Transplanting Pink lady-slipper (Cypripedium acaule) - William Cullina

Transplanting Pink lady-slippers (Cypripedium acaule)
Images and text by William Cullina
No plant is more beloved and recognizable than the pink lady-slipper. Unlike most other
species of Cypripedium, it thrives in dry, acidic soils under a thin canopy of deciduous or
evergreen trees. It is found from Newfoundland to Saskatchewan south around the Great
Lakes to the southern Appalachians. In New England, it is by far the most common of
our five Cypripedium
species for the simple
reason that its
preferred habitat is so
abundant here. Still,
as development
converts forest to
subdivision, countless
thousands of pinklady-slippers
have
been bulldozed. It is a
species that is very
difficult to grow under
garden conditions, but
it is possible to
successfully transplant
it to an undisturbed
patch of forest that
offers similar growing
conditions. In a study
we conducted at the
New England Wild
Flower Society, of 75
plants rescued from a
condominium
development, 85
percent were still alive
and thriving after the
sixth season (when we
concluded the study).
Though pink ladyslippers
should never
be moved unless they
are in imminent
danger of destruction,
the purpose of this article is to show you how you can successfully rescue and reestablish
plants from property about to be developed.

It is well known that all orchids have evolved a very sophisticated strategy for seed
germination. Orchid seeds are tiny and lack well developed embryos. To germinate, the
seed must come in contact with a
specific soil fungus which
surrounds the seed as if to digest it.
The fungal roots (hyphae)
penetrate the seed and then the
orchid turns the tide, digesting the
fungus instead. It seems that the
fungus gets nothing from this
arrangement except to be eaten, so
rather than the symbiotic
relationship found with most
mychorrizal interactions, in this
case the union is more properly
called micoparisitism. After 3-4
years in the soil growing larger at
the expense of the fungus, the seeding emerges and begins to photosynthesize for its
food. At this point, it is unclear how important the
fungus becomes to the more mature lady-slipper.
Mature plants can remain underground for several
years after a bad drought, predation, or other
trauma, so it does appear that some continued
relationship is important to the health of the plant.
One plant that I moved in 1990 grew for a few
years then disappeared, only to appear and bloom
again in 2005 then disappear in 2006 and reappear
in 2007 as a two-leaved but non-flowering plant!
Just how widespread the proper group of fungi is
through the range of the orchid is unclear, but
absence of plants in apparently suitable habitat
does not necessarily mean there is no fungus
present. The most important consideration when
choosing a spot for relocation is the pH of the soil,
the available light, and potential competition from
other plants. The pH of the soil is important
because unless the soil is extremely acidic, C. acaule is prone to attack by root diseases
that are naturally suppressed at low pH. Soils with a pH below 5.0 are optimal. You can
test the soil with inexpensive pH test kits or look for indicator plants that like a similar
habitat (obviously, if pink lady-slippers grow there already, it is ideal). In our area of
southern New England as well as most parts of Central and Northern New England, the
soils are considered to be very acidic. Pines, oaks, hickories, spruce, fir, and paper birch
are common canopy species in pink lady-slipper habitat. Some indicator plants to for at
ground level include:

Dendrolycopodium dendroideum Chimaphila maculata Gautheria procumbens
(and other clubmosses) (spotted wintergreen) (wintergreen, checkerberry)
Vaccinium angustifolium Gaylussacia baccata Kalmia angustifolia
(lowbush blueberry and (black huckleberry) (sheep laurel)
other blueberries)
Pink lady-slippers do poorly in deep shade, and this is the most common reason they
disappear over time from a given woods. They are most abundant in either very old
forests with a mixed and broken canopy or in young forest regenerating after logging or
fire. Road cuts and other edge habitats are also good places to find them. I look for
places where the tree canopy has some gaps from windfalls or timber harvest to site

plants rather than in total shade under a continuous canopy.
This is especially important under evergreens. Look for places where the sun breaks
through for an hour or so each day.
Chose areas where the ground is reasonably free of competition. Here huckleberries,
wintergreen, mountain laurel (Kalmia latifolia) and a small white pine indicate good
habitat. I will site the plant just in front of the dead branch in the center.

Though in an emergency, you can successfully move pink lady-slippers at any time
during the growing season, I have had the best results when I moved them in late summer
just as the leaves begin to yellow. This plant flowered earlier in the season, but deer
nipped of the bloom stalk. C. acaule’s roots are very shallow and spread out from the
crown 8-24 inches in all directions, so care must be taken to damage them as little as
possible.
I use a pitchfork to lift the roots gently, coming in
at a shallow angle about 12 inches from the crown
and rocking the fork until the crown lifts up. At
this point I use my hands to help tease the roots free from tree roots and debris. Here the
plant has been lifted with little breakage of the roots and with some humus still
surrounding them.

You can also
remove plants
bare-root as
long as you have
damp burlap to
cover them with
until them are
replanted. This
smaller
individual
has
one welldeveloped
bud
visible in the
center of the
image and a
moderately
sized root
system.
Blackened roots
are stained by humic acids in the soil but still healthy. The white roots are younger.
Lady-slipper
roots will
continue to live
and grow longer
over the course
of about 5 years.
However, if the
growing tip is
damaged on a
particular root, it
cannot grow
another. In this
image, the
healthy white
root began
growing this
spring (after
flowering) as
did the slightly
more stained
one at the left. Notice that this second root has lost its tip and can grow no
longer.
The
roots are all important to lady-slippers as they not only take up water and nutrients
(and perhaps carbohydrates from the fungus) but they also act as the primary foodstorage
organ for the plant during dormancy. If roots are cut or damaged during

transplant, they will stop growing and be vulnerable to infection. The loss of more than a
few can spell disaster for the plant, as it has lost a good share of its food reserves and will
likely wither away over the next year or two. This is a common occurrence in gardens,
where a rescued or wild-collected plant will come up the first year, come back smaller the
next, and fail to return the third. C. acaule’s roots inhabit what is called the F horizon in
the soil. This
is the zone or
layer just
underneath the
unrotted leaves
and other
debris in this
image. A few
roots may pass
through the
narrow H
horizon and
into the black
and gray A
horizon. The
H horizon is
not topsoil, but
rather a porous
blend of
partially
decomposed
organic
materials.
When
replanting the
orchid, it is
essential that
you relocate
the roots in
this layer as
they will
often
rot if buried in
the heavier
horizons
beneath.

I use a digging spade to scrape away the H horizon,
exposing but no removing the lighter A horizon beneath.

Set the plant into this shallow hole and use your fingers to pack the duffy humus
(H horizon) you just scraped off
around the root mass (if the plant is
bare-root, be extra careful to work the
material in, around and between the
roots so as they are spread out).

In this image, a bare-root plant has been set at the proper depth and is ready to be
repacked with duff.
Set the plant so that the tip of the white, pointed bud evident in this image lies just below
the surface when you are finished.

The finished plant with
unrotted leaves spread
back over the roots once
they have been backfilled
with duff. By choosing a
suitable spot, disturbing
the soil horizons as little
as possible and locating
the roots at the proper
depth, I have maximized
this plant’s chances for
success. Other than a
good watering or two to
settle the soil, no
additional water or
supplements are needed.
The same plant the following spring with healthy leaves but no flowers. They are stiff
and just pale enough to let me know they are receiving enough light.

Again, the same plant in its second spring, now with two growths and a beautiful bloom –
both signs that it is settled in and thriving! Notice how the wintergreen in the first picture
has spread beyond the dead branch and around the plant as it heads toward the light.
Good Luck!
©
2007 William Cullina