Soils and potting mixes
J.E. Shields (Fri, 26 Jul 2002 16:20:29 PDT)

Hi all,

I doubt that we have decomposed granite available around here. Most of our
rocks are limestone, and about 100 - 200 ft straight down, below the soils,
subsoils, sand, gravel, and whatever. As you may guess, I'm no geologist!

Garden soils tend to be clays. If you are fortunate enough to have some
original topsoil left where you live, it is probably a sandy loam, loam, or
clay loam type. As former agricultural lands are converted to
subdivisions, the original topsoil may be sold off or may merely be buried
as the areas are graded for construction. Those poor folks in brand new
homes have their expensive sod laid on top of pure clay subsoil. When they
come to my garden for daylilies, I always advise them to hire a landscaper
with a backhoe to dig out the top 12 - 18 inches of clay and replace with
high quality blended topsoils, about $15 - $25 per cubic yard,
delivered. A few of them really do so. We can get a great triple-mix
topsoil here, composed of loam, local black peat, and sand (1 : 1 : 1).

In my pots, I use two basic mixes: One, my "sandy mix," is a Promix - sand
(2 : 1) mixture. The other one, my "gritty mix," is Promix - sand -
granite chick starter grit (ca. 2 : 1 : 1). These two do pretty well for
most of my plants. For starting small seeds and daylily seeds, I usually
use straight Promix, which is manufactured in Canada and is based on brown
Canadian peat mixed with a little perlite, vermiculite, and some rough
shredded twigs. You could probably use ordinary brown peat at 1/3 the cost
of something like Promix.

Pen Henry in the Clivia group suggested using a concrete mixer to make
these potting mixes up, and I finally follower her advice, thank god! It
works far better than mixing by hand. We bought an electric concrete mixer
at Lowe's, for about $250. It has never had cement in it and never
will. It has two wheels on one end, and I can roll it around. It is
stored in the garage, right beside the propane grill.

I grow my Hippeastrum, Cyrtanthus, Nerine, Haementhus, Clivia, and Crinum
bulbs in the the gritty mix. I start their seeds on the sandy mix. Both
mixes are indeed heavy in large containers. But since a large Clivia plant
in a 3-gallon container outdoors will be blown over in a typical summer
thunderstorm here, the more weight in the bottom, the better.

Because of the weight involved, I usually haul my potted bulbs around on
carts. Irma, my wife, found a neat 4-wheeled cart with a removable second
story in a garden supply catalog a couple years ago. It hitches to the
back of our riding mowers and is great for moving multiple big pots between
back door or greenhouse and the outdoors areas in spring and autumn.

In summer here in central Indiana, we can have anything from very wet to
very dry weather, anything from mild to hot temperatures, and almost always
high relative humidity. It can be tough to get clivias through a wet,
rainy summer outdoors. Some of my Haemanthus are not very happy in the
humidity too. Almost all my Haemanthus carneus are on strike this summer;
it looks like they would rather rot than grow. H. humilis hirsutus and H.
montanus, however, are apparently doing pretty well. If I ever get the
montanus to bloom, I will certainly cross it with hirsutus to pursue my
quest for another Haemanthus besides albiflos that it is humanly possible
to grow here.

Regards,
Jim Shields
in central Indiana, where it is a mite warm and humid after a quick mid-day
thunderstorm.

*************************************************
Jim Shields USDA Zone 5 Shields Gardens, Ltd.
P.O. Box 92 WWW: http://www.shieldsgardens.com/
Westfield, Indiana 46074, USA Tel. +1-317-896-3925