GROWING CARNIVORES OUTSIDE - Cultivating Carnivorous Plants (2015)

Cultivating Carnivorous Plants (2015)


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.



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,



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.