June 3, 2013
Perennials in winter

It is much more natural to leave plants standing into winter — Mother Nature does. Seed heads can be attractive in winter and provide food for birds. Most ornamental grasses are superb in the winter garden.

Many perennials are partially or totally evergreen. These can all be left to provide good winter effect: bergenia, arabis, aubretia, heuchera, thyme. The foliage of yucca and red hot poker are best tied up to protect the crown of the plant.

Cutting back perennials in the fall
What do we cut down and why? The reason for our action is always important.

All perennials, even those with winter foliage, can be cut down in the fall. This certainly presents a neater garden, and allows for the use of protective mulch in areas where snow cover is not dependable.

Plants that harbour fungus spores should certainly have the foliage removed. Remove succulent foliage, such as iris or day lily leaves that rot in winter.

Some plants can benefit by being cut down to almost ground level in the fall of the first year:

  • to encourage the growth of offsets;
  • to perennialize those with a reputation of being short lived.
Winter success depends on good drainage
Good drainage and a thick blanket of snow will see most hardy perennials safely through the winter. Thorough preparation of the soil in beds or borders is essential. The snowcover is beyond our control but good drainage is our responsibility. Many perennials can succumb to winter wet, even those listed as extremely hardy.

Improving the soil of existing beds
Use a winterizing high-potassium formula in the fall and an all-purpose balanced fertilizer in the spring.

Pelletized gypsom is an excellent soil amendment. This is spread evenly over the soil and worked into a depth of 7 to 10 cm. This amendment causes the fine particles of clay to clump together to provide better drainage and improve soil texture.

Compost or composted manure applied in the fall to a depth of 5 to 10 cm improves soil textures, adds required nutrients and provides added winter protection.

Organic mulches (including bark nuggets, shredded bark, cocoa bean shells) applied to a depth of at least 5 cm adds organic content to the soil, stabilizes soil temperatures during winter freezing and thawing, conserves moisture in all seasons, lessens the need for constant weeding and dresses the garden bed.

Preparation of garden beds
Best done in the fall, ready for spring planting

Double digging

  • Dig out a trench a foot or more deep and set aside.
  • Dig and turn over the next foot of soil.
  • Add 15 cm of compost or composted manure and fork under.
  • The soil from the next trench is piled on top of the first.
  • Again, dig the subsoil and add 15 cm of composted manure.
  • Repeat trenching and forking in compost to the width of the bed.
  • To fill the last trench, use the soil that was first set aside.
The resulting well-dug bed should now be at least 15 cm higher than its surroundings and can be increased to 30 cm by the addition of purchased garden soil to achieve an overall cultivated depth of nearly three feet. Well-tilled soil creates good drainage and aeration and as roots penetrate down to the manure or compost, they will find moisture and nutrients in the lowest level.