Bed PreParation: insurance for success 33
If you do not want to use chemicals, you can cover the bed area with several
layers of moistened newspaper and mulch or other light-blocking material such
as black plastic. (Some materials used as mulch include wood chips, bark, and
pine needles.) Then wait, perhaps up to 6 months depending on the conditions,
for the weeds to be destroyed.Well-draining soil
More perennials are killed by wet overwintering conditions than by actual cold
winter temperatures. This is why well-draining soil is essential for perennials.
Part of the research for my master’s degree focused on the cold hardiness of
herbaceous perennials. (“Herbaceous” refers to a nonwoody plant that dies back
to the ground every year.) Most of the species I studied were able to tolerate low
temperatures when everything else was constant, but these same species did not
survive in the field studies when exposed to excess moisture or fluctuating soil
temperatures. Perennials can simply rot during the winter if the soil is not
properly drained; this is often mistakenly attributed to cold temperatures, and
they are labeled “not hardy.” Yes, they are not hardy—to excessive moisture.
Perhaps you are one of the chosen few who have that perfect soil for perenni-
als—a fertile loam that is well draining but also retains adequate moisture. If so, I
am envious of you and wish you happy gardening! But most of us are not so
blessed. My own soil and most of the soil I work with for clients is very poorly
drained. Soil texture (the relative proportions of sand, silt, clay, and loam) can be
an indication of what kind of soil drainage you have. Sandy soils are sometimes
too well drained, requiring constant watering. On the other hand, if puddles tend
to stick around for more than half a day following a rain, or if your soil is
constantly soggy, you can be sure that you have a drainage problem (and proba-
bly lots of clay). Most of you probably know your soil type and are not happy with
it. (If you’re not sure of your soil type, you can run a percolation test, as described
below.) In any event, let’s discuss how to improve the drainage of your clay soil or
to increase the moisture retention of your sandy soil.
To ensure well-draining soil, avoid low-lying areas. Add organic matter to the
beds at the rate of approximately a third by volume, or 4 in. per 12 in. of soil—this
will also improve moisture and nutrient retention in sandy soils. (I will discuss
organic matter in greater depth later in the chapter, as it is so vital for all soils.)
Creating a slightly raised bed will increase the gravitational pull of water down
through the bed.a Simple percolation teSt
to check for proper drainage:- Dig a 12-in.-diameter hole the depth of the amended area.
- Fill with water and let drain.
- Fill with water again.
- Wait 1 hour. If the water hasn’t drained in less than 1 hour, drainage
needs to be improved either with further soil preparation or with tiles.
Drainage tiles may be needed in some cases to improve drainage, but this
should be considered only after you have considered all other factors. I have seen
isolated instances where the compaction of the subsoil during construction of the
home was so extensive that no matter what bed preparation was done, drainage
tiles were still necessary to improve drainage. Tiles can be expensive and will
often clog if not properly installed, so they are best used only as a last resort.