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Deadhead Cosmos
Cosmos will bloom almost continuously throughout summer and up to the first frost if you continue to deadhead it. Take long flower stems back to the ferny foliage below.

What to Deadhead

Although not an exact science, there are a few guidelines:

  • Large flowers, such as those of some pelargoniums, can be snapped off individually. The soft stems of most perennials are easily pinched through.
  • If the tall flowering stems of delphiniums, lupines, and foxgloves (Digitalis) are cut off, new smaller heads might sprout lower down.
  • Dainty plants with small flowers such as lobelias are best trimmed using scissors.
  • For repeat-flowering roses, cut off blooms with pruners at the cluster point, either one by one, or just above a leaf.

Shearing Back

An easy way to deadhead some plants is to trim them back with shears. Trim after flowering for more flowers, fresh foliage, or both. Try this with border campanulas, catmint (Nepeta), hardy geraniums, knapweeds (Centaurea), border salvias, and pulmonarias.

In early spring, shear back growth of winter-flowering heathers (Erica carnea), ling (Calluna), periwinkles (Vinca), St. John’s-wort (Hypericum calycinum), and ornamental grasses, taking care not to cut into the new shoots. Also shear off old leaves on epimediums in late winter, before they flower. Cosmos will bloom almost continuously throughout summer and up to the first frost if you continue to deadhead it. Take the long flower stems back to the ferny foliage below.

Leave to Seed

Not all plants need deadheading. Some will not produce more flowers, and may develop seedheads if flowers are left in place. These may be very attractive, especially in winter, and the scattered seed could result in a crop of seedlings the next year. Try leaving the flowerheads on the following plants:

  • Achillea
  • Astilbe
  • Clematis like C. tangutica, C. orientalis, and their hybrids
  • Eryngium
  • Ornamental grasses
  • Poppies
  • Sedum
  • Teasel
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2 Comments About this Article

  • Sandra NAPIER
    Don't forget to COLLECT those seeds too. I love seed swapping.

    Posted 12 months ago

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  • Sandra NAPIER
    One of the easiest ways to shear some flowers is with Sheep Shears. If you can find them keep them clean and dry them after use and a little oil to protect from rust never hurts!

    Posted 12 months ago

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