From Glistening Dew to Deadly Trap: The Remarkable Sundew Plant

Carnivorous Sundews sparkle in the sun and wait for their prey to get caught in the glistening drops of sticky glue covering the leaves on tiny stalks. These fascinating plants are the most diverse of the carnivorous flora, growing in acidic, low-nitrogen fens and bogs on every continent except Antarctica.

There are nearly 200 types of Sundews species, generally classed into 14 subtypes, depending on where they’re native and their growth habit.

Eight species of Sundews and their naturally occurring hybrids grow in pine barrens and boggy areas down the eastern seaboard of the U.S. from Massachusetts to Florida and Mississippi, as well as in Texas, Oregon, and California. These U. S. Sundews are cold-hardy, temperate types that are not commonly available to buy and can be challenging to grow.

However, some of the tropical types, such as Drosera capensis, are frequently available and are good choices for beginning gardeners and school science projects. The highest tropical Sundew concentration is found in South America, South Africa, Australia, and New Zealand.

What Do They Look Like?

drosera spatulta capensis

Sundews come in all shapes and sizes, depending on the species. They are generally small, with an average size of 2 to 8 inches high, but some species can grow 2 to 3 feet. Their leaves can be long and slender, short with spoon-shaped tips, or wide with rounded tips.

Some species grow in an organized basal rosette, while others grow in a seemingly random group of arching leaves.

The upper surface of the leaves is covered with little red stalks called “tentacles” that each produces a drop of clear, sweet-smelling mucilage to snare its prey. The drops sparkling in the sun are what give Sundews their name.

From June to September, the plants send up leafless stalks with buds that open into small, white, or pale pink, 5-petalled flowers. They only open for a few hours, are self-pollinated or pollinated by insects, and then begin their development of seeds.

Why Do They Trap Insects?

drosera spatulta capensis

All green plants, including Sundews, use water, sunlight, and carbon dioxide to make their energy food (sugars) through photosynthesis. Most plants get the rest of their nutrition, such as available nitrogen, phosphorus, potassium, calcium, magnesium, and micronutrients from the soil.

But since carnivorous plants live in acidic, nutrient-poor bogs and fens where these minerals are unavailable, they have adapted to get their minerals by trapping and digesting insects and other small critters.

How Do They Trap Insects?

drosera with a wasp

The glistening drops of fragrant, sticky glue on the leaves are what attract bugs to the plant. When one gets caught in the glue, the leaf curls over, trapping the insect. Enzymes envelop the bug and break down its body into nutrients that the plant can use.

All temperate and tropical Sundews use the same method of snagging their prey for nutrition.

Sundews Plant Care & Feeding

Drosera capensis
Drosera capensis

It’s important that you know whether you have a temperate or tropical plant because their care is somewhat different. Here are examples of temperate and tropical Sundews that are currently on the market:

Temperate SundewsWhere Native
Drosera filiformis – Threadleaf SundewNova Scotia, Massachusetts, New York, Pennsylvania, New Jersey, North Carolina, and Florida
Drosera × hybrida – natural hybrid of D. filiformis and D. intermediaNew Jersey pine barrens
Drosera intermedia – Oblong-leaved SundewEurope, northeastern Canada, eastern U.S., northern South America, Cuba, Hispaniola
Drosera tracyi (D. filiformis var. tracyi) – Tracy’s SundewSoutheast U.S. Gulf Coast
  
Tropical SundewsWhere Native
Drosera adelae – Lance-leaved SundewQueensland, Australia
Drosera aliciae – Alice SundewCape Province, South Africa
Drosera capensis – Cape SundewCape Province, South Africa
Drosera spatulata – Spoon-leaved SundewSoutheast Asia, Australia, New Zealand

Light

Both temperate and tropical plants need about 4 hours of direct sun a day and the rest of the time in bright, filtered, or indirect light.

Temperate or cold-hardy Sundews are best grown outdoors in pots because they need a lot of sun and several months of cold-weather dormancy in the fall and winter. During that time of year, keep their containers on a sunny porch or patio, protected from too much wind but in plenty of sun. Low light will cause their leaves to droop and stop producing the dewy drops of glue.

Tropical Sundews, however, do best indoors on warm, sunny windowsills all year round.  Unobstructed west- or south-facing windows will give them the light they need during the spring and summer, but they may need some supplemental light from a grow bulb during the fall and winter.

If you only have an east- or northern exposure for your plants, supplement the available sunlight with a grow bulb or a strong fluorescent light positioned about 12 inches above the plant.

Temperature & Humidity

Temperate Sundews are resilient to both high and low temperatures – they can handle temperatures above 90 degrees F and down to 20 degrees without protection so that you can leave them outdoors all year round without harm.

If temperatures drop below 20 degrees, however, cover your plant and set it in a sheltered spot, like in an unheated shed.

Tropical Sundews can only be outdoors if you’re in a subtropical or tropical area with temperatures that never dip below 55 degrees. They need warmth, steady temperatures, and plenty of sunshine, so keeping them indoors is safer.

All Sundews prefer high humidity, and temperate species should be fine outdoors. Tropical ones, however, may need some supplemental humidity to keep them producing their sticky dew, especially in the winter when the heat is on indoors.

They grow best with 40-50% humidity levels, so a humidifier near the plant will be helpful.

Dormancy

Temperate Sundews stop growing and begin to drop their leaves in the late summer and fall and develop dormant buds (hibernacula). Increasingly lower light and temperatures below 50 degrees F trigger dormancy that lasts for several months.

Growth resumes when the dormant buds sprout into new leaves in the early spring.

During dormancy, keep the soil moist and cut off the dead leaves in the spring as the new ones are developing.

Most tropical Sundews grow all year and do not hibernate.

Water

It’s essential that you use the correct type of water for your plant. “Hard” water with a high volume of dissolved minerals will kill your plant quickly.

Check with your local water authority to see the mineral level in your water. If it’s close to ±50 ppm mineral content, you might be all right to use your tap water. You shouldn’t use it for your plant if it’s 150-200 ppm or above. Healthy alternatives are mineral-free rainwater, reverse-osmosis water, or distilled water.

Bottled spring water is not recommended because of the high mineral count.

If you do use tap water, flush the soil with rainwater or distilled once a month to eliminate any buildup of minerals and keep the plant healthy.

Keep the tray under the pot filled with ½” to 1” of water during the growing season to maintain very moist soil.

Soil

It’s important to grow both temperate and tropical Sundews in acidic, nutrient-poor soil that retains moisture. The soil the plant initially came in will be fine. But if you need to repot your plant or combine it in a container with other carnivorous plants, you’ll need the right kind of fresh soil.

NOTE: Never use garden soil, indoor potting mix, fertilizer, or compost for your Sundew.

Commercial carnivorous plant soil is specially formulated for these plants and will work fine, or you can make your own, which is more cost-effective. The pH of the soil needs to be acidic – between 5.0 and 6.5. (You can test it yourself with a home pH meter.) The recipe is easy – 50% peat moss and 50% perlite.

The first step is to hydrate the peat moss. Put it in a bowl with water and let it sit for half an hour to absorb the water. Pour off the remaining water, then mix it with perlite, and you’re ready to plant your Sundews.

Pot

Sundews do best in ceramic, glass, or plastic pots rather than terracotta to retain the water in the soil better. It’s best to choose a pot with a drainage hole so you can flush water through the soil occasionally to get rid of a buildup of minerals and constantly hydrate the soil from the bottom tray.

Give your plant plenty of space, too, with a pot that might look too big. Sundew roots spread and grow deep into the soil. If you give it enough room, your plant will be able to grow larger.

Feeding

Outdoors, temperate Sundews will catch as many insects as they need. It is only necessary to feed them yourself if their growth is sluggish and they need some extra nutrition.

Tropical Sundews growing indoors may catch a few small insects in the house, but it will not be enough. You will need to feed them regularly to maintain their nutrition.

Feeding Sundews is easy, but there are a few things to understand.

  1. Keep the size of the bugs small enough in proportion to the leaf so that they can’t escape and can be completely digested. Too large a bug that is partially digested may begin to mold on the leaf, causing damage.
  2. Sundews can digest both live and dead insects and spiders. Freeze-dried bloodworms, betta fish flakes, and pulverized betta fish pellets are also excellent, nutritious choices.
  3. You can feed mature plants several bugs, one to a leaf, every 2-3 months.
  4. Feed young plants several bugs, one to a leaf, once a month.
  5. Place the bugs, bloodworms, or fish food directly on the dew drops with tweezers.
  6. It will take several hours to several days for the plant to fully digest a bug, depending on the size of the bug and the species of the Sundew.
  7. It takes a lot of energy for the plant to digest a bug, and overfeeding can harm it.
Appropriate Food for Your SundewWhat Not to Feed Your Sundew
AntsBeef/pork/ham/chicken/turkey/fish
GnatsStink bugs
FliesLarge insects like grasshoppers
CricketsSlugs/snails
SpidersPlant fertilizer
MosquitoesBees/wasps/hornets
Fruit fliesFruit
SpringtailsMilk

3 Common Problems

Closeup view of Cape sundew "Drosera capensis White flower" with dead fly.

1. Not producing enough dew

Refusing to produce enough glue is the most common problem when growing Sundews and is caused by various stressors to the plant.

Insufficient light doesn’t give the plant enough energy to produce the sticky mucilage to trap insects. Make sure it is getting about 4 hours of direct sunshine a day.

Too much sun, however, can burn the glue-producing glands, especially in the summer. If your temperate Sundew living outdoors is slowing down in its dew production during the summer, it may be due to too much sun. Move it to a location with bright indirect light for part of the day.

Low humidity and drafts can keep the plant from producing dew. Use a humidifier for your indoor plant and keep it away from hot air or air conditioner vents.

When the roots have been disturbed by repotting, the plant may stop producing its glue for a couple of weeks. A healthy plant will resume making glue when it becomes established in its new soil.

2. Leaves are dying or turning brown

Some Sundew species don’t like hot weather, such as Drosera capensis, the most commonly sold Sundew. This South African plant grows best in steady, average temperatures, like in a typical household. Keep it indoors on a sunny windowsill, away from hot or cold drafts.

3. Pale color

When your plant can’t produce its usual vivid colors, it isn’t getting enough sunlight. The red tentacles will turn green in low light, and the whole plant will look pale. Increase the amount of sunlight, either in strength or in the number of hours, or use artificial grow lights.

Author & Editor | + posts

Nancy has been a plant person from an early age. That interest blossomed into a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Nancy worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.