Passive Solar Greenhouses
Permaculture Tour 2012 is Here
Plant Polycultures-A Garden with Many Functions
When designing a food-bearing landscape, one of the first things to decide is what plants will go where in the growing space. Most of us have heard of companion planting, square-foot gardening, perennial food forests, and inter-planting. Creating a polyculture combines many of these strategies and more. In this issue we will look at the planning stages of a polyculture and the elements necessary in creating a resilient and productive one.
In books and all over the internet, we can find loads of advice on which plants grow well together and which ones do not. Some of these combinations work fairly well, while others have yet to convince me. Providing mishmashes of different vegetables is not our purpose here. Since climates, pests, soil types, and our own tastes vary, we want to discover what works well in our own gardens, and we can do so by choosing plants not by species, but via the function they perform in the landscape.
Keep in mind that perennials are very useful in a polyculture. We can plant only annuals, but this is asking more much more work in the long run. Here is a list of functions (not necessarily in order of importance) that we want to include in any polyculture. A quick web search under any of these topics will provide numerous plant types suitable for any garden. If we have balanced proportions of plants in each of these categories, we are off to a good start:
A. Nutrient Accumulators
The thick and/or long roots of these species plunge far into the earth to extract minerals and other ingredients necessary for all plants to thrive. Usually after several of these species have matured, they will begin a natural decline in numbers once their job is complete. Examples of these might include: plantain, alfalfa, dandelion, chicory, and mustard species.
B. Nitrogen Fixers
In any guild, it is crucial to have plants that fix nitrogen in the soil. These plants have a specialized ability to extract nitrogen from the atmosphere and place it into the soil. Nitrogen is a necessary element in all plant development and speeds the growth of all plants. Nitrogen fixers include plants such as clover, peas, potatoes, Siberian pea shrub (caragana arborescens), lupines, and any leguminous or bean type plant.
C. Mulch Plants
We use these plants for building soil, preventing erosion and evaporation, and protecting and shading the roots of others. In this category we often might include a process called “chop and drop”, which involves cutting the plant down at the soil surface and leaving the greens on the soil to eventually decay. The roots either come back as another plant, or decay as well becoming part of the humus layer of the soil. The “chopped” parts of the plants also become a thick and fluffy layer on top of the soil. Some examples for mulch plants are rhubarb, nasturtiums, Jerusalem artichoke, mustard, oats, and barley, and virtually any soft-leaf plant that decomposes quickly.
These are any plants that will attract beneficial insects to your site (insects that will either pollenate to produce fruit or will consume/deter pests). Insect attractors include dill, coriander, thyme, yarrow, fennel, and believe it or not, dandelion.
There are other smaller categories, such as those which provide animal habitat and those which act as soil fumigants, but beginning with the four listed above is a good start.
Additionally, it is wise to use any plant that is able to perform more than one of the above jobs. This is what we call ‘stacking functions’. Examples of this would be using clover as both a mulch plant as well as a nitrogen fixer, or growing comfrey as a nutrient accumulator and to fix nitrogen or even using rhubarb as a mulch plant and of course a human food.
Finally, we should keep in mind the actual space each plant takes up in the landscape—both above ground and below. This is why we try to arrange plants in a polycultured landscape, creating a ‘mosaic’ in which generally we keep similar plants away from each other as much as possible. Doing so will minimize competition for sunlight and soil, as well as confuse pests (or at least keep them confined to one or two plants.) As in any form of permaculture, the more functions we can cover off each time, the more resilient the system and the less energy it will consume in the long run.
Passive Solar Greenhouses Beginning to Appear in Calgary
Many people protest the short growing season in Southern Alberta. With some techniques such as raised beds, cloches, and mulching, we can usually expand the less than 110 frost-free days, but some people are taking things a little further. A passive solar greenhouse can expand the growing season by several months without the use of external power. Unlike traditional greenhouses, the idea here is to trap solar radiation within the structure to create the appropriate growing conditions for most plants. So how is this accomplished? Think of what happens when we leave our vehicles parked for a while on a sunny day. Even on a day reaching a mere 15 C, the interior can be quite hot. This is because the glass allows the solar radiation to enter, while the rest of the car absorbs this heat and insulates against heat loss. Most greenhouses lose heat through any side of the structure that faces away from the sun. What we are trying to accomplish with the passive solar type is to minimize heat loss. To do so, the north and sometimes east and west sides are built with walls containing good insulating materials—sometimes with an R-value greater than most homes. On the opposite end of the scale, adequate ventilation is a must especially for the warmer days of summer. There are many other modifications that can be made, such as the angle of the glass and materials used as well as covering the whole structure with insulated blankets in the coldest days of winter. Nevertheless, experimentation with capturing and holding heat and moderating temperature so that plants might one day make it through our severe winters, continues. The following are links to a couple that have popped up in Calgary. (I also have a friend (no link yet) who has just installed a solar heated shower in hers).
Verge Permaculture, Just completed the addition of a rocket stove to this one…
This one by Joshua Baker of Radicle Routes was constructed using reclaimed materials…
Calgary Permaculture Tour 2012 is Here
For those not already in the know, on Sept 1, 2012 Prairie Sage will be conducting a one day tour of Calgary's most prominent and exciting sustainable and regenerative living sites. Details of the day are as follows...This excursion will be both educational and fun! Leave your vehicles or bicycles at our meeting place (The AREA 12:30 pm) and be escorted around Calgary for a tour of such notable places as Verge Permaculture, Patterson Springs Farm, The AREA and more. The tour will conclude in the evening with a locally brewed wine/mead and dinner at the AREA in Inglewood. More information can be found HERE!
Ted Bahr is the founder of Prairie Sage Permaculture