Fertilize – I don’t fertilize climbing nasturtium plants that are growing in my garden beds, but I do apply an organic flowering plant fertilizer to container plants every 2 to 3 weeks in summer.
  4. You don’t need to the flowers of climbing nasturtiums, but blooms or seed promotes the of new flowers.
  5. Watch for pests – Aphids are the most common pest of climbing nasturtiums. The tiny, sap-sucking insects often on leaf or flower stems. I don’t mind aphids on my nasturtiums as they provide food for predatory insects like ladybugs and lacewings. If you wish to remove aphids use a jet of water.