Let’s talk about ferns for a bit. Anyone working with terraria or miniature gardens eventually has to deal with ferns, both accidental and deliberate. In cases where they’re deliberately introduced, it’s because their foliage or other habits. Maidenhair ferns (Adiantum spp.), for instance, are an excellent addition to prehistoric-themed miniature gardens because of their ginkgo-like appearance and their extreme hardiness: so long as you don’t let them dry out, they’re nearly impossible to kill for long. Because they reproduce from spores that may remain dormant for years until the right conditions ensue, or the spores blow in on a breeze, accidental intrusions happen on a regular basis. Orchid enthusiasts using long-fiber sphagnum moss, particularly the light-blond LFS from New Zealand, discover all sorts of additions popping up after their sphagnum gets a bit of light, and some of these can be more visually stunning than the plants that grow alongside them. After all, the invention of the original Wardian case was instigated by a serendipitous fern sprouting in an unexpected situation.
So what’s the problem, you may ask? It’s that ferns in a miniature garden, terrarium, or vivarium environment tend to be a bit, erm, aggressive in their growth. Left uncontrolled, one seemingly inoffensive fern sprout can take over large enclosures and choke out smaller plants. Many species have long, tough roots that wrap around features, sink into ceramic pots, and make enclosure maintenance nearly impossible. At the bare minimum, that one fern can spread past its intended area, requiring constant maintenance to keep it under control. If an enclosure has a particular look that needs to be maintained to emphasize a particular plant, ferns have a tendency to crash the party and laugh at attempts at eviction. In extreme cases, the only viable option is to tear out everything and start from scratch…and then go through the same routine again and again.
Now, ferns can be controlled in the miniature garden the way bamboo can in standard gardens: by putting them in containers so their roots don’t sprawl and new shoots don’t spread. On a basic level, any material reasonably impermeable to plant roots could work, such as metal, glass, or stone. In miniature gardens, especially those with acid-loving plants such as orchids or carnivores, metal tends to corrode and contaminate the whole container, while glass and stone have their own problems with weight and porosity. The idea is to have something with an impermeable side but a permeable bottom, so moisture can wick up into the container from its surroundings while preventing fern roots from punching through. Equally importantly, it should be something reasonably attractive or possible to make attractive, if only so viewers don’t focus on the container instead of the fern inside.
The good news for anyone looking for good fern excluders is that they’re sometimes a bit too common. One quick trip to the grocery store, and your house is full of convertible fern containers. Food, drink, hair care, skin care: if it’s plastic and can be cleaned, it has potential. Even better, because of the demands by marketing to produce packages that are as uniquely identifiable as their labels, many of those are exotic enough that with a bit of modification, most would never recognize a final container as such. A bit of poking through the recycling bin, a good washing, and you have the beginnings of a fern excluder.
Before starting, consider the container that you’re converting and what kind of fern it is intended to hold. Tall containers have a problem with prematurely drying that requires additional top-watering, and with becoming top-heavy as big ferns get established. Overly small containers will restrict bigger ferns to the point where the plants will send roots over the side in search of water and nutrients. The container’s place in the terrarium or miniature garden has to be considered as well, because unless the fern is the only thing intended to be displayed, its excluder could overwhelm everything else. If possible, test the placement of the final excluder by putting the container in its intended location. If it doesn’t work for what you’re intending, there’s nothing wrong with going with another container and saving that one for a future project.
Converting a spare plastic container into a viable and usable fern excluder is done in three stages, two of which need tools or other accessories. In the first stage, some sort of knife is essential, with a drill and various bits, pliers, and medium-grit sandpaper being extremely handy. Since you’re cutting plastic, make sure that the knife is as sharp as possible, so using a razor knife or box cutter with replaceable blades is highly advised.
WARNING: Cutting plastic containers can be dangerous, both due to blades binding in the plastic and blades breaking during use. When cutting, cut very slowly to keep control of the blade, and ALWAYS cut away from your body. Cutting on a protective surface is highly recommended, and the use of scalpels, break-away hobby knives, and other thin blades is NOT recommended. If necessary, wear gloves when cutting plastic containers.: both the blades and the resultant cut edge are very sharp.
To start, remove any paper or shrinkwrapped plastic labels from your container. Paper labels can be removed by soaking the container in soapy water for an hour and then scrubbing, and commercial sticker-removal products such as Goo-Gone will work on any remaining adhesive. With plastic-wrap labels, just cut these with a knife and peel them free.
Some containers need additional work for cleanup. For instance, my bicycle route to the gallery is often strewn with empty BuzzBallz, which make excellent fern barriers due to the container’s size and thickness. The only problem with them is the aluminum top, which needs to be peeled off with pliers before further work can be done. (WARNING: metal edges can be sharp. Don’t do what I did: wear protective gloves and eye protection when peeling off metal attachments and save some bandages for later.)
Now, if your container already has the general look you want, then great. If not, you may have to remove the neck to remove screwcap threads and the like. With most containers, a razor knife works very well: start with an initial hole (a drill or nail hole works well) and then SLOWLY cut around until the neck is detached. With thicker-walled containers, saws designed for plastic and rotary tool cutting discs may be necessary: follow all safety instructions for these tools when using them, and work slowly to keep control and to keep friction heat from re-fusing the plastic while cutting.
For various reasons all involving weight distribution and structural integrity, the bottoms of most plastic containers are considerably thicker than areas near the tops. (The next time you accidentally drop a bottle of vegetable oil or salad dressing and it bounces instead of rupturing, say a silent prayer to the packaging engineer who successfully convinced Management that an additional gram or two of plastic resin per bottle was a necessary cost.) This means that razor knives won’t (pun intended) cut it. You have many options for electrical augmentation, but a cordless drill and the appropriate bit usually gets the job done in my case. A few warnings:
Numero Uno: Anyone who took a shop class in high school, who took any remedial home repair class in adulthood, and any fan of the Canadian version of Doctor Who will tell you the same thing, over and over: never, ever, EVER hold anything intended to be drilled with your hand. (Everyone will say this, of course, but the ones that paid attention don’t have those distinct scars that say “I figured that I was smarter than the drill press.”) Since most plastic containers are too flimsy to be locked into a vise for drilling, it’s time for alternatives. In my case, I use an old towel, usually with a silicone sheet inside for extra grip, to hold the container in place without actual flesh connecting with the plastic if that plastic starts spinning out of control.
Numero two-o: because of the way most of the world’s plastic containers are made (check out some Baby Soda Bottles one of these days), the absolute center of a plastic bottle is often convex instead of concave. This means that if you’re starting with a large bit, keyhole saw, or other drill-based cutting tool, that spinning tool is going to spin off true, possibly biting into the plastic in a place other than where it was intended or even into a nearby hand. To get more control, start out with a much smaller drill bit, or even a sharp nail or punch, to make a starter hole for the larger bit. If you need to do multiple borings until you get the correct-sized hole, so be it: this work isn’t going to be graded on expediency.
Numero three-o: if at all possible with drills or other cutting tools, try to go with maximum torque and minimum speed. The reason is that as it’s spinning, the drill bit will generate enough heat from friction to soften the plastic it’s cutting. The plastic can jam up the drill bit, re-fuse as soon as the bit stops, and even give a good burn to unprotected human skin. Even with going slow, some melted plastic will collect along the edges of the hole, and the final hole may not be completely cleared. In that case, use a stout blade, slowly and carefully, to cut out any rough plastic from the edges of the hole.
Finally, when this is all done, you’ll want to smooth out the holes at either end of your container with medium-grade sandpaper. In particular, decide which end is going to be the bottom of your fern excluder and use the sandpaper to even out that end as much as possible. It doesn’t have to be perfect: it just has to be even enough for the next stage. While you’re at it, rub that sandpaper over the whole of the container: this gives a rough surface, referred to by artists as “tooth,” to give adhesion for what you plan to do next.
For the second stage, you’ll need a different set of tools and supplies. The essentials include:
- Silicone sealer, preferably aquarium grade
- Landscape weed barrier cloth
- Scissors suitable for cutting cloth
- Primer paint
To start, cut a square of weed barrier cloth slightly wider on each side than your container. Set it on a flat surface, preferably covered with baking parchment or wax paper.
Next, after determining which end of your container is the bottom, put a good thick coat of silicone sealer all over the edge. Don’t worry about it being a bit sloppy: this part will be underground when you’re done.
Take that freshly gummed-up container and press it bottom-down atop the weed barrier cloth. If you want to smooth the bead of fresh silicone, use tongue depressors, caulking tools, or a gloved finger to clean things up (don’t use a bare finger unless you like cleaning silicone from your skin for the next few days), but make sure that the bead runs over the entire outside of the joint between the container and the cloth. After this is done. set it aside for about 24 hours to allow the silicone to cure.
Next, the container needs a coat of paint for three reasons. Firstly, unless you specifically want a clear fern excluder so you can see roots and plantlets growing inside, you’ll want to hide the excluder’s humble origins with a bit of color. Secondly, if the bottle had its label printed directly on its surface instead of on a label, giving free advertising to the original manufacturer may not be desirable. Thirdly, a good coat of primer for plastic makes an excellent base for subsequent embellishment. For the last ten years, I have had excellent results with Rust-Oleum Universal spray paint: it’s an excellent primer that doesn’t attack most plastics, it tends to cover a surface in one pass, and it comes in a wide range of colors and finishes, including hammered and metallic effects. For most miniature garden and enclosure applications, I very highly recommend the Carbon Mist because it gives the impression of shadows without slipping into “complete endless void” in smaller scales.
After letting your primer dry for at least 24 hours, it’s time for further embellishment. If you want to highlight features on the original container with further paint, go for it. If you want to add features by attaching greebles, add texture by gluing on sand or aquarium gravel, or slathering it with silicone sealer and then pressing in long-fiber sphagnum to encourage sphagnum moss growth on the outside, knock yourself out. If you’re feeling particularly adventurous, add a layer of plumbing-grade epoxy putty to the outside and sculpting bark to make it look more tree-like. (I personally swear by Smooth-On’s Habitat epoxy putty because it’s safe for fish, amphibians, and reptiles.) If covering it with so many styrene parts and embellishments that it could double as a Warhammer: 40,000 game obstacle is what moves you, do what thou wilt. Just take into account three things: stability, weight, whether the item might rust/corrode/otherwise contaminate the surrounding soil, and whether the additions you plan to add will handle longterm exposure to sunlight. Other than that, whatever works is what works. When you’re finished, trim back the weed barrier cloth to make it easier to plant in an established miniature garden, or leave it as an anchor in a new one: it’s completely up to you.
After everything else is done. it’s time for Stage Three: The Planting. At this point, start adding your choice of planting medium into the fern excluder through the hole in the top. Pack it in gently so you don’t damage the weed barrier cloth at the bottom, and watering it regularly during the packing process helps settle the medium. In this example, this excluder is full of milled sphagnum moss for inclusion in a carnivorous plant enclosure. Just take into account that since the weed barrier cloth is porous, don’t add anything to the planting medium that might affect plants nearby, such as salt-based fertilizers for a fern in a carnivore enclosure.
When filling the fern excluder, don’t fill it completely. Leave just enough of a space at the top to add your fern, its roots, and any growing medium around those roots. It’s going to be stressed enough with its new conditions, so keeping the fern’s roots from being mashed or bruised will increase its chances of survival.
Finally, get your fern. Take a good look at its root system, and scoop out soil from the fern excluder to give enough room for those roots. Press it in gently, and scoop some soil alongside the roots to cover them. Give it a good watering, and it’s ready to be added.
At this point, add your new fern excluder where you need it, and check to make sure both that it’s close to the water level in the miniature garden or enclosure and that it’s stable. Placed correctly, water will seep through the weed barrier cloth from outside, encouraging the roots to go deep for moisture and discouraging growth through the rest of the area. This will discourage growth but won’t stop it, as many species will run roots down the sides and into surrounding soil. Trimming roots as they form is an option, and another is setting another fern excluder, wider and flatter, underneath the first excluder to facilitate those hanging roots. The fern excluder also won’t do a thing for new plants growing from spores, either from that fern or ones that blew in from elsewhere, so always check for new growth before it gets out of control. If you like that new growth, well, you’ve made one fern excluder, and there’s no reason why you can’t make more, right?
