Sundew leaf cuttings in water or on peat

Why use leaf cuttings

A sundew leaf cutting grows into an exact copy of the plant it came from. The ICPS leaf cuttings page gives three reasons to prefer that over seed: seedlings vary a lot, so you have to raise many to find a few that suit your conditions; cuttings are the only way to copy a sterile hybrid or a plant that will not set seed; and cuttings usually reach maturity sooner than seedlings ^[1]. Drosera × hybrida, for example, is a sterile hybrid that can only be multiplied this way ^[1], and the ICPS notes the same for the sterile cold temperate hybrids, which are propagated by division or leaf cuttings ^[3].

Leaf cuttings are not the fastest vegetative method for every sundew. For subtropical species, the ICPS says root and stem cuttings give mature plants relatively quickly, while leaf cuttings are slower but still faster than seed. It suggests cuttings as a way to renew a long-lived plant that has started to decline and does not recover with feeding ^[4]. To raise new genetic combinations instead, see sowing seeds.

Which sundews respond

Choosing and cutting the leaf

Take cuttings while the plant is growing vigorously, and use leaves in good condition: fully open, with plenty of dew. The ICPS suggests the best three or four leaves on each plant ^[1]. A plant that has lost its dew is not a good donor; sundew not making dew covers the usual causes.

1. Hold the leaf in your fingers and cut it off somewhere along the petiole, the stalk below the dewy blade, with a razor blade, scalpel or dissecting scissors. Gloves keep the sticky, enzyme-laden mucilage off your fingers ^[1].
2. Cut long leaves, such as those of D. filiformis, into shorter segments ^[1].
3. Cut wide leaves lengthwise through the dewy part to get more plantlets. This helps most with leaves that otherwise make only one plant from the center ^[1].

Most species sprout new plants from the middle or the edge of the tentacle-bearing part of the leaf, so the blade is what matters ^[1].

Method A: floating in pure water

The ICPS calls water the cleanest medium and its author’s preferred method ^[1].

1. Fill a small jar with about 1 cm of distilled or reverse-osmosis water, or use a test tube ^[1].
2. Float the leaves tentacle side up. In a tube, trim them to whatever length fits ^[1].
3. Close the jar with a plastic lid or plastic wrap, or cap the tube ^[1].
4. Label it with the species and the date ^[1].
5. Change the water if it turns cloudy ^[1].
6. When the plantlets have a few leaves, plant them in their normal mix, such as peat and sand. The ICPS author buries them slightly with pure sand ^[1].

The advantage is survival time: leaves last longer in near-sterile water, which matters for species that are slow to start ^[1]. The ICPS photos show D. × hybrida in small jars and D. binata in a tube ready to be planted out ^[1]. Use the same pure water as for the adult plants; see water.

Method B: on peat, sphagnum or sand

Almost any medium the adult plant grows in will do: live or dried long-fibered sphagnum, peat, peat and sand, or sand ^[1].

1. Keep the medium very wet ^[1].
2. Lay the leaves on it and partly cover them, so they stay in contact ^[1].
3. Put the pot in a plastic bag or sealed terrarium to hold the humidity at 100% ^[1].
4. Add a tag with the species and the date ^[1].

The trade-offs, according to the ICPS: peat can feed the leaf and later the plantlets a little, live sphagnum is thought to protect against mold and keeps the medium acidic, and plantlets can stay put because they are already in a growing medium. Against that, these media carry molds, cyanobacteria and moss spores, and the leaves can shift out of contact, so they need more watching ^[1]. D. regia leaves in particular tend to rot on soil ^[8]. The PlantZAfrica profile of the Cape sundew from Kirstenbosch describes the same soil method for D. capensis: partly cover the cuttings with growing medium, keep the pot covered with plastic in good light but out of direct sun, and pierce the plastic to harden the young plants off once new leaves appear ^[5]. More on enclosed containers is in terrariums and humidity.

Light, warmth and waiting

Cuttings need plenty of light without overheating. The ICPS considers fluorescent lights safe at no less than 30 cm (12 in), and in a greenhouse suggests a shaded spot or the space under the bench. Tropical species such as the D. petiolaris group want it warmer ^[1].

Then comes the wait. Little happens in the first month or so. D. filiformis and D. binata may burst into growth in the second month, while D. slackii can sit for 5 months before doing anything ^[1]. No success rate is published. Not every leaf makes it: remove leaves that turn completely brown or grow fungus, but do not give up on any leaf with green or red left in it ^[1]. A D. prolifera photo on the ICPS page shows old leaves still red and dewy 4 months after cutting ^[1].

Where the plants appear varies by species. D. spatulata usually makes a single plant from the center of the leaf; D. prolifera sprouts near the edges, even from leaves that look burnt; D. binata can produce plantlets one or two millimeters apart. Most species are slower, producing a few plantlets that grow slowly ^[1].

When to use root cuttings or pullings instead

For D. regia and other sundews with thick, rope-like roots, the ICPS recommends root cuttings ^[1]. The D. regia guide takes older roots whenever a plant is transplanted, buries 2 cm pieces about 1 cm deep in loosely packed long-fibered sphagnum, and moves the new plants to peat and sand or peat and perlite once their leaves are 2 to 3 cm long. Some growers float the root pieces over sphagnum in water instead ^[8].

Plants of the D. petiolaris group sprout from the leaf base where it joins the stem, so the leaf has to be pulled off with its stipule attached. It risks damaging the parent, and even a clean pulling is no guarantee of new plants ^{[1, 2]}. D. binata also grows readily from root cuttings, and because most forms in circulation are traded as cuttings, many plants of one form are clones of the same plant ^[6]. The Drosera overview explains these groups in more detail.