"Vacutone" wrote in message
s.com...
On Thu, 31 Jul 2008 19:43:03 +0100, Spider wrote
(in message ):

Hi,

I've read the exchange between you and Sacha. Sacha's idea of an avenue
or
concentration of hydrangeas is lovely - I've seen it done to great
effect.
You will undoubtedly want more! If you go down this route, it makes the
sub-terranean reservoir method of watering more worthwhile. To all
intents
and purposes, what you saw on the BBC gardening prog was a simple bog
garden
but with more drainage. Please don't mistake me and build a bog garden,
as
this would be too wet, but follow the general principles: a) dig out deep
depression b) line with strong plastic or butyl liner c) make holes to
allow *some* drainage d) backfill with soil e) plant your hydrangeas.
Having done this, if you subsequently think the area is too wet, simply
use
a garden fork to make more holes.

That makes sense.

I wonder if carving a basin into the clay subsoil would be useful. About a
foot down the soil turns into solid yellow clay, and a depression dug into
that will hold water indefinitely- well until it evaporates. Maybe I could
make a small reservoir there under the plant, something for it to dip its
roots into for a drink when its roots have grown that far, say maybe after
a
year, somethng like that.


I can fully appreciate what you're thinking, and it would be great for a
true bog garden. It may even work for a hydrangea in a very hot summer. My
concern is that, come winter, that yellow clay sump will hold more cold
(even icy) water than the hydrangea can cope with. Worse still, it may be
hard to alleviate once you've compacted that clay (which is how you get it
to hold water). Although it sounds counter-intuitive, you would be better
improving the clay, so that there is some post-"bog garden" drainage.
Without that extra drainage, the solid clay may hold so much water that it
begins to float the plastic sheet. If you want to be sure of sufficient
moisture, make your "bog garden" drainage holes in the sides of the liner,
rather than the base, so there is still *some* water after drainage. You
can, as I said before, increase drainage if you need to. Harder to reverse
that process, though, so take it gently. Once you've made this bed, you
won't be able to see what's going on below ground, so you need to build in
as much control over conditions as possible. Better to have a (reduced)
watering job in summer than a drowning hydrangea in winter.


And meanwhile the plastic sheet "bog garden" technology would help.

If you only want the one plant, you could add some water-retaining
gel/crystals to the planting hole and the soil you back-fill with. You
could also bury a length of pipe next to the plant to guide water to the
roots of the plant. This will encourage the roots to grow down, rather
than
stay near the soil surface where they may linger if you water normally.

Mulching is, of course, a great help - but not with a marble slab if you
want to encourage blue flowers.

Yes, I did wonder about that....

A seep hose (what Sacha was describing) is a good idea, too, but its
efficacy may suffer if the soil compacts, just as with normal watering.
One
solution to this may simply be gently forking over the soil periodically.

Spider

Ok- thanks!

--
Vacutone
Spider