What fun! This past year of watching innocent looking plant material gobble up great quantities of clueless insects and arachnids was so entertaining! It's difficult to make an objective evaluation of something with so much innate entertainment value. I'll try though. OK, where to start...
Basically, the design of the bog is working very well, some by design, and some quite by accident. First, though, let's discuss the shortcomings.In spite of these issues and difficulties, there are many positive aspects of the design. For example:
I'm not convinced the deep reservoir contributed significantly to any 'cooling' effect, and ultimately contributed directly to the demise of the Darlingtonia for which it was designed to support. Immediately, the reservoir began breeding mosquitoes. I then introduced three or four small 'mosquito fish' for control (Sing a couple of verses of "There was an Old Woman Who Swallowed a Fly" to get the idea of where this could go...). The open surface of the reservoir, being exposed to sunlight and the elements contributed to rapid evaporation and excessive algae growth. It was the nitrogen given off by decaying algae that killed the Darlingtonia. My original plan was for water pumped to the upper bog, at little more than a drip rate, to fill that bog and flow over the waterfall, soaking into the bog substrate on the lower level and eventually replenishing the contents of the reservoir. WRONG. The water pooled on the surface of the lower bog until it reached critical mass, then rushed, carving massive canyons through the soil, into the reservoir, dumping buckets full of peat and sand into the depths of the reservoir. The solution, which is masterful in its design (if I do say so myself!) solves several issues. The solution will be shared below in the design benefit section. The waterfall has to be filled in with gravel from behind. Slugs, attracted to the cool damp depths of the crevices between the rocks, are treated to a death by drowning when the water flows for an hour twice a day. Decaying slugs also are detrimental to bog flora and sensitive nostrils. This is a winter project. I'll get on it soon... I believe the volume of water in the reservoir may have diluted the acidity of the peat somewhat. I don't know this for sure, but it makes sense. The pH of the water in the reservoir is 6.0, considerably higher than the 4.5 - 5 that I was expecting. Dilution may occur this winter as rain water overflows the entire system and dilutes the water further. I'll be keeping an eye on it. The edge of the bog is too close to the lawn. Every time I run the lawnmower by I shower the sundews with massive doses of dust, dirt, bark dust, grass clippings, etc. It's too late to do anything about it , but next time... In my eagerness to have a fully mature and representative collection of plants, I purchased only adult plants. I'm suspicious that younger plants may have adapted more quickly and produced equivalent results within a year or two. It's difficult to know for sure.Water The reservoir serves to equalize and maintain the water in the system at a very consistent level. Oregon summers are randomly interspersed with long periods of very warm, dry days. Daytime temperatures can rise above a hundred degrees for several days in a row with humidity dropping to 20 - 30 percent. Evaporation in these conditions is significant, up to three gallons per day. The prospects of keeping 10 or more square feet of peat and sand damp in these conditions is daunting, to say the least. In spite of the incredible water retention properties of peat, it absorbs and passes new moisture at a similar rate. The reservoir served kind of as a 'reverse tray' method for watering. Instead of sitting a pot in a tray of water, a pot of water is inserted into a tray of peat. With the water level of the reservoir two to four inches above the bottom of the bog, a constant supply of moisture is supplied to the entire system. The correction to the waterfall problem was this - a channel was excavated from the base of the waterfall to the reservoir. This channel was then lined with porous underlayment material, the same material used to line the bog between the dirt and the plastic liner. It is a non biodegradable fabric that allows water to pass through, but is tight enough that sand and other material cannot penetrate. The channel was then molded to provide a small pool at the base of the waterfall, lined with plastic to help retain water, and then filled with gravel (including the pool, to reduce light penetration and provide a place for a bladdarwort to grow). This arrangement works spectacularly, in that with the twice daily circulation of water from the reservoir, the bog receives adequate watering even when the water level in the reservoir drops below the bottom of the bog. To control the excessive growth of algae in the reservoir I inserted a large pot into the opening to block light. I planted Japanese Blood Grass and Super-dwarf Cattails in this pot to absorb as many nutrients from the water as possible. Not only is this an attractive addition, but it serves to enhance the safety of the bog by covering an otherwise gaping homeowner liability issue. This design allows 'exotic' bog species to be seamlessly introduced into a general landscaping scheme. The self contained environment is easy to maintain, requiring only the regular addition of water and the periodic weeding.
No discussion of carnivorous plants is complete without a discussion of water supply. Virtually all carnivorous plants require distilled water. Replenishing three gallons of evaporated water a day with bottled water from your local drug store is prohibitively expensive. An inexpensive source of bulk distilled water is a must. I tried an inexpensive reverse osmosis unit initially, and was unable to obtain satisfactory results. I believe low water pressure may have been a contributing factor. The unit came highly recommended from a reputable dealer, it just didn't work out for me. I built my bog with the expectation of using water from the RO unit.
Now it's time to panic. With visions of a quadruple-digit water bill dancing in my head I began collecting rainwater off the roof of Rocky's (our staffordshire bull terrier) run and storing it in 5 gallon buckets. I was able to collect and store 50 gallons of water before summer hit. As my water supply began to dwindle I began calling every water supplier listed in the Yellow Pages ("You want how much?" "Are you sure you want distilled water?" "What are you doing with it?" "We don't actually have distilled water. It's very high quality spring water. Tastes real good!" "Distilled water is $1.95 per gallon" "Sure, we deliver. That's a 200 gallon minimum... um, let's see, that'd be $420"). Finally, I located a local food processing plant that produces its own distilled water and sells in bulk to the general public. I was able to purchase pure distilled water for 1.70 per 5 gallons - U-haul, U-provide-the-buckets.
I made a total of five trips across town with my 10 buckets bringing my total water bill for the summer to $85. This was a fairly average summer for rainfall. A drier summer might not be so much fun, as it's a 20 mile trip each way to the water store. I'm now investigating putting rain gutters on the shed and purchasing barrels to collect rain water. This investment would take a couple of years to recoup, but might be worth it in the long run. Considering the time to drive to the water store, the environmental impact of driving my vehicle that far just for water, and the energy used in the distillation process, there's probably no good reason not to install a catchment system.
OK, so the whole concept is a little perverse. Deriving pleasure from watching a housefly plummet to the bottom of a narrow tube to be slowly digested by enzymes secreted from the wall of the plant is a bit morose. But, it was a housefly. Probably the same one that derived it's own perverse pleasure from tormenting me over my picnic dinner earlier this evening; and the craneflies and moths that eat my lawn, the yellow jackets and spiders that otherwise disrupt my otherwise civilized domestic life. It's all rather gratifying, in a twisted sort of way.
I will admit that the wiggling legs of a spider or crane fly hanging out of a tightly closed venus flytrap is a bit much. Sometimes the two or three day struggle of a hapless insect attempting to escape the progressive grip of a sundew is mildly distressing. There are the obvious ethical issues that arise from introducing these bug eating horrors into an environment previously devoid of such snares. It's not fair, I know. I suppose I should have also imported 'carnivorous plant aware' insect species to avoid accusations of entrapment.
In spite of somewhat twisted entertainment values, the opportunity to observe firsthand one of the more unique aspects of the plant kingdom is fascinating. I have been amazed by the volume of myth and misinformation circulating the general public regarding carnivorous plants. I have had many opportunities to discuss the biology and ecology of not only Sarracenia, but the value of wetlands in general and their importance in many ecological systems.
The Weather and the Future
As this summary is being written in early December, 2000, the bog as already experienced night time temperatures in the mid to low twenties for a two week period. Temperatures have never remained below 40 for an entire 24 hour period. The bog is currently protected beneath a four to six inch layer of pine needles. This mulch layer was laid down after two or three consecutive frosty mornings. Young, tender pitchers were the first to succumb to the frost. Others, however, have persisted and seem to be thriving even in these conditions. Most notably, S. leucophyla presents a rather striking image amongst the dead and dying annuals nearby. S. x Judith Hindle is doing remarkably well, as is S. purpurea venosa "Burkei". S. psittacina is covered by the mulch and appears to be doing well. The tiny pitchers froze last spring, but this year's pitchers seem much more tolerant. The sundews are all dormant, and it remains to be seen how many of them survive the winter. D. rotundifolia will, but I have my doubts about D. binata and filliformis. I have good reason to expect the survival of the venus flytraps, though each frosty morning does make me a bit nervous.
Winters here can be erratic. The winter of 1999/2000 was extremely mild. We received plenty of rain, but freezing temperatures only on two or three occasions in early spring. This winter has already been much colder and much drier, and winter isn't even here yet. The possibility exists, supported by historical evidence, for extreme cold (near zero), several inches of snow, freezing rain, and flooding rains. Typically, severe conditions can repeat for several consecutive years, followed by years of mild conditions. Fortunately, severe events are usually short-lived and milder conditions prevail. In comparison to the native habitat of Sarracenia in particular we are a little cooler and wetter, but rarely do average conditions in the Willamette Valley of western Oregon exceed extremes of even the Gulf Coast.
So, what does it all mean? I believe, short term, that my bog is a success. Anecdotal evidence suggests most bog plants are more hardy than sometimes given credit. Long term survival will result from a combination of constant care, careful analysis of data, and a little luck. I'm through the easy part. Continued careful observation and attention to details are essential for the continued success of this project. And, maybe, if I do my job right, others can benefit from my experience.
Carnivorous bogs as a 'mainstream' feature in urban landscape design is probably not going to happen. While actually easier to maintain than the average home water feature of Koi and water lilies, you do have to spend a great deal more effort explaining yourself. One possible option is to build a more traditional water feature as a decoy and only tell your closest friends and enlightened observers about your 'real' water feature.
This is the first in what I hope will be a continuing series of documentary presentations on my experiences as an amateur boggist. I will attempt to share everything I feel is important. Until next year...