Taming the Weedy Monster – How to Renovate a Perennial Bed

perennial borderWhen I travel around visiting clients in the spring, the #1 problem everybody has (next to mud and drainage issues) is the perennial garden run rampant.  The client usually says something like “it started out so pretty, and then we got busy and couldn’t keep up with the weeding and now it’s a wild mess.”  If you can relate, know that you’re not alone and that you have some choices moving forward.

One quick word about new gardensthe best cure is prevention, so if you’re planning a new garden be sure that:

  • perennial weeds are removed before planting;
  • the soil is amended with compost cooked to at least 160 ° to kill weed seeds (we use Moo Doo © because it’s our local product but there are many good choices throughout New England);
  • plants are selected that
    • form dense cover of the ground surface (such as Geranium ‘Rozanne’ or Phlox stolonifera) and that
    • don’t have abundantly fertile seeds or adventurous rhizomatous roots (beebalm, artemisia and all those other neighbor gifts);
  • a 2-3″ thick layer of a local organic mulch is applied; and finally
  • a weeding strategy is implemented – there is no such thing as a no-maintenance mixed perennial border, so be realistic about the cost either of your own time or of hiring a professional.  Early spring is key because there is more light on the ground surface while the perennials are small and weed competition is fierce – so make many dates with your Japanese Hori weeding knife on weekends.  Then plan on being in the garden at least one weekend a month during the summer season and be sure to deadhead your more enthusiastic perennials before they go to seed.
overgrown perennial bed

I think there’s a Rose in there Somewhere…

Back to the Wild Mess of your existing garden –  what should you do if life just had more pressing priorities for you and the damage is done? I have a bed like this, and to my embarrassment it’s the border bed along the road frontage of our property.  It was also the first bed we put in when we moved here 12 years ago.  The border used to be my pride and joy – full of 6′ high Delphiniums that would literally stop cars – and carefully orchestrated to continue blooming right through August.  Then I had kids.  The witchgrass spread, and so did the horsetail, the short-lived Delphinium died out and the survivors spread and choked out their more delicate cousins.  I can’t bear weed-wacking between the shrubs for another season as an emergency weed control strategy, so it’s time to do what really needs to be done – a total renovation.

planting perennialsIt sounds scarier than it is.  One of our landscaping crews of two people can renovate a 50′ x 6′ bed in one day, (or an average of 16-22 sq. ft. of bed per hour per person) but it is heavy work and requires a certain amount of knowledge regarding plant ID and knowing each species’ requirements and quirks.  One good source if you want to learn is fellow-Vermonter Gordon Hayward’s book Tending Your Garden – A Year-Round Guide to Garden maintenance.  His garden in Southern Vermont is gorgeous and I’ve enjoyed reading several of his other books as well.

A note on timing – do the site assessment in the summer or fall if possible, the design work in winter and then be ready to renovate and replant in spring.  Here’s the process whether you do it yourself or you opt to have a pro help:

  1. Evaluate the site – sun/shade, wet/dry, wind, views etc.  Gather a soil sample and have it analyzed. (UVM’s soil lab is a great local resource – it’s only $14 for a basic fertility test and you can just drop it off a Jeffords Hall.  If UVM isn’t close to you then check out your own local Extension Service).
  2. Discuss what has worked, and what hasn’t, and why – how much time is available for maintenance?
  3. Assess the weeds on site – dig a test patch and see if rhizomes have invaded plants beyond repair
  4. Decide which plants will be kept, the numbers and sizes of clumps, and condition
  5. Measure total square feet of bed to estimate labor and the new design – note how plants will be removed and composted
  6. Make a wish list of new plants
  7. Draw a new plan of the bed  – orchestrating the design so that old and new combine to create a full season of bloom, texture, height, repeating elements, winter interest etc.
  8. Early Spring – pick a cloudy cool day when new growth is just emerging – collect your tools and have new plants and soil amendments on hand.
  9. Lay a large tarp along the edge of the border to protect the grass and lift all the plants out onto it with a digging fork and spade.  If the garden is larger than one day’s work (300 SF) then tackle it in sections or have flats and pots on hand to transplant into, and place them in the shade and keep them watered.  As plants are lifted remove any suspicious roots that have become intertwined in the root ball – if it’s infested then toss it, better safe than sorry.
  10. Once all the plants are out, and the plants to be composted are put into the wagon and hauled away, you can lay damp burlap over the freshly dug “keepers” on the tarp.
  11. Next the bed needs to be forked and all weed rootlets sifted out of the soil.  This is where the job can eat time – more weed roots, more time.  The weeded bed is raked and amendments are applied based on the soil test results.  For most gardens we use organic compost and North Country Organics “Pro-Start”.
  12. The keepers are then divided as necessary and relaid according to the new design.  The new plants are laid out as well and then everything is planted.
  13. Finish with a good layer of mulch and water everything deeply.

peonies iris and geranium in VT borderThe results of a garden renovation are usually well worth the trouble and will reduce your maintenance.  Expect to see the transplanted perennials shock a bit for about a week.  Also, some plants such as peonies and iris are usually divided in fall not spring, but you can divide them in spring, they will just sleep for a summer before blooming again.  One product we use to help plants thrive after a renovation is Bio-Magic – it contains a natural rooting hormone and also helps with transplant shock.  Once your plants are done adjusting to the drama, they will reward you once again with fabulous blooms and maybe even garner an encouraging honk or wave from neighbors.