Carnivorous Plants/Live Sphagnum Moss Top Dressing
QUESTION: Dear Jeff, Farin,
I am growing Sarracenia and Dionaea outdoor in large pots with growing life sphagnum on top. The moss has grown, and partly covers a bit the rhizomes.
Now in Germany autumn has come fastly since this week, temps. drop to 6-7C° at night, max. 16-17C° in the day.
My questions are the following:
- Should I set rhizomes free from the sphagnum?
- Is sphagnum, especially while dormant, really helping against botrytis/mold issues (as long as I donīt water to much of course)?
- As the moss is covering the whole pots, can I suggest that the soil is moist enough, if the moss is moist? Or should I remove moss around the rhizomes to have a better feeling about soils humidity during the dormancy?
Merci and have a nice day!
ANSWER: Hi Jean-Paul,
For your Sarracenia leaving the sphagnum on the pots is fine, and beneficial. Sphagnum creates a very acid environment so it helps inhibit fungi. Sarracenia are often found growing in sphagnum in nature.
For your Venus Flytrap, do pull away a little from the crown of the plant if it seems to be choking the plant. It can over time crowd them, but it's usually not a problem.
If your plants are outside for the winter, and getting rained on regularly, botrytis is seldom a problem. The combination of UV light and the constant flushing action of the rain tend to keep it at bay. It's a very real concern if plants are going to be in greenhouses or in a cold frame. A fungicide pretreatment is recommended for that.
You really don't need to worry too much about how wet or dry you're keeping the plants as long as the water levels in trays are not too deep. Our plants are constantly wet all winter with water levels no more than 1/4th the way up the pots. If you're getting adequate precipitation during the winter, you wouldn't have to have pots standing in water, you just need to make sure they don't dry out. Either way works just fine.
---------- FOLLOW-UP ----------
QUESTION: Hi Jeff,
actually tonight I thought about my question again, and I have a follow-up for it since I am very aware/worried about getting any botrytis infection!
What exactly will trigger the grow/appearance of botrytis? Is it the high humidity combined with low light, when indoor, or rather the wetness of the soil? Maybe the lack of air circulation indoors?
So if I understand you right, I can just keep my dionaea and sarracenia outdoor as long as the temperature doesnīt drop down below 0 C° (freeze) and I water enough? The amount of water in the soil, when outdoor, doesnīt matter either??? There is no "too wet" then?
And last but not least, as I mentioned previously, I have live sphagnum growing on top of the soil. Could it happen that botrytis sets on the soil/plant, although it is under the sphagnum, or would it always appear on top of the sphagnum first?
Thank you for your comments, I really appreciate it and it helps to understand the whole better!
Low-light combined with lack of air circulation, along with a food source such as dead leaves or other detritus is what is a breeding ground for botrytis.
Preventing botrytis key points:
1. Good hygiene. Clip off dead or dying leaves on Sarracenia. Be ruthless. The plants will grow new ones next spring. In December or January we cut off 90% of foliage on Sarracenia. This is especially important with heavy clumpers such as S. rubra varieties and their hybrids. I'm going to be super clear on this point, and I don't care what you read or hear from anyone else, it's better to remove foliage than not. Exceptions, S. purpurea and S. psittacina. Be more selective there since those varieties since they do capture some insects during the winter in milder winter climates. It's also ok to leave the phyllodia on S. flava and S. oreophila and their hybrids.
2. Light and Air/Water Circulation. This is the advantage of having plants outside in milder winter climates such as yours and ours. The UV light kills fungi. Wind and rain keep spores from getting settled. If you've clipped dead material off of the plants, the mold spores won't have much to get started on, and the rain and wind will wash them off.
I also checked weather data for your area, and temperatures are very similar to us here in the Pacific Northwest of North America. We have more rain in winter. You're more humid in the summer. North American carnivorous plants are perfectly capable of handling frosts. You just need to protect them during extended spells below freezing. If you have our volume #1 DVD you've seen the pictures of winter, and the chapter on protecting them. Our outdoor plants freeze every winter, but they are covered during extended cold periods. Covering is then removed once temps. are above freezing.
3. Spray with a fungicide if plants need to be enclosed during cold periods, or they are in a greenhouse for the winter. This is done as a preventative. Once plants are infected it's usually too late. We prefer sulfur based fungicides, but other types will work. Just avoid copper based fungicides. http://www.youtube.com/watch?v=gfVUrMaGjVs
4. Divide plants in the spring that form heavy clumps. This is most important with S. rubra and S. purpurea venosa. These are the two species we've found most prone to botrytis. This is simply going back to the good hygiene.
To address your other question about sphagnum, botrytis can start under it, but when you have a good crop of live sphagnum the very acid conditions don't give it a very favorable environment. I've personally never seen the mold growing on live sphagnum. Dead/dried long-fiber sphagnum is a different matter.
On wetness, both Sarracenia and Flytraps are bog plants. They are very wet in nature. Venus flytraps grow in very sandy soil, however, so that is the best way to moderate their soil wetness. Most Sarracenia grow in very wet conditions in permanently wet soil, or even floating sphagnum rafts in some cases. Our general rule is tray system, set plants in water, but no more than 1/4th of the way up the pots. Don't flood them in cultivation. The are this way sometimes in nature, but it is always circulating water which is very different. As I mentioned before, they don't have to stand in water if you are good about top-watering them, but tray systems are simpler.