Intro: Growing a Venus Fly Trap Indoors in a Dry Environment
I've been interested in carnivorous plants since I was a kid, but I haven't had any for about a decade. Recently, though, the idea of growing a venus fly trap in my dorm room hit me. There were a few issues I had to overcome before growing one, though. There are three major environmental factors venus fly traps require: high humidity, lots of light, and a nutrient-poor soil watered with distilled water. The soil is an easy problem to solve. Humidity is a bit trickier, but even in a place a mile above sea level as long as the terrarium has relatively small openings for air the humidity stays high enough inside. Light is another big issue. I don't a whole lot of sunlight through my window, so I integrated an LED light source into the terrarium. I have it running on a timer 10 hours a day, so between this and the sunlight I think it's getting the rough equivalent of a day of direct sunlight.
Step 1: Design
I designed 6 interlocking panels in SolidWorks that together comprise my terrarium design. My design calls for the sides to be laser-cut from 1/4" acrylic. The interlocking design gives it a cool look, makes it a lot easier to glue the terrarium in the right shape, and gives it a better seal when complete.
Step 2: Laser Cutting
I used a 100-watt Epilog laser cutter my college has to cut the panels from 1/4" acrylic. The design was intricate enough that any other cutting method would take longer and not give as nice results. Using the laser cutter, the panels came out with very clean, accurate lines. This made the final terrarium look very nice and helped the pieces interlock correctly when I glued them together.
Step 3: LED Light Source
In the solid model design of the terrarium, I designed a 5X5 grid of 5mm holes in the top panel. I bought a bunch of white LEDs off eBay and glued 25 of these into the holes. By folding the leads of the LEDs down and soldering them together, I wired all of the LEDs in parallel. I wired up this circuit to a 5V phone charger I had around. It would be good engineering practice to wire these LEDs in series with the LED circuit to drop the voltage across the LEDs, but because there are so many LEDs they can handle this kind of voltage without burning out. I plugged the power supply into a timer so it automatically runs for 10 hours a day, hopefully giving the venus fly trap enough light.
Step 4: Assembly
To assembly the terrarium I glued the panels together with Devcon Weld-it. It is a waterproof, flexible glue that dries clear, bonds plastic, and dries quickly. The catch is that it's super toxic, highly flammable, and emits a lot of nasty volatiles when drying, so I had to be really careful using it. With the interlocking design of the panels, I had to be aware of which surfaces would be contacting when glued, and make sure to spread glue on all of them. I glued two side joints at a time, then glued the bottom on. I taped it together to ensure that it would dry in the right shape overnight. I then ran a bead of glue along each inside seam. Even after all this, there were still one or two leaks, but I was able to seal them easily enough with a drop of glue. After a few days of containing moist soil, there don't seem to be any leaks, so the terrarium seems waterproof.
Step 5: Getting the Venus Fly Trap
Believe it or not, you can buy venus fly traps online. I've bought two of them this way, and they seem to survive the shipping process pretty well. The two websites I've used are:
The plants from Predatory Plants seem to be a bit healthier and older, but the Fly Trap Shop has a bigger variety, so it's a trade-off. The one I got for this particular project was from the Fly Trap Shop because they were the only ones with the Akai Ryu cultivar in stock. I didn't know this until I started researching venus fly traps recently, but there are a lot of different breeds available (when referring to plants, they like to call them cultivars). The Akai Ryu (red dragon) cultivar, shown below, is red rather than the traditional green. In the pictures, you can see that mine is green, hopefully because it's still young and not because they sent me the wrong kind.
Step 6: Planting
Venus fly traps require some very specific planting conditions. They need soil that has zero nutrients; they're evolved to live in a nutrient-poor environment and derive nutrients from the insects they eat. They also need to be watered with distilled water, as the nutrients in tap water build up over time and can be hazardous. I suspect that purified bottled water (not spring) will work as well, but I've only ever used the distilled water you can by in gallon jugs at grocery stores. I took a mixture of 1/2 peat soil and 1/2 pearlite, soaked it in distilled water in a ziploc bag, and spread out a layer in the bottom of the terrarium about an inch and a half thick. I made a hole to the bottom and