Paeonia rockii.

Gardening: Don’t overlook tree peonies

‘Not as attractive as their herbaceous cousins.’

  • Sun Jun 11th, 2017 6:00am
  • Life

The first question most people ask when confronted with the choice of purchasing a tree peony as opposed to the regular garden variety is, what’s the difference between the two?

The simple answer is that regular peonies (Paeonia lactiflora) are herbaceous in nature – dying back to the ground each winter – while tree peonies (Paeonia suffruticosa) eventually develop a woody above-ground framework that becomes a shrub with age.

Another significant distinction is the actual flower size, with the tree peony having fewer blossoms, but much larger terminal blooms, with these being up to 10” across with a broader colour range.

The other difference most gardeners notice right off is the higher price tag, but tree peonies are all grafted and most imported from Asia, so the production and shipping costs are reflected in the purchase price.

Many people overlook them at their local garden centres simply because they are not as attractive as their herbaceous cousins, as it takes three to four years for tree peonies to mature into an impressive display, after which no one regrets that investment of time.

When planting, you want to choose a site with morning or late afternoon sun, as a midday exposure will often scorch the silky flower petals. Of equal importance is shelter from prevailing winds and adequate drainage, as wet soils will cause the roots to rot.

Dig a hole large enough to be able to have the graft between 4-6” below ground level (which is much deeper than your traditional peonies) and amend your backfill with compost or sea soil.

You might also want to blend in a few handfuls of dolomite lime as tree peonies prefer a neutral or slightly alkaline pH and our soils tend to be acidic.

Water deeply, but infrequently, waiting until the top few inches of soil have dried, as too much irrigation may cause your young tree peony to fail.

In early spring, you will need to topdress with an inch of well-rotted manure or compost, and prune out any dead or broken branches at this time.

Tree peonies cannot be divided to make new plants and really hate root disturbance, so choose your original planting site carefully and try not to move them around.

These shrubs are quite hardy at USDA Zone 4, but gardeners in the Interior may want to mulch the crowns of their tree peonies to protect them during winter, and be patient in spring as tree peonies flush their leaves late and are often discarded prematurely.

As previously mentioned, the colour range of these plants surpasses that of the mundane rose, pink and whites of traditional peonies – with true deep reds (‘Houki’), orange (‘Kinkaku’), bright yellow (‘Kinshi’), maroon (‘Koukamon’), striped reddish-purple and white (‘Shima-Nishiki’) and true purple (‘Shimadaijin’), all being readily available in spring.

If fact, many garden centres only offer tree peonies by colour as opposed to cultivar, but if you look carefully there is usually a small band stapled around the stem that will indicate the variety.

There are even a few rare species tree peonies that can be found locally from time to time. These include the Tibetan tree peony or Paeonia lutea var. ludlowii, which can grow up to 8’ tall here and bears 4” wide bright yellow blooms.

The always impressive Paeonia rockii produces large semi-double white to pale pink blooms with dark purple blotches, which are strongly fragrant. Although the flowers are smaller at 3”across, the unique dark burgundy colouring of Paeonia delavayi flowers make them an interesting addition to any plant collector’s garden.

Mike Lascelle is a local

nursery manager and

gardening author