Growing Darlingtonia–third time’s the charm?

Cobra lillies (Darlingtonia californica) are one of my favourite plants – not that you’d know it at the moment given I mainly post about Sarracenia flava. But if you look back through this blog, you’ll see I used to grow it to a reasonable size (at least by Australian standards) until I lost my plants during hot, still weather soon after we moved house. I’ve tried it a few times since (including in my bog gardens) and lost it each time. When the AUSCPS meetings started up here in Canberra, I brought some to try a few ideas on how to grow it here.

The first two attempts failed because a bird (magpie?) uprooted the plant and dropped it on hot concrete while we out, and the second because the plant was not watered while I was away with work.

The third time seems the charm – I managed to get the plant through the first batch of hot weather (including 11 days straight above 35C and nights above 20C). I did this by keeping the plant in a ventilated site in the shade. That said, it looked very miserable.

My experience with Darlingtonia is that they like an open and airy mix in a broad, shallow tray that is regularly flushed with water, with the plants kept in a shady and breezy (but not windy) position. The plants I got recently were all in a standard height unglazed terracotta pot in 1:1 peat: sand media with Sphagnum top dressing, which I felt was not open enough based on how slowly it drained if wetted (the smell of the media at the bottom of the pot also told me the conditions were anaerobic and thus stagnant).

After the Christmas heat wave, I repotted the last remaining plant into a very coarse mix of 1:1 scoria: Sphagnum, which has worked well for me previously. A note in preparing this mix – it is important that the moss strands are completely separated, as they tend to form clumps or balls that don’t mix evenly with the scoria. I try to mix it by layering spread strands of Sphagnum across the pot and then covering it one stone deep with scoria and repeating.

Here is the result:

The plant is clearly not happy given previous treatment – but it had a good, healthy root and rhizome system, so its capable of trying. The new mix drains very quickly, which is a good thing for keeping the medium aerated, while the Sphagnum holds a lot of moisture. The trick will be to flush it out with water every day to keep the moisture up to allow evaporative cooling across the terracotta. I think shallow Terracotta planter bowls work well because they have a larger surface area than a tall pot (if you consider the surface area of the top of the pot as well), which maximises cooling and aeration potential. Not sitting the pot in a deep tray of water also forces water to evaporate from the sides of the pot. I have this plant next to the door of our sunroom where it gets bright, indirect light and a good breeze blowing across it most of the day to help keep it cool. Despite an air temperature of 28C this afternoon, the pot was almost cold to the touch, so it seems to be working.

Here’s hoping!

Postscript – this approach seems to work – if you keep the saucer full of water! The plant romped through 10 days with maximums above 36C and even a full week of maximums above 40C. It sadly didn’t survive not being watered by the designated waterer while I was away in February, so it dried to a crisp.

How the windows on a Cobra Lilly actually work!

The Cobra Lilly (Darlingtonia californica) is a truly unique plant endemic to the western United States of America (northern California and Oregon). It is closely allied to the Sarracenia pitcher plants, with both belonging to the same family (Sarraecniaceae). What makes it unique is its pitcher lid, which has been modified into a large, hollow hood. The opening is underneath the hood, immediately behind a spectacular fish-tail or forked-tongue structure. Looking at the pitcher from the front, it bears a striking similarity to a cobra reared up to strike.

The top of the hood is covered in many small windows that are almost clear (not white, like those of a Sarracenia minor for example). These windows are believed to serve a special function: disorientate insects once they enter the hood so they (i.) don't escape and (ii.) are more likely to tumble into the pitcher.

But do the windows actually work? I was out with the camera a few weeks back and happened to see a Polistine paper wasp trapped inside the hood. The below .gif animation is the result of photos taken at nearly 4 frames per second.

They windows do indeed seem to disorientate insects once they are inside the hood! I was first aware that something was inside the Darlingtonia pitcher because I could hear the scrabbling of it trying to escape. These photos clearly show the wasp trying to scrabble free of the pitcher through the hood where it is most strongly illuminated by the windows. However, in this instance, the wasp was a little too big, and it eventually managed to reverse out of the hole and escaped. You can see the wings of the wasp protrude from the mouth of the pitcher if you look closely.

I will take some decent photos of my Darlingtonia setup shortly and describe completely how I grow and propogate them.