52 Basic Perennial Garden PlantinG & Maintenance
watering. In my own gardens, although I will coddle newly planted perennials,
watering well until established, I irrigate established plants only when I think
they can’t possibly stand another dry day. This is sometimes after weeks with
minimal rainfall. Sure, some plants will succumb to drought, but most tolerate
these conditions. There is no need to waste a valuable resource such as water,
particularly when large quantities of water are not necessary for a beautiful
perennial garden. Don’t try to keep a moisture hog, such as ligularia, alive in an
extremely dry site at the expense of excess watering. I have been able to grow
ligularia in soil that remains moderately moist by lining the planting hole with a
plastic bag to create a bathtub effect, which holds more moisture around the
plant and reduces the need for large amounts of supplemental watering. The
plants still usually wilt midday on hot days, but they recover nicely by evening.
A garden, particularly a new garden, should be watered into autumn as long
as it is dry but not frozen. Just as perennials need well-draining soil for proper
overwintering, they have a better chance of survival if they don’t go into the
winter in a dry condition.
If you are using an automatic irrigation system, make certain that the timer is
set for more frequent, shallower waterings when the plants are establishing. As
the plants establish, adjust for deeper, less frequent waterings. This is often a
problem with automatic systems, as contractors set the timers as they do for turf,
which is not appropriate for perennials. Drip irrigation systems have the great
advantage that they are more efficient at moisture conservation, but the disad-
vantage is that problems in the irrigation system can go undetected because you
can’t see them. Watch plants with subirrigation closely for signs of line failure,
be it a leak or clog. Make sure that the irrigation system has a rain gauge so that if
sufficient rain has fallen, your irrigation will shut off. Troubles with irrigation
can be a big problem with perennial plantings during establishment and in
subsequent years if not closely monitored. Whatever irrigation system you
choose, if you are not setting it up yourself it is a good idea to meet with the
irrigation contractor to review the garden design, with its varied cross section,
before the system is designed and installed. If using above-ground systems, make
certain that taller plants are not blocking the spray from adjacent shorter plants.FERTILIZING
Most perennials do not require large amounts of fertilizing; some, in fact, may
resent such treatment, responding by producing excessive vegetative or leggy
rank growth, minimal or no flowers, and possibly stunted root systems due to the
highly soluble salts in the fertilizer. Silver-foliaged plants are particularly
sensitive to overly rich conditions.
If soil is prepared properly from the start with nutrient-providing organic
matter, supplemental fertilizing or topdressing might not be necessary for
several years after planting. Studies have shown that a soil amended at bed
preparation with 20 percent well-aged, quality compost, with an analysis of 1
percent nitrogen, will be sufficient to support most annual, perennial, tree, and
shrub growth for at least the first year without any additional fertilizer. Nitrogen
availability from such a compost usually is 25 percent for the 1st year, 10 percent
for the 2nd and 3rd years, and declining to 5 percent in the 4th and 5th years. This
means that if 1 in. of compost is used at bed preparation, 4 lb. of nitrogen per
1000 sq. ft. will be available in the 1st year. This is remarkable because the
general recommendation for perennials is 1 lb. of nitrogen per 1000 sq. ft.
However, organic nitrogen is dependent upon warm temperatures and microbial
activity for release; in cool conditions, a small amount of quick-release fertilizer
at planting will ensure adequate nutrients until the nitrogen is released in the
compost with the coming of warm temperatures.These plants are thriving
in a soil amended with nutrient-
providing compost that drains
well.