The following information will acquaint you with the appropriate times and
best methods of transplanting popular perennials. Most perennials grow larger
every year, usually by spreading through underground stems or roots, and may
need to be divided after 3 or 4 years. When flowers become sparse and smaller,
it often indicates that the perennial needs to be divided. The appropriate time
to divide perennials really depends on each plant. However, a general rule of
them is to divide spring and summer blooming perennials in late summer or fall
and to divide fall blooming perennials in early spring.
METHOD OF DIVISION
Dig up a large root ball of the perennial and determine where the stems
originate from the roots. If it is difficult to see the area, hose the soil off
of the root ball with a strong stream of water. Use a sharp knife to cut down
between the stems and through the root ball. Each division should contain
several stems (with numerous roots attached) in order to make a nice showing of
flowers the following year. The old center of the clump, which often doesn't
contain stems can be discarded. Some large clump-growing perennials have very
vigorous root systems. After lifting the clump from the ground, insert two
spading forks, back to back, and pry the clump apart. Tough roots like those of
daylilies and hostas may require a hatchet or saw to further cut the roots
apart.
TRANSPLANTING The new planting hole may need to be amended with
some type of organic matter. Adding one shovelful of peatmoss or compost to
every two shovelfuls of garden soil is recommended. In addition, mix a little
superphosphate fertilizer in the bottom of the planting hole to promote strong
new root growth.
HERE ARE SOME OF THE MOST POPULAR PERENNIALS AND SUGGESTIONS
FOR THEIR DIVISION:
DAYLILIES: Divisions can be made in the spring or
fall. If divided in spring, do it just after the new growth has pushed through
the ground. When divided and replanted properly, they will fill out well but may
not have many blooms the first summer after dividing. Daylilies may need to be
divided every 5-6 years.
IRIS: It is best to divide iris right after
flowering. When dividing, reduce the foliage height by half, cutting the leaves
into a fan shape to conform to their usual appearance. A single fan of leaves
can be planted but to have a nice flowering clump, set three fans in a triangle
10-12 inches apart with the fans facing the same direction. The shoulder (or
top) of the rhizome should be only slightly covered with soil when it is
planted. A well draining soil is very important.
PEONIES: Peonies can
sometimes be left 10-12 years without dividing. They are best divided and
transplanted in the fall. Select divisions with 3-5 eyes (the pink buds on top
of the clump) and discard the old woody sections. Enrich the soil with peat moss
or compost and replant the clumps so that the eyes are about 1 1/2 inches below
the soil surface.
PHLOX: Phlox can be divided in spring or fall, but
autumn is better. They may need to be divided every 2-3 years. Keep 3-5 stemmed
sections and discard the woody centers. Remember to plant them in a sunny
location with enough space around them to provide good air circulation. This
will help prevent the occurence of powdery mildew disease on the leaves.
HOSTA:
Divisions can be done in the spring or fall. If dividing in spring, do it just
after the new growth pokes through the soil. Ideally, each clump should consist
of at least three healthy shoots.
LILY OF THE VALLEY: These plants are
easily divided in spring or fall. Keep the strongest pips (divisions) and
discard the oldest ones.
CHRYSANTHEMUM: Divide hardy mums in spring
before the shoots begin to lengthen. Remember to pinch the new shoots back once
or twice before July to force the new growth into a bushy form.