Cosmos
Fundamental Facts
HARDINESS: Frost tolerant
PREFERRED SOIL pH: Adaptable
PREFERRED SOIL TYPE: Moderately fertile, well-drained
PREFERRED LIGHT: Sun
ATTRIBUTES: Lacy foliage; white, pink, purple, yellow, or red daisylike flowers; for borders or pots
SEASON OF INTEREST: Early summer to fall
FAVORITES: Sonata mix, white and pink flowers; Seashells mix; fiery 'Bright Lights', 'Cosmic Orange' for orange and red flowers; yellow sulfur cosmos
QUIRKS: Grows poorly in damp, overly fertile soil
GOOD NEIGHBORS: Cleome, purple cone-flower, gomphrena, salvia, zinnia
WHERE IT GROWS BEST: Sunny, modestly fertile, well-drained soil
POTENTIAL PROBLEMS: Stem or root rot in wet soil; beetles
CRITTER RESISTANCE: Good
SOURCE: Seeds
DIMENSIONS: 2-4 ft (0.6-1.2 m) tall, 1 ft (0.3 m) wide
Cosmos in the Landscape
When you want vivid garden color without a lot of fuss, look no further than cosmos. Native to Mexico, cosmos are an American success story, perfectly suited to lean soils and fluctuating weather. These plants have the airy look of a wildflower, standing 2-4 ft (0.6-1.2 m) tall and producing a bevy of white, pink, magenta, red, burgundy, bright yellow, or red-orange daisy-shaped flowers, each with a yellow center. Below the flowers, the leaves are lacy and finely cut, making them a perfect accent for blossoms that linger for weeks.
Even a small garden patch devoted to cosmos is a beautiful sight, especially when courted by butterflies. Intersperse tall varieties with other tall annuals or perennials in beds, or grow midsized cosmos in containers or in gaps in beds where you need a quick flower to fill in empty space. Some of the tall varieties may need staking, or you can grow them in close company I with staff upright flowers such as cleome or tall zinnias, whose stems will keep the cosmos propped up. Compact and dwarf varieties require almost no maintenance beyond clipping off the spent blossoms.
A Cosmos of a Different Color
The most popular cosmos is Cosmos bipinnatus, often called garden cosmos. This species adapts to cool weather and blooms in white, red, and many shades of pink. The 2 ft (0.6 m) tall Sonata multicolored mix is tremendously versatile. 'Candy Stripes' is taller with white flowers edged in crimson, while Seashells mix has unique rolled petals, also in a range of light pink to red shades. A different species of cosmos (Gsulphureus), often called sulfur cosmos, blooms in bright yellow, orange, red, and bicolors.The varieties 'Bright Lights', 'Cosmic Orange', and 'LemonTwist' have a better appetite for hot weather than garden cosmos do.
Increasing the Bounty
To grow either type of cosmos as a wildflower, simply mix the contents of a packet of seeds with an equal amount of sand and broadcast them, scooping up handfuls of the mixture and tossing it with a broad, sweeping gesture onto cultivated, weed-free soil. For more organized plantings, simply sow die seeds in a sunny garden site with well-drained soil, right where you want them to grow, barely covering with soil. Garden cosmos will germinate in cool soil, so you can sow seeds around the time of your last spring frost. Plant sulfur cosmos a few weeks later, after the soil has had a chance to warm up.
Growing Cosmos
Cosmos benefit from soil that is loamy and deeply dug, but they need little, if any, fertilizer, even in poor soil. Dry conditions promote strong growth, and too much moisture can lead to root and stem rot. To prevent these and other diseases, it is wise to rotate cosmos by planting them in a different location every season.
If you find chewed flowers, hand-pick beetles in the morning when they are sluggish, or spray an insecticide labeled for cosmos containing the botanical insecticide pyrethrum.