Carnivorous Plants/Watering from top/tray
JP, once again :-)
I have a question about the watering of carnivorous plants.
What is it exactly about the thing to water from top, others from tray. Does it matter so much? Surely, Drosophyllum wonīt like watering from top, but how about Sarracenia, Flytraps, etc.?
I have been told that it is rather critical to water from tray in winter because of fungal risks when watering from top. Is there any other reason, and does it make a difference for the growth of the plants?
I mean people with mini-bogs canīt water from below too for example. And is this "water from trop/tray" method to be taken different when talking about indoor or outdoor plants?
Thank a ton Jeff and have a great weekend!
Warm regards from Germany,
This is one of those areas where you need to think more conceptually, and think about what happens to particular plants in nature.
Let's take tray watering. This is simply an efficient way in cultivation to maintain consistent soil wetness for bog species that are used to being wet all the time. It can vary much from plant to plant as to how wet they would normally be in nature. For instance, S. purpurea ssp. purpurea and S. flava are used to being quite wet, often right at the water's edge or on floating sphagnum rafts. Drosera intermedia's nickname is Water Sundew, and when I saw them in North Carolina they were often in a shallow amount of water. Other plants, however, such as Venus flytraps, other Sarracenia species, Drosera rotundifolia are in damp conditions, but usually not sopping wet. Having a pot sit in a tray of water is just an easy way to maintain the wet conditions. You can adjust the water level for plants that don't like it as wet, such as Venus flytraps.
Now, if labor were no issue, it would be better for most plants if they didn't sit in water in their pots, and you top-watered them every day. This is more like nature where they get rained on lots. This works with big containers like large planters (mini-bogs) that can hold onto lots of water in the soil, but falls short with pots that can dry quickly in summer. Top watering aerates the soil and keeps roots healthier in the long-run. It's common for pots that are tray watered to get an anoxic layer in the bottom of the pot that is in water during warm weather. Plants often won't grow their roots into that.
Let's talk about that fungal issue. The biggest things that contribute to Botrytis in Sarracenia in winter is low light, and lack of air circulation. If you have both of those conditions, like you would in a greenhouse or keeping them indoors, or if the plant has masses of dead leaves that haven't been trimmed, keeping the crown of the rhizome wet would help the fungus. However, if you have plants outside, they are getting rained on, and they have exposure to wind and UV light these things wash away fungal spores and keep the little nasties at bay. If because of climate you have to keep the plants in a greenhouse or cold-frame, then you do have to treat them different, and take measures to prevent the fungal growth. I've lost far more plants in greenhouses than I've every lost outdoors.
I've been talking more big picture here, but let me address some of the things you've heard directly.
Mini-bog; they can totally be tray watered. You just need a big enough tray. We have several of our speciment plants set-up like this.
Tray watering crucial in winter? This is so situational. In a greenhouse I actually try to make sure there isn't too much water in trays because the long periods of wetness an increase mold along with the low light and lack of air circulation. Plants outdoors it doesn't matter too much one way or the other. We have hundreds of Sarracenia sitting is shallow water pools in winter outdoors along with a couple of big planters that just rely on rain. The plants in the pools do fine, we just have to watch to make sure drain holes don't get blocked and the pools flood. Since we have so much rain in the Pacific Northwest in winter (well, except for this year), plants are constantly being refreshed from the rainfall. If you seem to be getting more fungus in your particular situation, then pre-treating with a fungicide for winter, and removing as much dead material as possible is important. Top-watering in of itself isn't bad, it just depends what else is going on. It's in fact, very good for the roots.
Drosophyllum. Top-watering is exactly what you want to do, and I'm emphatic about this. You don't pour water on the plant, but you water the soil until you get runoff, then stop. A little water in the tray is ok, especially in summer. In winter, however, you don't want much water in that tray or root rot is almost certainty. With Dewy Pines you really have to get into the habit of feeling the soil. Feels a little moist? You're fine. Leave it alone. Feels real dry? Time to water. Make sure any water in a tray is used up before watering again. In summer you can be a little more sloppy with water since they are using so much. In winter you have to be more careful.
Hope all this helps. It's not a real "one size fits all" subject.