Saturday, June 22, 2013

Frozen sundews (with compliments to Carl Mazur)


My yard this morning after a -4.8C frost. The temperature was just rising above freezing as I took the photo; note the termination of the frost along the shadow line on the lawn. The pots were frozen solid and there was an ice film on the water trays.

Recently, fellow CP blogger Carl Mazur from Canada blogged about his success with Drosera binata forms in the USDA climate zone 6b. As Carl was interested to try additional species, I wrote him some suggestions based on my experience in growing Drosera species in the frosty political wastes of city of Canberra, which is the coldest major city in Australia. For the record, Canberra has a USDA zone equivalent of Zone 8. This morning proved to be a fresh one at –4.8C, so I took a few photos of my Drosera surviving under the cold conditions. Hope you enjoy Carl!

You can read about Carl’s wonderful bog gardens and what he grows in them here. Note he insulates his plants with a heavy layer of pine needles to avoid the bog getting too cold. In contrast, I do not insulate the plants with anything, so they have to put up with direct exposure.


One of the plants I suggested Carl try is Drosera pygmaea. This may seem a little like an odd choice for cold areas, but D. pygmaea naturally occurs in very cold parts of both Australia and New Zealand. I’ve seen them growing in abundance in parts of Cradle Mountain National Park, where they occurred at altitudes where snowfall is heavy and persistent (I’d post photos of them, but I sadly lost them to a hard disc crash). In the above photo, you can see a small clump of D. pygmaea in a pot that is quite literally frozen solid. These plants originated from stray gemmae last year. In early winter (after the gemmae made their way into the pot), I moved the pot outside, where they gemmae would have experienced temperatures down to –8C (my readings) and repeat pot freezes and thaws. Yet they grew and produced the above plants. Given where some clones grow in Tasmania, I would think they will take solid freezes. The above clone is a NSW south coast clone, however it is not the only clone to do well here…

Kangaroo Island clone Kangaroo Island clone_b

The above pot contains my parent population of D. pygmaea “Kangaroo Island”, which can be obtained from Triffid Park. It has overwintered here twice and proliferated through many Sarracenia pots, despite the freezing conditions.

Kangaroo Island clone_weedy

Here are more plants of this D. pygmaea clone, this time in a polystyrene tray housing Sarracenia seedlings sown in 2011. I established this tray as a refuge for Drosera as much as for growing out Sarracenia. You can see the amount of frost affecting these plants.


I also grow a range of other sundews outside in the frost with success. The above photo shows plants given to me as Drosera coccicaulis, although I suspect they may actually be Drosera aliceae. The Drosera closest to the camera is D. tokaiensis, the weediest rosetted sundew I grow. Its seedlings in the adjacent pot are arrowed.

frozen capensis

The sundew in the above pot is a Drosera capensis. Although it looks toast, it is quite alive and will re-grow from its roots come spring. Although this is usually the weed for CP collections, I nearly eradicated it in one season between repotting the entire collection and weeding out the dozen or so plants that survived. At the time I was trying to encourage a population of the sundew bugs Setocoris, which are trapped by D. capensis. But the Setocoris did not last the winter and I let the D. capensis come back – it took them two years to break 10 plants! In contrast, D. tokaiensis (which was also down to less than 10 plants) came back a lot faster.

binata multifida extrema

And here is a very subtropical plant – Drosera binata var. multifida form extrema. It died right back and looked like this last year, but came up for the summer. As do the other binata – they always look like they’ve died at this time of year, but always come right on back when it warms up.

frozen capensis 2

An idea I had last year to boost sundew numbers was to create a refuge for Drosera where they would not be disturbed and could re-seed adjacent pots quickly. I did this by using a polystyrene vegetable box filled with CP mix and seeded up with Sarracenia and Drosera. The result – lots more sundews self-sowing through the collection, and insurance for repotting time.

So – its always worth trying different sundews under cold conditions. You never know what will do well…