Grow Carnivorous Plants in a DIY Mini-Bog
If you were asked to imagine a landscape inhabited by carnivorous plants, you might envision some primeval jungle of contorted vines and fearsome beasts. In reality, unless you live on a research station in Antarctica, chances are that some ferocious flora is growing very near you.
An expedition to see wild carnivorous plants in New York City, for example, could consist of a free ferry ride to Staten Island, where the spoonleaf sundew (Drosera intermedia), with its glistening “sticky-trap” leaves, can be seen at Clay Pit Ponds State Park Preserve. Several aquatic carnivores of the genus Utricularia also grow in the kettle ponds that dot the borough. Far from being delicate, tropical novelties, many carnivorous plants grow well in the New York City region, and they can be easily cultivated outdoors in most parts of the country in USDA Zones 5 through 10.
In the wild, most carnivorous plants grow in sunny, acidic, nutrient-poor wetlands called bogs. Home gardeners can replicate this environment in a mini-bog planter and grow a diverse array of species like sundews, pitcher plants, and butterworts. You can also include orchids and other noncarnivorous wetland plants to build a fascinating miniature habitat. There's no need to hand feed your carnivores—insects will readily come on their own. Expect to see houseflies and wasps fall prey to your flytraps and pitcher plants.
Below are instructions for constructing a mini-bog using a basic pond liner from a home-improvement store, but you can adapt the idea to other containers too—almost any plastic or metal container without drainage holes can be used to replicate boggy conditions, from a window box or flowerpot to a more idiosyncratic vessel like a salad bowl, tool box, or even an old rain boot. Plan to keep your mini-bog container outdoors in a sunny location for most of the year.
- Carnivorous plants Select species that thrive in your climate and site conditions (see below for more details).
- Rigid high-density polyethylene pond liner, with no drainage holes One choice is a MacCourt 9-gallon black liner, 26 inches wide and 7 inches tall, which can be purchased at Lowes or another home-improvement store.
- Round plastic nursery plant pot (approximately 6 inches tall and 10 inches wide) This pot must have drainage holes.
- 1.5-quart bag of horticultural lava rock
- 1-cubic-foot bag of sphagnum peat moss The packaging must literally say “sphagnum” peat moss. Sedge peat and sweet peat are not acceptable. It should not have any added nutrients.
- 40- to 50-pound bag of horticultural sand or washed play sand Do not use paving sand or sand from a beach.
- 100-cubic-inch bag of fibered sphagnum This is simply dried sphagnum moss.
- Optional top-dressing materials Try pine straw, pine bark, live sphagnum, and/or quartz gravel.
Step 1: Provide Drainage
Fill the bottom two inches of the pond liner with crushed lava rock for water space.
Step 2: Make the Reservoir
Place your plastic nursery pot in the center of the pond liner. You will keep this pot empty and fill the container around the pot with soil. Once the mini-bog is complete, you will fill this pot with water, which will slowly drain out into the pond liner to bottom-water your plants.
This allows you to avoid top watering, which can disrupt small plants and compact the soil. The pot also functions as a bog-garden reservoir, reducing the need to water as frequently. Simply refill the pot when the water level drops to its bottom.
Step 3: Prepare the Soil Mix
Create your growing medium by combining 50 percent sphagnum peat moss, 30 percent horticultural sand, and 20 percent long fiber sphagnum moss and saturating it with water until it has a mudlike consistency. Fill the planter (outside the plastic pot) with the soil mix.
If your mini-bog is to be viewed from all vantages, consider building the soil level higher toward the middle of the pond liner for visual appeal. Or vary the depth of the soil and then plant the lower areas with more flood-tolerant species like spoonleaf sundew and parrot pitcher plant (Sarracenia psittacina). Higher areas can be planted with less flood-tolerant species like Venus flytrap (Dionaea muscipula).
Step 4: Select and Install Plants
Your mini-bog can include a mix of carnivorous plants and other species that thrive in bogs. When choosing carnivorous plants, cold hardiness is your biggest concern. If you live in Zones 7–10, you can grow Venus flytraps, most American pitcher plants (Sarracenia species), and most temperate and warm-temperate sundews (Drosera species) and butterworts (Pinguicula species).
If you live in Zone 6, focus on plants from the Carolinas and farther north, like trumpet pitcher plant (Sarracenia flava), sweet pitcher plant (S. rubra), and purple pitcher plant (S. purpurea).
If you live in Zone 5 or colder, you are limited to very cold-tolerant plants like the northern subspecies of purple pitcher plant (Sarracenia purpurea subsp. purpurea), round-leaf sundew (Drosera rotundifolia), English sundew (Drosera anglica), and common butterwort (Pinguicula vulgaris).
Regardless of your climate, there will be no shortage of options for beautiful bog plants to accentuate your carnivores. A succession of orchids is one great option and will add seasonal interest. Try grass pink (Calopogon tuberosus), which blooms in spring to early summer, followed by the late-summer-blooming nodding ladies' tresses cultivar 'Chadds Ford' (Spiranthes cernua var. odorata ‘Chadds Ford’).
Only purchase carnivorous plants and orchids from reputable nurseries and dealers. Poaching of wild carnivorous plants and orchids threatens the continued existence of these incredible botanical wonders. (See below.)
Once you have selected and acquired your plants, think about placement. If your mini-bog will be viewed from all sides, you may want to plant your tallest species toward the center and then terrace down to shorter plants. If it's to be viewed primarily from one side, plant your tallest species at the back and install shorter plants in the front.
Step 5: Top Dressing
Once you have installed your plants, you can top dress your mini-bog with pine needles, pine bark, quartz stone, or live sphagnum to add a sense of realism and protect your plants from the impact of heavy rain. Top dressing may also help protect your plants from marauding squirrels and birds.
Water quality is always an important concern when growing carnivorous plants. Unless you live in a city like New York, where the tap water has less than 100 parts per million dissolved solids and a pH lower than 8, you should only irrigate your mini-bog with distilled water, reverse osmosis water, or rainwater.
When watering the mini-bog, fill the reservoir pot to the top and then let the water level drop to near the bottom over a period of days, so that oxygen can periodically permeate the soil. If you live in a very rainy region and you find that the mini-bog is constantly flooded, drill some holes in the side of the container about an inch below the surface of the soil to allow drainage.
Your mini-bog must be positioned where it will receive at least five to six hours of direct, unobstructed sunlight.
For most carnivorous plants native to the United States, a winter dormancy period is required for long-term survival. If you are growing plants not winter hardy in your region, you may need to shelter your mini-bog during the winter while still allowing the plants to experience natural dormancy. At the outset of freezing temperatures, move the mini-bog to a sunny glassed-in porch or a windowed basement where it will be cool but protected. Alternatively, leave the mini-bog outside, but bury the pond liner so that its surface is at the same level as the ground, and then mulch the top with two to three inches of pine needles or straw.
Once established, your mini-bog will require minimal maintenance. Just weed and water the container, and you can expect your mini-bog to last for years. Flies and wasps, beware!
NurseriesRare Find Nursery
Jackson, New Jersey
Meadowview Biological Research Station
Carnivorous Plant Nursery
For additional information on growing carnivorous plants, Brooklyn Botanic Garden will offer the workshop Cultivating Carnivorous Plants on July 30, 2016, instructed by Will Lenihan, who wrote this article.