Right time for pruning – Shrubs and Trees

By Rock Giguère

Shrubs and trees grow best if you don’t intervene and let them grow naturally.

However, woody plants sometimes require pruning, whether to remove a cumbersome branch, limit their expansion or aerate and densify their branching. Sometimes, an adequate pruning ensures a good harvest of fruits or for the plant’s good health.

Several techniques destined to help plants during their various growth phases are possible. The important thing is to do the right thing at the right time.

Avoid disappointment

Pruning is sometimes a source of disappointment for a tree or shrub owner. The main disappointment is that the woody plant does not flower as expected because its flower buds were cut. We must proceed to size during optimal period to avoid damaging our plant or losing its flowering.

Pruning of shrubs that flower on previous year’s wood:

Some woody plants produce a spring flowering on previous year’s wood, meaning that the flower buds are already present in the spring. Their pruning is done immediately after flowering. Here are some examples:

  • the black chokecherry (Aronia melanocarpa)
  • the daphnia (Daphne)
  • the forsythia (Forsythia)
  • the hydrangea (Hydrangea macrophylla)
  • the honeysuckle (Lonicera)
  • the rhododendron (Rhododendron)
  • the spring-flowering spirea, such as spiraea arguta (Spiraea arguta) and bridal wreath spirea (Spiraea vanhouttei). The Japanese spirea (Spiraea japonica) can be pruned early spring, with summer flowering.
  • the elderberry (Sambucus)
  • the lilac (Syringa)
  • the weigelie (Weigela)

Pruning of shrubs that flower on the year’s wood:

The woody plants that produce their flowering on the year’s wood, or on the new shoots that grow at the beginning of the beautiful season, are pruned in the spring. Here are some examples:

  • the sweet pepperbush (Clethra alnifolia)
  • the smoketree (Cotinus coggygria)
  • the shrubby cinquefoil (Dasiphora fruticosa, Syn. Potentilla fruticosa)
  • the wild hydrangea (Hydrangea arborescens)
  • the panicled hydrangea (Hydrangea paniculata)
  • the hybrid tea rose
  • the floribunda rose (Rosa floribunda)
  • the grandiflora (Rosa grandiflora)
  • the false spirea (Sorbaria sorbifolia)
  • the Japanese spirea (Spiraea japonica)

Tree pruning

The ideal time to prune a tree is during its dormant period, or before the buds break in the spring, because healing begins early. We can also proceed quite late in the fall, but then the healing process will not be completed until winter. It should be avoided in January and February.

Some trees leak a large amount of sap in the spring. Also, it is recommended for these species, to prune in the middle of the summer. Here are some examples:

  • maple trees (Acer)
  • birch trees (Betula)
  • walnut trees (Juglans)
  • willows (Salix)
  • lime trees (Tilia)

Pruning of a fruit tree

We better leave the complex pruning to professionals. An ideal time is in spring before bud break, because at this time we can see the frame of the tree that we have to work with. Branches that intersect and injure each other are removed, dead or damaged branches are trimmed, and height and width are reduced if desired. Light and regular pruning is better for a fruit tree than harsh and occasional pruning that is often made necessary after a lack of rigour.