Perennial Garden Maintenance in August

Perennial Garden Maintenance in August

If you grow perennial plants, this is a good week to do a flower garden assessment and some quick fix improvements. Since our fall season is so long on Cape Cod, the clean-up and other maintenance you do in August will result in a more attractive garden for the next two months. Here are some things you can do to make your perennial garden look better right now.

  • Deadhead spent flowers. Cut off dead or wilted flowers, usually by following the stem underneath them down to where it joins the foliage and cutting there. So instead of just cutting off the finished flower on your purple coneflower, for example, cut that flower’s stem down just above where it meets a good growth of foliage. That will look better than just cutting off a flower and leaving a bare, empty stem.
  • Remove the stems of finished daylilies completely by cutting them near the ground. If the daylily has a lot of dead leaves or yellow-streaked foliaged, you can use a shearing tool or hedge trimmer to chop the entire plant down about three inches from the ground. The daylily will put up new, fresh foliage that will look good into the fall.
  • Notice any plants that have powdery mildew on their leaves. Summer phlox and bee balm are the most mildew-prone, but peonies often get mildew at this time of year as well. Cut these plants to the ground and either bury, burn or otherwise destroy the diseased foliage. (Don’t put it in the compost pile.) The bee balm and phlox will grow new foliage that is clean, although they won’t flower again. Peonies will remain dormant until next spring.
  • Pull weeds. Yes, it’s sad but true. Weeds have sprouted and grown in July and August. The heat-loving plants such as purslane, spotted spurge and carpet weed can be found in most perennial gardens right now. These can either be hand pulled or cut off using a hoe. The hoe is a great tool for those who don’t want to bend down or get on their hands and knees. Smaller types make it easy to work around clumps of perennials.
  • Transplant. It’s a fine time to move perennials from one spot to another. This is especially true of any plant that has bloomed earlier in the spring or summer and is now past its flowering period. Dig a new hole for the plant first, making it larger than you’ll probably need. Scatter some Bio-tone fertilizer in the hole. Then dig out as much of the root system as you can and place the perennial in the hole, filling it in with native soil. Water the plant in well, then top-dress the area around the plant with compost or composted manure. You can either add an inch or two of mulch over that compost now or wait to mulch in the spring. Be sure to water recently transplanted perennials deeply once a week into October.
  • Fill bare spaces. If you’ve got places in the garden where you’ve removed plants, or things have died, it’s a fine time to fill those spots with either a new perennial, some flowering annuals, or even a container that contains an attractive plant. Some people move a bird bath into an empty space or use a garden ornament to attract the eye. If you’ve got a large area that is suddenly in need of filling, consider placing a colorful bench there while you decide what other plants would be best long-term.

    If your daylily looks like this in mid-August, cut it to the ground and it will produce new, fresh leaves.


    See the low weeds between the Profusion Zinnias (annuals) and the perennials? There are baby purslane, oxalis,  and spotted spurge in this garden, about to grow bigger. You’ll want to remove such weeds before they produce seeds!

    A hoe will quickly cut these annual weeds from their roots. You can either pick the cut weeds up or rake them out of the garden.

    This area looks cleaner without the weeds and best of all they were removed before going to seed.


    Don’t cut fall flowering perennials down now! This includes mums, asters (shown here) and Montauk daisies.

    Part of August perennial maintenance is placing new plants in the garden. If you’re choosing fall-flowering varieties you’ll enjoy their color this year and for seasons to come.

    If you want more information about perennial garden care, register in advance for C.L.’s talk on Perennial Garden Maintenance, a Sunday Seminar to be held at Country Garden on September 29th at 1 PM. Call the store for details: 508-775-8703.

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