Taproot at Home :: Grow Your Own Cosmos

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Grow Your Own Cosmos

by Erin Benzakein

Originally published in Issue 21::WEAVE. 

All winter and early spring, I look forward to the abundance of the summer months, when I can pick fistfuls of blooms....If you have a little bit of time and a sunny garden space, you too can be rewarded all summer long with bouquets to enjoy or give away.

Of all the plant groups, annuals are the simplest, quickest, and most affordable to grow. Annuals are sown in early spring, they bloom mainly in summer, then they set seed and die when the weather cools in autumn. Annuals are the workhorses of the garden—they provide the bulk of our summer flowers here on the farm. 

Of all the annual flowering plants you can grow in your cutting garden (or at the back of your veggie patch), none are more productive than cosmos. They truly are a cut-and-come-again flower—the more you harvest them, the more they bloom—and a single spring planting will produce buckets and buckets of airy, delicate, daisy-like blossoms for many months. You can arrange cut cosmos on their own or weave them into mixed bouquets—the possibilities are endless.

Cosmos are incredibly easy to grow, making them perfect for beginning gardeners. You can start seeds indoors to get a jumpstart on the season, or you can wait and sprinkle them directly outside. Either way, cosmos will bloom in just under 3 months from the date you sow them. To start seeds indoors, sow 4 to 5 weeks before the last spring frost, and then transplant the seedlings to the garden once all danger of frost has passed. Be careful not to start your seedlings too early, or they will quickly outgrow their pots before the weather has warmed enough for transplanting. To direct-seed your cosmos, sprinkle seeds in your garden once all danger of frost has passed. In about a week, you’ll see seedlings sprout up from the soil. Keep the young plants protected from slugs and snails as they are getting established; new growth is quite tender.

Cosmos plants get very bushy and prefer a little extra room to spread out, so space or thin the seedlings to 12 to 18 inches apart. Once in the ground, cosmos will grow rapidly, so be sure to stake them early, while they are still young. Cosmos also benefit from a technique called pinching, which will encourage the already highly productive plants to branch even more vigorously. Here’s how it’s done: when plants are young—8 to 12 inches tall—snip the top 3 to 4 inches off of the plant, just above a set of leaves—with a pair of sharp pruners. This will signal the plant to send up multiple stems from below where the cut was made, resulting in more abundant flower production as well as longer stem length.

I typically do two sowings of cosmos, a month apart, and I always include a good variety of my favorites (see the list below). This gives me loads of blooms and a wide range of flower types for cutting from summer into fall.

  • Double Click Mix A unique double-flowered cosmos, these fluffy blooms are easy to grow and look great in bouquets. This mix includes blossoms in snow white, vibrant cranberry, rosy mauve, and a lovely soft blush. Individual colors are also available.
  • Purity This cheerful, daisy-like bloomer has perfect, pure-white single flowers and produces an abundance of its wildflower-like blooms.
  • Rubenza A dramatic addition to any cutting garden, this uncommon cosmos displays a vibrant range of colors. The large single blooms open with deep ruby petals and then fade into shades of muddy rose and terra-cotta as they age.
  • Seashells Mix This delightful mix is filled with large, showy blooms that have fluted, tubular petals that resemble seashells. Flowers come in a sweet pastel mix of pink, rose, white, carmine, and other unique bicolors.
  • Versailles Mix This early blooming, vigorous mix includes the loveliest blend of daisy-like flowers in white, mauve pink, and burgundy. It’s one of the fastest to bloom from seed (flowering about 2 months after planting) and one of the most prolific mixes on the market.
  • Rosetta This new variety is a must-have for arranging and looks stunning arranged en masse. Blooms have a layer of half-double petals that resemble fluffy petticoats. Rosetta is a mix of soft pink, blush, and rose, and each petal looks like was hand painted.

To prolong their flowering time, harvest cosmos regularly, and deadhead any spent flowers before they set seed. The individual blooms of cosmos don’t last a particularly long time in the vase—about 4 to 6 days—but each stems is loaded with multiple blossoms that open individually over a period of a week. Harvest when the buds are colored but haven’t opened up yet; this will keep insects from pollinating the patch and help stretch their vase life by a few additional days.

Cosmos seed is inexpensive and usually pretty easy to find. If your local nursery or garden center doesn’t carry any, you can order packets online from Johnny’s Selected Seeds, Renee’s Garden, or Floret. For a small investment of time, money, and garden space, you will be able to fill your house with these cheerful flowers all summer long. Happy growing!

  

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