Spring Cleanup – Perennials

(Question)

When is the best time to clean up the yard to prepare for the coming season (it is the end of March)?  I am concerned about weather conditions and new growth.  In particular, I have a variety of perennials – hosta, astilbe, rudbeckia, echinacea.

 

(Answer)

Let the ground defrost and dry (it should crumble in the hand, not stick together in clumps) before any spring cleanup. This avoids soil compacting and makes it easier for the plants/grass to emerge and thrive.

Additional activities to consider include:

  • Remove burlap/protective materials from plants in March (around now!).
  • Once the ground has thawed, top dress with compost.
  • Remove clumps of matted leaves by hand to avoid damaging newly emerging sprouts. If you shredded the leaves in the fall, though, leave the leaf mulch on the beds.
  • Perennials:
    • Evergreen perennials generally do not need to be cut back.
    • Spring-flowering alpine flowers (e.g., pinks, moss phlox) should not be pruned until after they bloom.
    • Semi-evergreen perennials (e.g., Coral Bells, Foamy Bells, Japanese sedge, ferns) – may look the worse-for-wear by spring, go ahead and remove the tattered leaves.
    • Tall flower stems (e.g., shasta daisies, black-eyed susans) will have died back last autumn – go ahead and remove the dead stems.  The plants’ little evergreen rosettes (these will be easy to see early in spring – they are at ground level) should be exposed. You can tidy up and clean dead material from around these newly sprouting leaves.
    • Woody perennials (e.g., artemisia, butterfly bush, lavender, mallows) should be ignored until at least mid-spring, when you can prune them back.  Leave around 15 cm (6 inches) of stem at the base, to allow for new buds to appear.
    • Many perennials simply die back to nothing over the winter (e.g., peonies, day lilies, Solomon’s seal, host) — you can cut these back to ground level.
    • Ornamental grasses can be cut back in early spring, when new growth is starting to appear.
    • Alternatively, some lazy gardeners just leave everything as is and clip the plants later in the season, when their “deficiencies” (i.e., dead bits) are more evident [or not at all!].  While dead/decaying plant material left on plants will provide organic matter for the soil bed, these materials may increase the risk of pests/diseases.
    • Mature perennials and ornamental grasses can usually be divided in mid to late spring, if you wish to do so. (More info on when to divide which plants is in the resources set out below — some plants should not be divided until after blooming).
    • Shrubs should be transplanted in early spring, before leaves emerge.
  • If any your perennials have exposed roots, replant them [this can be an issue with Heuchera (coral bells)].
  • Use soil from last years planters/pots to top dress flowerbeds or add these to your compost pile.
  • Add any cuttings, including material from last year’s annuals, to the compost bin (unless the plants were diseased – e.g., with powdery mildew).
  • Finally….start pulling out weeds in early spring, when they are just starting to emerge – this makes weed control a lot easier as the season progresses.

For more comprehensive information, see the following resources:

As well, the Toronto Botanical Garden’s Spring gardening checklist will help you organize your tasks!