What are root cuttings, & what Sundews can you effectively propagate with this technique?
Drosera root cuttings can yield mature plants within as little as one growing season. Root cuttings are the most effective way to propagate mature sundews quickly, followed by leaf cuttings, then traditionally sown seed. Both root cuttings and leaf cuttings are considered asexual reproduction versus the more common sexual reproduction that involves flower pollination and seed production.
All plants grown via cuttings will be clones, and genetically identical to the parent plant – so you’ll know precisely what to expect from them. The technique is easy, won’t harm your parent plant, and works with just about any sundew that has long, thick roots. Cuttings are super effective with most rosetted subtropical sundews, Drosera regia, cape sundews, and forked sundews (like the Drosera binata featured in these photos).
When & how to take Drosera root cuttings
It’s best to take root cuttings towards the end of a dormancy period, or early in the growing season – especially if you’re already going to be transplanting your sundews. Start by liberating your plant from its soil. Identify healthy roots that will look black with white tips. Separate out a few of these roots, leaving plenty behind for the parent plant, and use a knife or sharp pruning shears to cut 2 inch sections of root.
Place the root cuttings horizontally on the plant’s preferred soil mix, and cover with 1/4 – 1/2 inch of soil. It’s best to plant them in a propagation tray with a humidity dome, or use another means of keeping conditions humid and warm.
Even though the roots don’t have leaves to photosynthesize yet, it’s important to expose them to bright, indirect light, so place them under grow lights, in a sunny window, or outdoors. Make sure that the propagation tray stays out of direct sun, or you risk overheating and cooking your root cuttings.
Be patient, keep the soil moist, and within a few weeks, you’ll start to notice wee plantlets sprouting from the soil. After a few leaves have emerged, remove the humidity dome from the seed trays, and place the plants in direct light. Give the root systems a few months to establish themselves, and you can replant your Drosera into a more permanent home.
The science behind root cuttings
Plants naturally produce a hormone called auxin that promotes cell elongation, regulates embryo development, apical dominance (condition where the main stem of a plant grows stronger than offshoot stems), vascular tissue differentiation, induction of cell division and, most interesting to the topic of root cuttings in Drosera, induction of rooting. You’ll probably be most familiar with auxin as a hormone produced in a plant’s stem tip that causes it to bend towards bright lights. This happens as the hormone shifts to the darker side of a plant and causes those cells to grow longer than corresponding cells on the brighter side. The hormone indoleacetic acid (IAA) is the naturally occurring version of auxin found in plants.
So, you’re familiar with a Mr. Charles Darwin, right? He was one of the first scientists to explore hormone production in plants, and he identified and described the use of auxins in his 1880 book “The Power of Movement in Plants” after experimenting with canary grass. What a boss. You can buy a copy of his book, or download it for free, here.
When you take a Sundew root cutting, auxin shifts to two primary places in the dismembered root – the root tips, and portions at the top of the root. The top of the root forms nodes and eventually growth points from which carnivorous leaves unfurl. Root tips are encouraged to continue branching, sending out supportive roots to anchor the plant and absorb water and limited nutrients (remember, they’ve evolved carnivorous tendencies because they grow in nutrient-poor soils).
Hurray for plant biology!