I love the delicate blooms of cosmos, but honestly, there are too many to choose from! I grow cosmos mostly in the Circle Garden, with a few more near the vegetable gardens for the pollinators.
This is my personal garden growing guide. I use it to track seed sources, when to start seeds and if I should adjust growing conditions in my own greenhouse and garden. Please don’t consider this professional grower’s advice.
FAVOURITE VARIETIES AND SOURCES
I’m still playing with a combination of cosmos, zinnias and gomphrena in the Circle Garden. I didn’t like Versailles Red blooming at the same time as the purple clematis (The President) and drumstick allium. I did like the pink and purple-fuchsia combination of the gomphrena I tried in 2023 with Capriola cosmos.
So for 2024, I’m gravitating more toward pink cosmos mid-border and will add a deeper pink zinnia towards the centre. Eventually, I might find my favourite colour combo!
Swallowtail Garden Seeds
- Versailles Red (Cosmos bipinnatus) – early blooming, vigorous, stronger stems
- Capriola (Cosmos bipinnatus) – heavy flowering, dwarf (24-30 inches)
- Apollo Pink (Cosmos bipinnatus, hybrid) – new trial 2024, dwarf habit, 4-inch flowers
- Apollo Carmine (Cosmos bipinnatus, hybrid) – new trial 2024, dwarf habit, 4-inch flowers
William Dam Seeds
- Cranberries (Cosmos bipinnatus, Double Click Series) – 31-40 inches
Hawthorn Farm Organic Seeds
- Blush Cupcake – new trial 2024. Fused petals produce a cup-like flower. Tall – 36-48 inches.
| Hardiness | blooms till frost |
| Exposure | full sun to part shade |
| Deer resistant | yes |
| Bloom time & length | Summer to fall, flower in 10-12 weeks, so late start |
| Deadheading, care | cut off spent blooms |
| Water & soil conditions | dry to medium, drought-tolerant |
| Spacing | 12-15 inches |
My own notes:
I’ve grown cosmos in the Triangle Garden in the past (Sensation Mix) and now mostly in the Circle Garden.
Annuals including cosmos and gomphrena in the Circle Garden in early July 2023
For 2024:
- trying shorter varieties
- start later and prune centres while in pots (this will delay flowers)
SEED STARTING
- 6 weeks before frost is around April 8
- Sow 1/4 inch deep, cover lightly
- Use tempered water to maintain temperature
- Germinates 7 to 21 days at 70-80°F / 21-27°C
GROWING CONDITIONS
- grow cooler 64-68°F / 18-20°C day, couple degrees cooler at night
- pinch out the growing tip when there are three pairs of true leaves
- to force flowers, use artificial light. Eleven hours per day once seedlings have emerged. After 2 weeks, keep lights on for 14 hours or more per day.
TRANSPLANTING INTO THE GARDEN
- pinch plant tips again when plants are 18 inches high
- plants may bloom better in poor soil
- very drought-tolerant