I've always liked carnivorous plants but while I successfully grow other plants, I've been pretty good and not keeping the carnivorous ones alive. So, in the spirit of the Halloween season I thought I'd give it another try and make a nice mad scientist style terrarium.
This time I played twenty questions with some folks in the know and I think I may have figured out at least a couple things I was doing wrong. Either way I'm hoping my hungry little garden will at least last the season and maybe take out a few pests in the process.
The difficulty in this was more gathering materials than executing the project but I did at least one fun thing that was ind of interesting and I did learn a bit.
I also ended up writing a second Instructable after learning a lot about carnivorous plant potting soil. https://www.instructables.com/id/Potting-soil-for-carnivorous-plants/
Step 1: Materials
A large glass jar. Any jar should do. I chose one I can close up to actively manage the humidity.
There are certainly better blends than others and you can increase the happiness of your plants by using the correct mix. I just grabbed some basic potting soil. Again, this was a bad idea. Please see my carnivorous plant potting soil Instructable for a mix that won't kill your plants.
The plants. I went with a classic Venus Flytrap and an interesting Sundew. Probably could have used at least one more but I'm hoping they'll grow to fill in the spaces and I'm trying to encourage some moss as well. There's always time to add more if it looks too sparse.
Animal skull. I used a raccoon skull I picked up at the same shop I got my plants from but I have a growing collection of type specimens I've been collecting since childhood and then used extensively working as an archeologist. Best to not use something unusual. A raccoon was the perfect size and you can get them cheap on the internet if you can't otherwise obtain one.
Distilled water. Tap water or even bottled water will kill Venus Fly Traps and other bog plants. I'm told rainwater is OK as well and has been good for my orchids but I haven't tried it on this type of plant. Distilled water is inexpensive so there's no reason not to use it. Bottled drinking water often has salt added for flavor and will kill your plants and while chlorine is very bad for them it's not the only thing in tap water that will kill CP's. So setting it out over night won't help in this case.
Total cost if you go out and buy everything is probably around $40.
Step 2: Preparing the Skull
I thought it would be fun if the Fly Trap was growing out of the top of the skull. This required a fair bit of carving.
I used a Dremel with a cutting wheel. This creates a lot of very fine bone dust and in my case awful smelling smoke.
It is unwise to carve bone in this manor without a respirator. it's not good to inhale the dust and could be potentially dangerous beyond the obvious. I also broke a cutting wheel and sent pieces of it flying.
You can see from the photos I basically topped the calvarium and then cut out the bottom of the brain case. This was so the plant could grow all the way through rather than restrict the roots and hope the bone would eventually rot through. That can take years.
The roots are fairly shallow on many bog plants anyway but I also wanted it to be an extension of the soil column.
Step 3: Soil
I wanted this to be a bog in a jar. So, I didn't add stones or other material in the bottom. Just thought it would look nicer without and I can clearly see the soil water level either way. ...I did throw in most of the bone fragments from cutting the skull. The bone would later be confirmed to be fairly inconsequential and while a layer of gravel can help monitor water levels and a couple other factors it isn't essential.
I guessed at a balance between having enough growth medium and room up top for a healthy micro climate with room for the plants to grow in that direction as well.
The soil that came with the Sundew was pretty loose and fell apart quite a bit when I unpotted the plant so I mixed it in with the rest. The fly trap had to be cut out of it's root ball a bit to fit into the skull "planter" and I was careful to set aside the layer with moss growing on it. The roots of both were still pretty much covered in the soil they came in.
Nothing mysterious here other than my needing a CP friendly potting mix. Here's the link to that once again in case you missed it.
Step 4: Placement and Planting
I simply found decent placement for the plants and arranged them like you might in any other terrarium or container garden.
I mounded up the soil a bit under the skull and dug a nice hole for the Sundew.
The soil stays wet so things don't move around all that much.
Step 5: Initial Watering
The only thing to remember is that even gentle pouring can splatter the inside of your terrarium. No big deal, it wipes off but if you tip it at a slight angle you can pour a gentle stream down the side and avoid the mess.
You'll also want to do this slowly and give the soil plenty of time to soak up the water. Add too much and it's hard to get back out. You want wet soil but not mud or standing water. Just take your time and pay attention. Many bog plants are capable of living at least partially submerged for short periods of time but it isn't ideal and they will eventually die if left that way.
Again, resist the urge to use bottled or tap water if you haven't picked up some distilled water.
Step 6: Enjoy the Awesomeness!
I'm pleased enough with the outcome to already be thinking about other variations and daydream a little about more interesting and exotic bog plants. I've also kind of been interested in a full "vivarium" with both plants and animals and what mad scientist doesn't need a few Poison Dart frogs hanging around?
Step 7: Update: Re-potting and Dispelling Some Myths
In response to some very helpful advice I decided to re-pot my plants in suitable soil that they can continue to live in.
There were some very constructive comments and some people were kind enough to PM with concern about the health of my CP's. I'm happy to report planting them in regular potting soil will not kill them quickly. The wrong water and fertilizers will knock them out fairly quickly but the soil itself is a slower death and not at all a death sentence.
After conferring with some knowledgeable professionals including a couple botanists, a pro grower and a soil science guy I sorted out what constitutes good soil for these plants, what kills them and why.
After a week(it took forever to find the materials here in the city) waiting in regular potting soil my plants are re-potted and still thriving with no reason to think they'll croak. Death by bad soil can take several months and possibly longer if the soil profile is deep enough for the mineral content to leach to the bottom. Areas with high heat or low humidity where water evaporates quickly will have a much shorter safe window to correct a problem like this.
You can see the tear down and repotting in the images. So, now they have the things they need to thrive, sun, distilled water, acid soil free of minerals and chemicals and even a few lab pests to eat!
At this point if anything takes them out it'll be life in a smallish terrarium. Considering an arduino based hydro-thermograph as well, just to really track exactly what's going on in there.
Planning on setting up another terrarium or two and have the materials on order.
Thanks to everyone who helped out and shared their helpful comments!