OK, I've got some water in place though at 1000 litres it'll need topping up (by Michel) during the season. Some lessons learned from the very first season's watering. A good concept (reasonable tree growth and also some fruit) that needs much more work. The homemade watering collars need to drip, not flow. Putting nutrient in the tank is a bad idea. Light, warmth, water and nutrients leave the tank full of green scum at the end of season. Karchering that lot out wasn't fun. So for 2011 the plot was brown dripper hose collars around the trees. Osmocote around the trees and clean water in the tank. Camouflage netting over the tank to reduce the light. That's why they sell black tanks but you'd then have to paint it white. The 2011 result was quite encouraging. Reasonable crop of Concorde pears, Spartan equivalent apples and the Victoria plums had been eaten by the time we got there. However the very low pressure means that there is only so many trees that one can irrigate at a time. So the current plot for the 2012 season involves two Gardena timers, each with a sensor and doing half the trees each. The current tree count is, at various levels of maturity. One good and one not so good Victoria. Bird cherry, Stella cherry, rose and yellow cherry and a white cherry (theory is that the birds can't see it. Two apples. Nectarine. Vine peach. Agen plum. Concorde and William pears. Greengage. Fig. Mulberry.

Construction

1000 litre cubes are fairly common around here, for harvesting rainwater. So I built (actually there was a lot done by my neighbours Henriette and Michel and very good they were too) a concrete block work cube about 1.5m high and large enough to take the cube (1.2m by 1.4m). There was a decent foundation (there’s a tonne of water here). Then leave it to cure for a month or so.

Water distribution

Forget soaker hose, not enough pressure. So I landed up making collars (one per tree) of 12mm polypropylene garden hose, each being a ring with a single feeder point. The idea being that the size of the collar (about 1m) and the spacing between the 6 holes would about be capillary distance. Then tune the size of the holes in each collar such that they were even (about 1.5mm).
The thing that did surprise me was friction. It’s very evident at low pressure so, in order to give each collar about the same flow, all the tubes to the trees are going to be the same length. A nuisance but there we are.

What might work?

I couldn’t find anything in one place on the net that addressed the requirement, hence in part, this diary. Research over various areas yielded the following points:
• Fruit trees like to be slightly parched and then drenched
• Water them first thing in the morning
• The only metric I could find on volume was for each one inch of thickness give 5 (American) gallons per week, so 20 litres per tree per week.
• I will have to provide my own water pressure.
• One bar is 10m head of pressure
• 1000 litre cubes are common here but that’s a tonne of water
• No way am I building a 10m tower, maybe 1.5m is possible
• 0.15 bar is very low pressure.

Low pressure is a real issue. Forget soaker hose, it needs 2 to 3 bar. Forget most automatic timers; they need pressure to close the valve. So what I landed up with was:
• A Gardena programmer, works on no pressure, batteries will run for the season. The user interface is clunky but it provides adequate facilities to open the valve at a time, for a period, every whatever.
• An associated Gardena soil moisture meter. Bury it close to one of the trees and it’ll tell the programmer if it’s wet or dry when the programmer is debating whether to open the valve. How cool is that?

The requirement emerges

Over the years I had imported various fruit trees. A Victoria plum, simply because I think they’re the finest plum there is (although, apparently, not quite as hardy as I imagined initally). Another Victoria because the first clearly wasn’t happy. A Concorde pear because I think they’re great as well. An Abat Fretel, a local pear. A mulberry and a couple of cherries.
This should all have worked but owning another house in a different climate is always a learning experience. The approach to laying patios is different, so also are plumbing joints, both because of the -15C we often experience in winter. Blue sky and very little snow but it can get very cold and stay that way. The local record is, I think, -29C sometime in the late 70s.
Termites are new to Brit arrivals and there is no Silverleaf (but there is Colorado beetle) so the plums can be pruned anytime after flowering.
Gradually as I began to understand this type of issue better it dawned on me that the orchard simply was not viable without quite a lot of help. Yes, it does get lots of sun. But the water in the Dordogne generally is pretty hard and the terrain is frequently a not very friendly combination of chalk and clay. And the rainfall between Easter and October can be pretty light. And when I tested the soil it was pretty much nutrient free.
So quite alkaline soil (sort of 8.5ph and pears hate it), no nutrients and no water.

Background to the project

We bought our house in the Northern Dordogne in 1998. The day that we signed we discovered that we had an additional parcel of land, opposite the house but on the other side of the chemin that runs beside it. At the time it seemed like an ideal site for an orchard, not large but not small either, about 500 or 600m2.
Time moved on (about 10 years in fact) and the house and garden got sorted out. I did install two apricot trees in the front courtyard, well shielded from the north wind and getting afternoon sun. They do now produce rather good apricots in early July and one year, we promise ourselves, we'll be down to eat them from the tree. Meanwhile various neighbours really do appreciate them and eat most of them. And preserve some for us so that's OK.
Meanwhile nothing much had happened in the orchard. A reine claude and two apples went in, struggled but eventually survived. Ditto a fig (they grow like weeds locally, dark blue skin, red flesh and delicious ripe from the tree) planted in a frost pocket but, when it did manage to survive our pretty cruel winters, is also in full sun and productive.