I was given a tree peony in a container. It even has a couple of buds.
Can I plant it in the ground in spring, or must I wait until fall? How should I prepare the soil for planting?
Expert opinions vary on the importance of waiting until fall
to plant tree peonies, or Paeonia suffruticosa. The Sunset
Western Garden Book (2007) says “All peonies are best
set out in fall”, while The Gardener’s Guide to
Growing Peonies suggests that if peonies are planted
in spring, the gardener must be very careful to water
them well in dry weather that first summer. Of course,
watering will still be an issue if your gift remains in
the pot all summer! Also, this same source says in an excerpt:
Tree peonies usually become available in the early
spring and…have small flowers. While it is very
tempting to allow the plants to flower, this can
considerably weaken a young tree peony. The buds are,
therefore, best removed…and the shoot pruned to leave
three or four leaves… Tree peonies are normally
sold…in pots…with a peat-based compost. This is a
suitable medium for transport, but the plants can
deteriorate if they are not planted out fairly quickly
into normal soil. … In the autumn, it can be dug
up…and planted correctly in its permanent home.
I don’t know about you, but I wouldn’t be willing to
nip off those little buds! The “heeling in” practice, which
involves planting the peony temporarily, might work though.
Organic Gardening magazine published an article on this
subject, from which you can read an excerpt:
To heel them in, choose a sheltered, shady site and dig a V-shaped
trench. Make the trench wide and deep enough to accommodate the plants’
roots and long enough to prevent crowding. Place the plants in the trench
at an angle, making sure the roots are below ground level. Refill the
trench with soil (don’t pack it down) and water the plants thoroughly.
Check the soil moisture occasionally and water as needed. “You can leave
plants heeled in for months, but I would suggest holding them that way
only for a few weeks,” says Amy Grotta, extension faculty in forestry
education at Washington State University. “You don’t want them to break
dormancy before planting.” Plants that come out of dormancy early are
susceptible to frost damage, so plant as soon as possible to prevent
harming your new purchases.
Directions for preparing the soil are very consistent
in different literature: your tree peony will need a
sunny site with rich soil, and “Tree peonies benefit
from the application of a heavy layer of
compost–particularly if they are grown in sandy soil”
(says Martin Page in The Gardener’s Guide to Growing
Peonies). At least several days before planting, you
should dig a hole at least one foot in diameter, and up
to 3 feet in diameter, and amend the soil as needed in
that planting hole. Unlike herbaceous peonies, tree
peonies are planted 6 inches deep (that is, with the
graft union 6 inches deep).