sustag at eircom.net
Wed Jan 4 20:50:36 EST 2012
I'm in Ireland, like John, and have problems with drainage, given the high
amounts of rainfall. I have planted a lot of willow and many other tree species,
for all sorts of reasons, including wind shelter, fodder, firewood, bee food
etc. and also drainage.
It is important to remember that trees not only evapotranspirate (and they do a
little of that also during dormancy as they keep up their life functions) but
their deep roots also change the soils' basic physical and hydraulic properties:
they reduce soil water retention, increase hydraulic conductivity, and loosen
the soil structure, in comparison to grassland cover.
I think what Steve may have meant when he said to keep them at a constant growth
stage by coppicing is to keep them at their maximum annual growth rate. A tree's
growth rate is higher when they are younger and levels off as they mature.
However, for the purpose of maximum evapotranspiration it may be more beneficial
to have a large tree with a lot of leaf surface rather than a small and fast
growing one? I don't know.
re willow species: I have planted dozens of different willow
species/hybrids/cultivars on our land and I have found that here, in the West of
Ireland, the one which puts out leaves the earliest (c. late January) and holds
on to them for the longest time (into November/December) is Salix sachalinensis
'Sekka' (Japanese Dragon willow). It also grows very quickly and produces large
amounts of biomass. Due to the very long growing period it should be a prime
candidate for drawing water. Unfortunately it does not strike easily from
cuttings like most other Salix sp.. It has to strike roots in water and then
needs to be planted out (rather than just cutting a branch and sticking it into
the ground). Let me know if you want cuttings John or anyone else in Ireland.
I'd be happy to cut and post some cuttings for the cost of postage.
Eight years ago I planted a 200 m hedge along a drain on a field on fen peat
soil. The drain borders my neighbour's land, sloping down from a drumlin. Our
field is on level ground. As the drain is no longer accessible by machinery from
either side I decided to go for 'pumping' species rather than having to manually
clear the drain. The trees also shade out the
drain, preventing grass growth from clogging it up. Did a bit of research and
came up with the following list for our situation (also wanted something I could
lopp for our goats). All these are suited for wet sites and are considered
Alnus glutinosa (Common alder)
Alnus incana (Grey alder)
Fraxinus excelsior (Ash)
Prunus padus (Bird cherry)
Rhamnus frangula (alder buckthorn)
Salix sp. (willows)
Sambucus nigra (Black elderberry)
Sorbaria sorbifolia (False Spiraea)
Viburnum opulus (Guelder Rose)
I planted a mix of these and they are doing well. Between taking up a lot of
water during the growing season, improving drainage, and keeping the existing
drain clear the field has definitely improved (also aided by a three-row mixed
tree & shrub hedge on the other side of the field). It used to have water lying
right at the surface for long periods. Now that's a transient phenomenon for
brief periods after heavy winter rains only.
Sorbaria is quite slow-growing here but it finally seems to kick in now (7-8
years on). Alnus glutinosa is fantastic, very fast growing. It can also be
coppiced for firewood. Sambucus is great of course for its berries. One of my
favourite willows for this situation is one I got from westwaleswillows.co.uk
(great supplier and great info on their webpage by the way): Salix nigricans. It
creates nice dense bushy growth, great habitat. I also threw some Elaeagnus into
the mix as I found they do well on that type of ground.
Other 'pumping' species for wet ground that I came across but did
not plant include:
Populus alba 'Nivea'
Populus canadensis 'Robusta'
Populus nigra 'Italica'
Ulmus carpinifolia 'Wredei'
Ulmus hollandica 'Lobel'
Of course there will be more/others for other climates and other continents.
This is a list for NW-Europe.
Hope this helps all those who don't struggle to keep water *on* their land but
rather to get rid of it ;-)
Wednesday, January 4, 2012, 7:07:52 PM, you wrote:
JDh> Only that willows don't do leaves here in winter when you would need them
JDh> most. They do help while growing.
>> G'day, I wonder how big an effect willows will have on lowering the water
>> table and whether your land supports many trees that can evapotransirate
>> water out of the ground. Keeping these water loving trees in a constant
>> growth cycle by coppicing may help with drainage over the growing period
>> and the leaf drop will add to SOM.
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