Re: shade/bog gardening
Well, Melody, if lilacs are growing in this area, it means it
actually has decent drainage as they are not plants that will
tolerate wet feet for very long.
It appears that the major problem is that the water is going on down
to his neighbor's yard...
My experience with water in really heavy downpours is that once it
fills up an area, it will overflow that area and continue on down
hill. This is what happens to my 'bog' garden - really a damp garden
- that is built over the 6" PVC flexible pipe that picks up water
from several downspouts. Once enough water has fallen to fill all
available air space in the garden, water collects on the surface of
the garden - basically in the lower spots there - and then, when that
fills up past the lowest point of the edge, it drains out and flows
down the path around the garden and on down my hill to a drainage
swale that eventually ends up in a creek about 100 feet on down hill.
So, while creating an artificial 'bog' at the end of a drain pipe is
perfectly possible and in normal rains will absorb most all of the
water without overspill AND will keep the soil in that garden damp
all year around, it will NOT handle all the water from a really heavy
and/or sustained downpour. This means that water under those circs
will still travel into the neighbor's garden.
If a section of the neighbor's garden floods during heavy rains, that
means to me that the grades in that garden are not allowing water to
drain away easily - there has to be some depression there that holds
water until it reaches the top before it can drain out and finds a
way further downhill. Unless the drainage in the neighbor's garden
is corrected, this will always happen in a gully washer, particularly
if your friend is collecting water from his property in one spot
adjoining a lower grade at the neighbor's property...water always
goes downhill and will find the easiest way to do this.
Your friend can build a dry well to collect water from his
downspouts. This may be more effective in preventing flooding of his
neighbor's yard but, again, in a major, sustained heavy rain, it, too
The difference is that a drywell is filled with stones to aid in the
water draining out where a bog garden is lined in plastic to keep it
If you decide to build a bog garden, you do not need a block wall;
just dig a depression about 15" deep and line it with plastic. Mine
took 2 sheets; I just overlapped the joint. Water will find its way
out at the joint, but that's OK, enough is kept in to keep the soil
moist and you do want some drainage so it doesn't get stagnant. You
then need something to conceal the plastic at the edge; I used logs
as I had a major quantity of them, but rocks or flagstone would do
the trick. If you use plain old PVC plastic sheet (6 mil at least)
you have to make sure it is not exposed to sunlight as it degrades
quickly; breaks up in little bits. If it's totally covered in soil
it will last a long time.
The only harm building a bog would do the lilacs would be damage to
their roots when digging the hole.
Depending on the amount of light / sun reaching the location, there
are hundreds of plants that love continually moist to wet
soil....candelabra primroses, carex, astilbes, rushes, Japanese iris,
Siberian iris, Chelone, Veratrum, Lobelia are a few in my 'damp'
As much as I love my damp garden and wish it were larger, it is not
exactly a low maintenance item, so if your friend is trying to move
that garden into low maintenance, seems to me he should concentrate
on the dry well and stopping as much flooding of his neighbor's
garden as possible and not in creating a new type of garden to
If his roof drain is running across the garden, maybe it passes a
spot where not much is growing and a dry well could be dug without a
lot of problems - or this could happen fairly close to the house; far
enough away so water doesn't go toward the foundation, tho' - then
the pipe would terminate at that point instead of where it now does.
This also means that any overflow would be absorbed more by his
property before it hit his neighbor's property.
Hard to tell what size dry well would be needed without seeing the
situation, but I'd imagine it would need to be at least 3' in
diameter and about that deep to contain a lot of water. This would
be filled with stones of varying size from gravel to larger and the
pipe terminated there. The top needs some kind of silt cloth to stop
it silting up fast and that could be topped with smaller gravel and
planted or a grate put on it; depends on what and where, etc. I also
used perforated drain pipe so that some of the water would leak out
on the way down hill - just waters more land while containing the
When you concentrate water flow, you always get a larger amount at
the spill end than if it simply travels over land naturally.
Being on the side of a hill, drainage and where water goes and what
it does while it's doing that are a continual education and challenge
for me. Last year, with the really heavy rains we had, rain came
down our drive so fast that it dug a trench about a foot deep in the
driveway gravel (3/4" bluestone that's been compacted there 14 years)
and pushed the gravel it dug out down into a border from which I have
still to excavate all of it. And this despite the fact that I'd
already dug a foot deep trench along the edge of the drive to direct
the flow during heavy rain; the water ignored that one and made
another to suit itself! My trench works fine during normal rains.
It took half of my pea gravel walk - down to and including the stone
dust under it and some of the larger rocks I'd put under that! - down
the hill...gotta solve that little problem one of these days; gettin'
tired of hauling that stuff back up hill.
You really need to simply observe what water is doing during heavy
downpours a while to figure out what you need to do to divert it or
otherwise mitigate the force.
Marge Talt, zone 7 Maryland
Editor: Gardening in Shade
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> From: Melody <email@example.com>
> Dear all: I need help for a friend's yard...It is his mother's
> which now that she has retired and moved south, he has
> "inherited"...with one giant problem...Mom was a huge gardener and
> not. So now he is faced with the upkeep of an extensive shade
> collection that he neither knows nor really cares about, but to
> mom happy when she visits every so often, he would like to do
> with it while simplifying the work. She was really into hostas in a
> way and they are everywhere. Also tons and tons of lily of the
> that are spreading like wildfire, even where he doesn't want them
> (Kitty...who knew? Sorry!) So, I've agreed to help him revamp all
> those things, but our biggest problem proves to be one of
> has an area in his yard to which he runs a drainage pipe for
> from his roof that in heavy rains, runs across his yard and floods
> neighbors yard in the corner where the two meet...It's a heavily
> area that contains mostly a beautiful collection of lilac trees, a
> hosta and lily of the valley...would the creation of a boggy area
> with cinder block and plastic liner a) be enough to contain the
> it doesn't flood the neighbors and b) be damaging to the lilacs in
> way? Also, what would one put in a boggy area like that?
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