Sowing carnivorous plant seeds: surface sowing, step by step

Start with the right seed, and the right expectations

The ICPS seed guide is frank about the odds. A few carnivorous plants can reach maturity within a year under ideal conditions, but most take two to six years from seed, and everything has to go right for all of that time. Its advice to beginners is to start with plants rather than seed, and when you do try seed, to begin with the faster, more forgiving species and not to sow a whole packet in one pot at one time ^[2].

Get seed from plants in cultivation: your own, other growers’, or a seed bank such as the ICPS Seed Bank. Never gather it from wild plants. The ICPS condemns field collection as unethical when nursery-grown stock is freely available ^[3]. Its wild seed page explains why seed matters too: many areas require permits to collect seed, carnivorous plants often grow in small populations, and taking seed can reduce a site’s genetic diversity. The Seed Bank will not accept field-collected seed of the species on its Imperiled Carnivorous Plant Species List, which includes the Venus flytrap, Drosera regia and Sarracenia oreophila ^[4]. For the flytrap, the US Fish and Wildlife Service lists state felony laws against poaching and the supply of ethically grown plants among the factors protecting wild populations ^[5]. The buying plants legally guide covers the law in more detail.

Which seeds need what

The ICPS step-by-step method is written for tropical, subtropical, pygmy, woolly and warm temperate sundews, Drosera regia, Venus flytraps, warm temperate butterworts, Genlisea and terrestrial bladderworts, with side notes for other groups ^[1]. The group guides add temperatures and timings.

Nepenthes seed is short-lived and can be killed by freezing in the mail; the ICPS reports that about half the Nepenthes seed its Seed Bank receives is already dead ^[12]. Check tuberous Drosera seed with a hand lens before sanding it: not every species has hard seed, and sanding destroys the seed of some, such as D. auriculata ^[13].

What you need

• Tags and a soft pencil. The ICPS page uses vinyl plant tags written with a #2 pencil or 0.9 mm soft mechanical lead, and dismisses “permanent” markers ^[1].
• A planting spoon, which it calls the most important tool ^[1].
• Sturdy pots, with the drain holes covered by squares of polypropylene landscape fabric so the soil does not wash into the tray ^[1].
• Soil ingredients: horticultural-grade sphagnum peat with no added fertilizer, and coarse #12 sand-blasting sand (14 and 16 mesh also work). Play, builders’ and beach sand pack too tightly unless sieved and washed ^[1]. Coir suits Nepenthes only, and only a brand leached by rain; ordinary coir blocks are too salty ^[1].
• Plastic bags, or a covered aquarium or clear storage box, and LED lights ^[1].
• Pure water with less than 80 ppm dissolved solids, which in most places means reverse-osmosis, distilled or deionized water ^[2]. See water.

Step by step

1. Set up somewhere you can make a mess, with everything at hand ^[1].
2. If you are sowing seed that needs a cold period and will not overwinter the pots outdoors, stratify it in the refrigerator first ^[1].
3. Put a fabric square in the bottom of each pot ^[1].
4. Choose the mix. The default is 1:1 peat and sand by volume. Woolly sundews and relatives of Drosera indica prefer it sandier, warm temperate butterworts peatier, and Nepenthes do well in coir. For seed that is slow to germinate, a top centimeter of finely chopped sphagnum is an option ^[1]. Many growers rinse their ingredients first to cut down salts, nutrients and weeds ^[1].
5. Mix the peat and sand while damp rather than wet, fill the pots loosely to the top, then firm and level the surface lightly with the spoon. Do not pack it hard, because the mix swells once it is saturated ^[1].
6. Write the plant name and the date on a tag and push it in along the side of the pot ^[1].
7. Scatter the seed over the surface without burying it ^{[1, 2]}.
8. Mist the seed and soil lightly with pure water ^[1].
9. Pour a little water into a plastic bag and stand the pot in it; the extra water is needed because the mix is not yet fully soaked. Check later that some water is still left in the bottom ^[1].
10. Put the bagged pots under LED lights and check them weekly. An occasional light spray of the surface can encourage sprouting, and Nepenthes appreciate it weekly ^[1].

Pots that need a natural winter can go outdoors instead, somewhere out of direct sun and protected from animals ^[1]. Terrestrial bladderworts are the wettest case: the ICPS guide sows them on wet to very wet medium and stands the pots in bags holding a few centimeters of water ^[14].

Light, moisture and heat while you wait

The ICPS germination guide suggests 16 hours of light a day, with fluorescent tubes 15 to 25 cm above the pots, a sheet of glass or acrylic to cut the heat, and enough air movement that the plants do not cook ^[2]. Pots of wetland species should stand in a little water with the surface sprayed so it never dries; fog forest and jungle species need very moist soil but not standing water. A bag that stays fogged is wet enough ^[2]. Mexican butterworts are the exception among the warm germinators: their soil should be damp, not sopping ^[11].

Never put bagged pots or humidity domes in direct sun. The ICPS Sarracenia seed page rules it out, and the scarification page warns that covered pots in the sun produce roasted seedlings ^{[15, 13]}. The light guide covers lamps for seedlings.

Moss, cyanobacteria and fungus gnats

The usual enemies are not disease but competition and pests. The flytrap guide explains that the nutrients in peat feed cyanobacteria (blue-green algae), which can smother tiny, slow seedlings; washing the peat helps, and live sphagnum can overgrow the plants if it is used ^[6]. The subtropical sundew guide expects to move seedlings to fresh medium a few times, using fine forceps, a magnifier and bright light, and taking care with the roots ^[7]. Pygmy sundews are harder to rescue, because their roots are long and break easily ^[8].

Fungus gnat larvae eat seedling roots. Keeping the pots sealed in bags and away from other plants keeps the gnats out ^[2], and the subtropical sundew guide advises leaving seedlings bagged until they are big enough to survive the larvae, as long as moss is not a problem ^[7]. See fungus gnats.

After germination

The flytrap and sundew guides take the pots out of their bags once the seedlings have a few true leaves and move them to a bright terrarium or greenhouse ^{[6, 7]}. Keep records. The ICPS guide calls a germination wait of many months an eternity without dates to check against ^[2].

Growth is slow until the seedlings are big enough to feed. The ICPS seed guide says it can take a year to reach that point for many species ^[2]. Subtropical sundews can easily take two years to mature; the hard part is getting seedlings big enough to feed with rehydrated bloodworms, after which they grow quickly ^[7]. Venus flytrap seedlings tend to grow for about four months and then stop, expecting winter; the ICPS guide keeps them going with warmth, strong light and heavy feeding, and estimates five years to maturity without regular feeding, or two years with as much feeding as the plants can take ^[6]. Nepenthes can stay in their bags under lights for one to two years and take 3 to 5 years to become display plants ^[12].

Expect variety in a pot of seedlings. The ICPS sowing page shows Nepenthes ventricosa seedlings of very different sizes at 10 months and recommends sowing far more seed than you need so you can choose the best plants, keeping some small ones in case the largest are accidental hybrids ^[1].