Sunday, May 26, 2013

Forest Garden Windbreak, Part 2

This just-planted myrobalan ruby® is already facing up to the wind

In my previous post, I talked about our need to create a microclimate that is favourable to the trees, shrubs and plants that we want to grow in our forest garden, helping them to develop and fruit better. The aspect of climate that we are dealing with here is obviously wind.

Despite the range of plants offered in our two reference books, Patrick Whitefield’s How to Make a Forest Garden and Martin Crawford’s Creating a Forest Garden, we felt that we wanted even more choice. We are beginners in forest gardening and don’t yet have an encyclopaedic knowledge of plants, so we needed a strategy. One principle of permaculture is that each element should perform more than one function, so we decided that the trees and shrubs in our windbreak should do something more than just cut the speed of the wind. Our criteria were that each tree or shrub should either provide something edible for us, food for bees or fix nitrogen for other plants, and we always like to remember the aesthetic too; why not be beautiful as well as worthwhile.

We searched on the Internet for nurseries that listed plants to be used in windbreaks. We’re English, so although we live in France and speak reasonable French, it’s still easier to conduct this sort of research in English. We found these sites useful:

We copied and pasted the plant lists from these websites to add to a list of plants suggested by Whitefield’s and Crawford’s books. To verify that the plants were suitable candidates for our permaculture windbreak we checked each plant in RHS A-Z Encyclopedia of Garden Plants to see if it was hardy and not susceptible to winds. If it passed that stage, we considered how it could be useful. We had a reasonable idea of what was edible and the types of plants that fix nitrogen and we used another of Crawford’s Agroforestry Research trust publications, Bee Plants which is a directory giving details of over 1050 species which are of use to bees, both solitary and honey.

Another aspect to consider is how early a windbreak plant comes into leaf, offering more than twigs to protect delicate fruit blossom from cold spring winds and how long they hold onto their leaves to protect ripening fruit from autumn winds.

To be honest, we could probably have made do with the lists provided by Whitefield and especially Crawford but following this process of searching around reference books and the Internet has helped us to increase our knowledge of plants and their characteristics.

We’ve planted just over thirty trees and the same number of shrubs this winter. We started with the north edge, which needs to be taller. Running out of time and money, we’ll complete the task this winter coming. We planted little plants, which are not only cheaper but will establish better anyway. This is our list but don’t take it as definitive. Permaculture is site and situation specific, so you’re better off following a similar sort of process to choose suitable plants for your windbreak.

After the windbreak comes the tree layer, this latest blog by Patrick Whitefield tells you how to go about it.
holm or holly oak  (Quercus ilex)                                                  
grey alder (Alnus incana)                                                              
sitka alder                                                                                   
willow (daphnoides )                                                           
cherry plum, Prunus cerasifera                                                           
silver Birch Betula pendula                                                           
Dwarf mountain pine Pinus mugo

Elaeagnus × ebbingei                                                           
autumn olive, Elaeagnus umbellata                                                  
sea buckthorn, Hippophae rhamnoides                                    
Ramanas rose, Rosa rugosa                                                           
pyracantha “Mohave”                                                             
New Zealand flax, Phormium tenax                                                
daisy bush, Olearia cheesmanii                                               
daisy bush, Olearia macrodonta                                               
strawberry tree Arbutus unedo                                               
barberries: Berberis darwinii                                                
butterfly bush, Buddleja davidii                                               
escallonia rubra ‘Crimson Spire’                                                
blue honeysuckle, honeyberry, Lonicera caerulea                                    
Chinese bramble, Rubus tricolor

Tuesday, May 14, 2013

Forest Garden Windbreak, Part 1

Thanks to the Cowlitz County Sheriff's Office Department of Emergency Management for this visual metaphor
Yet another one to be filed in the cluttered “we learn from our mistakes” tray. We observed, we measured, we surveyed and we drew a lovely plan with coloured circles representing the mature canopies of just the right amount of fruit, nut and nitrogen-fixing trees. We thought that the first thing to plant in a forest garden was the tree layer, especially when one considers how long it takes trees to grow and to grow to an age when they’ll start fruiting. We now realise that the first thing to plant in a forest garden is the windbreak.

A little snowbell tree, Halesia carolina, never made it through its first winter and it was only after its demise that I turned to The RHS A-Z Encyclopaedia of Garden Plants and found that, although it’s hardy, it should be sheltered from cold winds. The field being planted up is exposed to the north (cold, dry winds) and the west (winds from the south west and west, often wet).

Oft-repeated permaculture wisdom is to observe for a year, seeing your land through four seasons before making planning decisions. It seems strange but it’s only this winter that I’ve become aware of just how exposed this site is and just how windy it gets. Perhaps it’s that we sometimes only see what we want to see and are otherwise oblivious to something staring—maybe that should be blowing—us in the face. I notice it now. In fact, I automatically note what’s happening wind-wise each time I visit the field … and it’s often impressive. So, we need some sort of windbreak.

Our two reference books are Patrick Whitefield’s How to Make a Forest Garden and Martin Crawford’s Creating a Forest Garden, both are useful but the latter has more specific detail on windbreaks.

Martin talks about a “quiet zone of protection” just behind the windbreak, followed by a turbulent area. There is a calculation: the quiet zone “extends for seven or eight times the height of the windbreak.” Our forest garden is 33 metres wide (E/W) and 50m tall (N/S). That suggests our northern windbreak should be 6½m tall and the western edge 4½m tall. We’ll use that as a guide but taper the western windbreak towards the southern end so we don’t shade out the afternoon sun or affect the wonderful view too much.

Martin also suggests planting trees and shrubs that grow to the size required and therefore don’t require onward maintenance. Nice idea, but we think that particularly difficult to manage as trees will grow to different heights dependant on their soil and situation, in our case being closely planted with other shrubs and trees. We decided on a line of trees with a line of bushy shrubs in front, 1.2m between plants and 1m between the lines, the second line offset from the first by half, so that the shrubs block up the holes at the base of the trees.

We thought the list of plants suggested by both books were a bit limited, so in the next blog, I’ll explain how we chose our plants and what they are.