Cultivating Carnivorous Plants (2015)
GROWING CARNIVORES OUTSIDE
The world of carnivorous plants
is so diverse that it is possible for
many growers to grow at least some
of their collections outside. For the
majority of growers, that means either
keeping large pots outside or creating
a bog garden. For others, it means the
creation of a carnivorous pond. For a
very select few, it means either
planting some plants directly outside,
making slight modifications to the soil
to allow for the planting of carnivores.
Many growers live in climates
that allow them to grow plants
outside, although that may require the
installation of a semi-permanent bog
garden or carnivorous pond. In this
section, I will cover the basics of
Atlanta Botanical Garden’s Bog Gardens.
creating those fixtures.
In the case of both bog gardens and carnivorous ponds, it is wise to grow the plants in the intended
location for an extended period (about a year) before creating a semi-permanent structure. Doing so will
mitigate any surprises in growing conditions that may reveal that the chosen location is not ideal. Oftentimes,
one area of the yard may appear ideal during one season, but turn out to be less than ideal during another
Creating the Bog Garden
Creating a bog garden is an easy, if long, endeavor. The first step is choosing a location. Most carnivores
prefer sunny locations that are not exposed to harsh winds. It is also important to assess the slope of the land.
Although low-lying areas may, at first, appear ideal, these areas will also accumulate runoff during rainstorms.
CULTIVATING CARNIVOROUS PLANTS
This runoff can cause flooding of the bog
garden, burying of more sensitive plants, and
differences in media height. Additionally, if
neighbors use fertilizer or pesticides on their
lawns, the substances can accumulate in low-
lying areas and thus change the soil chemistry
of the bog garden.
After a suitable location is chosen, a
decision needs to be made regarding the liner
or base of the bog garden. Few growers will
live in an area where it is possible to avoid
purchasing and installing some kind of plastic
or vinyl liner. When choosing a liner, one will
want to consider whether the bog will be
above-ground or in-ground. Above-ground
bogs will have soil that becomes warmer in
summer, and stays colder in winter. They do,
however, work better with some landscape
designs and are easier to maintain.
If installing either an above-ground or
in-ground bog, a typical, flexible, vinyl pond
liner may be used. If, however, an in-ground
bog is desired, hard plastic liners or reused
large plastic tubs or pots may be used. No
matter which type of liner is chosen, the
installer will want to dig out the soil a bit and
backfill with sand all around the liner.
Depending on the soil composition, the sand
should be up to 6 inches deep. The sand
serves as a cushion against in-soil items, such
as sharp rocks and tree roots, and prevent the
seasonal expansion and contraction of the
liner and bog from puncturing the liner.
If the bog is installed in an area that
receives a lot of rain, one or two drainage
holes should be made in the bog. These
A pot of Sarracenia which could either be displayed on a
drainage holes should be on the side of the
porch, as shown, or buried to create a mini-bog garden.
bog, a few inches below the surface of the
bog. Place them deep enough that they will
allow the surface of the soil to dry, but not so deep as to cause small plant roots to be unable to reach the
moisture. A hole at the bottom of the bog may also be a good idea. Note, however, that holes can encourage
worms and other soil-dwellers to enter the bog. If too many enter the bog environment, they can wreak
havoc with plants.
Most growers fill a bog with a standard carnivorous plant media mixture. This mixture consists of one
part sphagnum peat and one part sand. As always, perlite may be substituted for sand, but be careful with use
of this soil additive. It will float in water, and, in bogs which receive lots of water, the perlite will float to the
surface while the sphagnum peat settles, causing the soil to separate over time. Other soil items, such as
coconut fiber or long-fiber sphagnum, can be substituted for the sphagnum peat, but these items are often
more expensive than sphagnum peat.
Some growers will add live sphagnum as a top-dressing and soil refresher. Be careful if using live
sphagnum. Often, it is harvested from wild bogs. Many times, this harvesting is done in an unsustainable
manner and harms carnivores native to that area. Such harvesting should be discouraged. Additionally, the
introduction of live sphagnum can result in the introduction of a host of pests and pathogens into a bog,
depending on where the sphagnum was harvested and what is living in it.
Creating the Carnivorous Pond
Not all carnivores are terrestrial.
Many are aquatic. Creating an outdoor
pond for carnivorous plants is a great
way to grow many of those aquatic
species, especially Aldrovanda vesiculosa.
There are two major routes for
creating a carnivorous pond. First, a
pond may be attached to a bog. This is
a fairly easy route. Either a depression
may be made in a poorly draining bog
and that depression, filled with water,
carnivores, or a separate pond area
may be created. The best way to create
the separate pond area is to build it at
the same time as the bog, and separate
the soil in the bog from the pond with
a screen, which is folded into the bog
in such a way that the weight of the
bog soil holds the screen in place.
An aquatic tank with both Aldrovanda and Utricularia, as well as
The second route for creating a
non-carnivorous plants, including Duck Weed, a good companion
carnivorous pond is to create a
plant for carnivorous plants.
freestanding pond. Essentially, the
same basic steps are taken as when
creating a bog: pick a location, pick a liner, and build the pond. The difference comes with the filling of the
liner. Instead of filling the liner with a media mixture, a thin layer of sphagnum peat should be laid on the
bottom of the pond. Use about an inch (2.5 cm) of sphagnum per six inches of water. Non-carnivorous
plants, such as water lilies or reedy-plants should be planted directly in the sphagnum soil. If the builder wants
to discourage the spread of non-carnivorous plants, those plants should be left in their nursery pots, or
planted in net pots, i.e. pots which have numerous holes all around them.
Which non-carnivorous plants should be added is a tricky question. Many non-carnivorous aquatic
plants need to be evaluated not only for their suitability in an acidic environment, but also for their invasive
nature. Some species which are commonly used, such as Water Hyacinth ( Eichhornia crassipes), are highly
invasive and should not be used. Good candidates for non-carnivorous aquatic plants include reedy plants,
CULTIVATING CARNIVOROUS PLANTS
such as Papyrus, and water lilies. Some carnivores, especially Aldrovanda, prefer reedy plants over other
After the pond water settles and the non-carnivorous plants have been growing for a week-or-so,
carnivores may be introduced. For many aquatic Utricularia, no more need be done than placing the plants in
the pond. Their prey will appear in the water, almost as if by magic. For Aldrovanda and some species of
aquatic Utricularia, it will be necessary to introduce some leaf litter - only an inch (2.5 cm) or so - to the
water, and allow that to settle, before introducing those species.