40 Basic Perennial Garden PlantinG & Maintenance
BED PREPARATION TECHNIQUES
Once you determine your soil type and what materials need to be added, it is time
to prepare the bed for planting. As stated earlier, adding 4 in. of organic matter
per 12 in. depth of soil is ideal. It is important to work the organic matter into the
beds as deeply as is practically possible. The plants will root more deeply, thus
improving their tolerance to drought, cold, and fluctuating temperatures.
Organic matter also breaks down more slowly when incorporated into the soil, so
the benefits are longer lasting than if it were just spread on top of the soil. Tilling
will bring weed seeds to the surface, so you must be vigilant about weeding the
bed during its establishment. Planting densely, mulching, and providing
perennials with enough water and nutrients so that they will fill in quickly will
ease the weeding burden.
Double digging is sometimes recommended for preparing a new perennial
bed. If you haven’t heard of this backbreaking technique, count your blessings. It
involves removing 12 in. of soil, amending the subsoil with organic matter to an
additional depth of 6 in., amending the removed topsoil, and then returning the
amended topsoil to the bed. Double digging is said to be wonderful for the soil;
I’m not so sure of the consequences to the digger. In fact, I’ve never noticed any
differences in plants’ performance when they are grown in double-dug beds as
compared to those grown in rototilled beds.
I usually don’t go the ideal 12 in. deep when preparing beds. I am able to work
down 8–9 in. with a rototiller, which for practical purposes is what I do with my
business. Only in the rare cases where we are renovating a perennial bed, and the
beds had been worked and amended in previous years by the client, have we been
able to till 12 in. deep. I have had great success with tilling to shallower depths
and still adding 4 in. of organic amendments, which also serves to provide
slightly raised beds. Going only 8 or 9 in. deep means organic matter is being
added at approximately 50 percent by volume.
Adding the soil amendments is the most labor-intensive part of installation.
First we till the existing soil, then we start adding our different amendments one
at a time, re-tilling and blending these in with the existing soil. We make several
runs over the beds, working to greater depths and blending each time until it is
workable and ready for planting. The amendments are raked and leveled on the
beds, with a final leveling with rakes when all the tilling is done. By the time the
whole process is complete, it’s like planting in chocolate pudding—truly a treat.
Wheelbarrows are usually sufficient for transporting the soil amendments to
the beds. Construction equipment (such as a Bobcat tiller attachment) is
required only with very large amounts of organic amendments or when there are
long distances to travel. Heavy equipment can create compaction in the garden.
Care must be taken not to create a cleavage point where the good soil meets
the poor existing subsoil, or a hardpan (a hardened or cemented soil layer) can
develop. I generally do not experience this problem, but in cases where the tiller
can’t penetrate the existing soil, sometimes the subsoil must first be worked up
by hand, using shovels and forks. Then you can get through it with the tillers. I
have heard of cases where companies come in with a back hoe to loosen the
existing compacted subsoil, then the soil is worked in by hand and with tillers to
incorporate soil amendments and ensure organic matter to a greater depth in the
soil. Sometimes the existing soil is removed completely from the site and new
soil and organic matter is brought in. Very seldom do I have to do this, even in
our poor clay soils. If this method is used, it is still important to make sure there
is not a point at which the new soil meets with a hard layer of poor compacted
subsoil.
The soil should be dry before you try to work it, but not too dry, as tilling soil
when it is either too wet or too dry can damage the soil structure. Scheduling