How to sow cosmos seeds (2024)

FAQs

How to sow cosmos seeds? ›

It is best started off in a tray indoors. You can direct sow, but if the soil is cold, it will take an age to germinate. Cosmos germinates most readily at 15-25C and takes about a week at these temperatures. Cosmos seed needs light to germinate, so sow on the surface or cover with vermiculite.

Sow seed in early spring directly into the soil where you want your cosmos to grow, or into small pots or modules filled with free-draining seed compost. If growing in pots, pot on seedlings when they are large enough to handle. Plant out in late April/May after the danger of frost has passed.

If you're new to growing cosmos, you're in for a treat. Cosmos are like zinnias and marigolds—they just give and give and give. These low-maintenance flowers with their lacy leaves come from the daisy family and are super easy to grow from seed. You can literally just sprinkle seeds in your pollinator garden.

Fall Planting: Cosmos may also be direct sown in the fall. The trick is to follow the exact opposite course of action required for spring planting, and scatter your seed after a few hard frosts have passed. This ensures that your seed won't germinate until it's ready next spring.

Cosmos seeds do not require any treatment (eg soaking, stratification) before sowing.

Sow 2 seeds per container or cell by creating a 1-half-inch hole into the soil, in 2 opposite corners. You can use a pencil, dibbler, or even your finger to make a hole.

Planting seeds this way is called direct sowing, and it is an easy process that yields great results. Unlike indoor seed starting, direct sowing involves unpredictable elements: weather, wildlife and insects. Even so, many vegetables, annuals, herbs and perennials sprout easily from seed sown directly into garden soil.

Cosmos are incredibly easy to grow, making them perfect for beginning gardeners. Seeds can be started indoors to get a jump-start on the season or sown directly into garden beds once the weather warms. Either way, cosmos will bloom in just under 3 months from the date you sow them.

Drop one cosmos seed in each cell, covering them with about 3mm of compost, and water-in well. Place the tray into a clear polythene bag and move to a warm place at 15 - 25°C such as a greenhouse or warm window sill.

Can you sprinkle flower seeds on top of soil? ›

If there is no vegetation in the space where you plan on growing wildflowers, your chances of success may be a bit better if you simply toss the seeds onto the ground. However, if you really want to ensure their success, preparing the soil is highly recommended!

you stick vegetable seeds in the soil. However, with wildflower seeds, a lot of them are really small. and they need sunlight to germinate. So you don't actually bury wildflower seeds, you can just sprinkle them on top of the soil.

Pinching out cosmos can be a good idea because it will improve the appearance of the plants and help ensure that they have a full and bushy appearance. What's more, while pinching out won't have this effect on all plants, pinching back the top growth on cosmos can also encourage the plant to produce more blooms.

Cosmos should be seeded indoors in cell trays or 2-inch soil blocks about four weeks before your last frost. Cover the seeds lightly with soil, and place the tray on a heat mat with a humidity dome. Bottom water or mist to keep the soil moist until cotyledons emerge. Seeds germinate best in soil around 70 degrees.

You won't have to water after they are planted, preventing seed movement. Create a mini greenhouse by covering the seed tray with a plastic tray or plastic wrap. This will keep the moisture and warmth inside, and you shouldn't have to water again till after the seeds have germinated.

Most cosmos are annuals and will need to be resown from seed or planted as seedlings each year. Cosmos atrosanguineus, or chocolate cosmos, is the exception – it is a tender perennial. It's ideal for container gardens as the pots can be brought undercover over winter.

Cosmos seeds require light to germinate, so be careful not to cover them too much when planting.

PLANT SPACING:

9-12". Wider spacing creates stronger, thicker stems.