Question
QUESTION: I live in coastal Southern California, USDA zone 10B. The coldest temperature I've recorded over the last 5 years was 43F, and that was only once - seldom goes much below 50F.

At the beginning of summer, I bought several Drosera rotundifolia from a grower in Alaska. He had collected the parent plants in the wild around Anchorage. The plants have grown well outdoors all summer, but now that the photoperiod is getting shorter, they are producing gemmae, even though the temperature is still warm. This is borne out by the seller, who said the plants only have about a three-month active growing period and are completely acclimated to the harsh Alaskan winter.

So, how do I handle them here in SoCal?

Should I just put them in plastic bags and let them sit in the refrigerator for nine months? Can they somehow be re-acclimated to our mild winter? If so, what is the best procedure? What are my options?

ANSWER: Hello Ted,

First off, I would suggest that your supplier no longer collect endangered species from the wild unless they have a recognized collectors permit or licensure. Drosera rotundifolia is endangered and can become extinct from such activity. While it is a species of least concern so far as being endangered, it still is on that list. There are plenty of suppliers to buy such plants from, as I have done. Sorry about the rant, but this is an important topic if we want these beautiful plants to remain alive in the wild for our children to see.

Drosera rotundifolia do not produce gemmae. What you are likely seeing are winter buds. Pygmy sundews, from Australia, produce gemmae. The photoperiod tells the plants that Winter approaches. Since the plants are used to very long Winters and short Summers, they are reacting to what they are used to. They will soon require cold temperatures until they begin breaking dormancy.

Whan a plant goes dormant or breaks dormancy, they will halt and begin growth at seemingly predetermined times. I kept my Sarracenias and Venus Flytraps cold and in low light for slightly longer than usual this time and they began growing slowly in cold temperatures around the beginning of Spring to show that they were ready to get back to the growing season. This indicates that changing a plant's seasonal cycle may be harder than expected. It may well be hard wired.

Most Drosera rotundifolia have a six month cycle, but those in Alaska sound like they are even more restricted in their growth cycle. You may have to go ahead and keep them cold and in low light until you see them trying to grow again. I never suggest refrigerators to overwinter your plants. They are simply freeze drying mold farms. I use ice chests and either frozen water bottles or cold packs for camping. It takes some work and diligence to do this. I place the plants in the ice chest, place cold packs or ice bottles around their pots, clip off dead or overhanging material, and then close the ice chest overnight. In the morning, I change out the ice/cold packs and leave the ice chest open all day and near a light source that will provide some limited light for the day (several feet from a window or florescent light source and only for about 8 hours a day). I keep thermometers around to ensure the temperatures remain around 35-50 degrees all winter whether the ice chest is open or closed. Once you get a feel for it, it is just a matter of replacing a certain amount of ice or cold packs around the pots every 12 hours. It may take 8-12 cold packs or ice bottles each period of replacement according to how many pots you have, how big the pots are, and how cold you need it to be. Just monitor the temperatures and keep it just above freezing and just below 60 degrees all winter.

Other than that, good luck. Drosera rotundifolia tend to be temperamental about seasonal cues and sometimes die off unexpectedly if things are not just right.



---------- FOLLOW-UP ----------

QUESTION: Perfect answer - you got the highest rating I could give.

1. As far as I know (didn't see the license, just his word), this was a registered collector, in business for some 30 years. I share your concern about leaving plants in the wild.

2. Thanks for clearing up my confusion about gemmae vs winter buds. The latter is certainly correct in this case.

3. Your ice pack method sounds tried-and-true, but is perhaps a bit more labor intensive than I am currently capable. I think, in spite of your advice to the contrary, I will put them in sealed plastic baggies in the refrigerator at night, then out in a low-light environment during the day.

If you wish, I'd be happy to report to you later how this experiment goes.

Thanks again for the excellent response.

Answer
Hello Ted,

Thanks Ted. Glad to see registered collectors out there. I had a College Professor that had such authority to collect wild exotic species.

You can try the refrigerator if you have room. It should work well enough if you remember to take the plants out every morning and keep them cool all day with some other method while they receive some light and air. I tried the refrigerator method to stratify some seeds and it took a couple years to finally get rid of all the mold problems I had with just that one batch of plantlets. I had no more mold problems after I started using the ice chest method for everything. The problem with the refrigerator is that most people do not take the plants out for air, light and a little water periodically. Their plants wind up dehydrated, black, and moldy like last years unknown left overs. I think taking the plants out for light and air helps alleviate the mold while the slight change in temperature from 40 degree night to 50 degree day simulates nature to some degree. When six to nine months are up, look for signs of growth and begin providing longer periods of more intense light. When they are ready, they will wake up and begin growing again. Then you can warm them up and see how they do.

Either way, there will be some monotonous work involved with keeping the plants alive through winter dormancy.

Once again, good luck.