How to Grow Cosmos
If you are a new gardener, Cosmos are a great plant to start with. Fast growing, there is little that can go wrong with this tall growing plant. Cosmos are native to Central America and Mexico. They grow quickly to a height of 4-5 feet. Brightly colored single or double flowers include white, pink, orange,yellow, and scarlet.
Cosmos look great at the back of the garden and in informal arrangements.
Cosmos are grown from large seeds, making them easy to plant. They germinate quickly and never stop from there, normally growing four to five feet in a season.
Sow directly into the garden just before the last frost in your area. Space plants 12 inches apart and thin to 18 inches.
While most Cosmos are annuals, there are perennial varieties. Perennial varieties are Rhizomes and can also be propagated by division.
How to Grow:
Cosmos prefer full sun to partial shade. They will do well in both average and poor soils. They are tolerant dry soil conditions. Add a general purpose fertilizer once or twice a season.
Taller plants mayrequire staking. However, this can be avoided if planted in an area protected from the wind.
Insect and Disease:
Insects and disease problems are very rare for Cosmos. If problems occur, treat early with organic or chemical insect repellents and fungicide.
STEP 1: Check out your local garden center in spring for cosmos seeds and seedlings. Because they’re so fast and easy to grow from seed, however, many nurseries don’t carry them as seedlings.
STEP 2: Choose either Cosmos bipinnatus, which has feathery foliage and large daisy-like flowers in all the ranges of white, pink and red, or Cosmos sulphureus, which has smallerflowers in more brilliant, sunset hues and is drought-resistant. (Cosmos also reseed easily.)
STEP 3: Plant indoors four to six weeks before your region’s average last frost date to get earliest bloom. Otherwise, plant outdoors directly in the soil after the last frost date, 8 inches apart in full sun in average soil.
STEP 4: Trim spent blooms to encourage a longer bloom period.
STEP 5: Pull out plants, and discard in fall once frost kills them.
- Cosmos require moderate to little water.
- Plant cosmos in groups of at least a dozen to take advantage of their wildflower-like effect.
- Cosmos don’t thrive in overly rich soil. They’ll produce lots of tall foliage but fewer flowers.