Have you just planted seedlings and saplings of what hopefully will become a
large grove of new trees?
If so, often the climate you have will make it difficult to establish the
trees. You may have introduced new, non-native trees, which once established
will thrive and be a boon to the ecosystem. You may have used severely
compacted soil, since in urban settings the earth has often been
criss-crossed with heavy construction machinery. You may have used imported
soil, which at its worst extreme, could be mostly just sand and boulders.
Other challenges novel to the urban forest include animals, including all
insects as well as humans, that may eat or otherwise vandalize the trees.
When you plant a new grove of urban trees, getting them water is one of the
biggest challenges of all. Artificial structures, streets, buildings,
parking lots, redirect runoff and prevent natural sources of surface water,
so even if you're planting native trees, they may need water. Often the
water table is altered in urban environments and should be taken into
account. Supplemental summer waterings often spell the difference between
bare survival and awesome growth rates. Redwood trees, for example, if
properly watered, can grow up to ten feet per year, even outside their
range, even in the city.
Over the last few years www.EcoWorld.org in
collaboration with urban reforesting organizations as well as private
property owners has helped to plant dozens of groves of trees, mostly large
native trees in Northern California. This has given us experience with various types of urban
systems, from a three acre grove of Redwoods on the hillsides of a former
dairy farm near Glen Ellen (40 miles NNE of SF), to a grove of Evergreen Ash
in the islands of a similar sized (three acres or so) parking lot in West
San Jose (40 miles SSE of SF).
Our experience shows that one of the most cost-effective and time-effective
ways to deploy a durable system that will ensure excellent results is to use
rolls of 1/2" diameter flexible plastic pipe. Rolls with 500 feet of pipe
can be had for about $30, and with adequate water pressure a pipeline like
this can deliver water to trees many hundreds of feet away These prices are circa 2000 and in any event for larger systems or where squirrels may try to gnaw on the pipe, you will need heavy-duty thicker 1/2" pipe, which is more expensive. The
installation instructions provided here use a relatively small system as an
example, but the system can be scaled to run for hundreds of feet to supply
hundreds of trees.
If you are unfamiliar with these systems, you should read the materials list
before reading the instructions. Also note that these instructions are for
a basic manual system that will need to be manually turned on and off during
the dry season. Still, a system like this can eliminate the need for hand
watering each tree, and because of the low flow drippers, can actually
deliver better deep watering. For a few hours work and about $50 you can
reduce the time you'll need to spend watering your grove to a few minutes
each week.
