More fall crocuses

Jane McGary
Sun, 09 Nov 2003 17:57:01 PST
Rodger Whitlock's question about my potting mix is difficult to answer in 
the detail he asks for, but I will try.

>Tell us all a little more about your coarse, sharp upriver sand. What
>kind of minerals are in it? Which river? (Some of us *do* travel
>through Oregon, you know.)

It comes from a quarry fairly high up on the Clackamas River, which drains 
the Oregon Cascade Mountains just south of Mount Hood. It contains basalt, 
quartz, and perhaps some other minerals. I've found petrified wood in it 
occasionally. I haven't had it analyzed. It is sold as concrete sand but a 
concrete contractor I talked with told me it was lousy for that purpose, 
being too coarse and "dirty" -- the qualities that help make it perfect for 
plants. You are welcome to show up at my place with a couple of garbage 
cans, Rodger; there's a big pile of it here at all times.

>And the pumice: what screen mesh would you use for this? We can
>get bags of a whitish horticultural pumice here (probably imported
>from Oregon in bulk and repackaged), but I'd be interested to know
>how coarse or fine the stuff is that you use.

That stuff in the bags is exactly what I use. I buy it in bags (about 50 or 
60 pounds) because it's easier than shoveling it and having it lie around 
getting weed seeds in it, and I can carry it in my little car instead of 
taking the truck to the city. I think it is 1/4 inch minus. I have been 
told that this product has a fairly high pH, near 7, so it would counteract 
some of the acidity of the sand and humus. I sometimes add a little 
slow-release lime to the mix, but not always.

>And as for the forest humus: what species contribute to it?

Alder (Alnus rubra), vine maple (Acer circinatum), thimbleberry (Rubus 
parviflorus), trailing blackberry (Rubus sp.), and a little Douglas fir 
(Pseudotsuga menziesii), and herbs such as Dicentra formosa and Montia. In 
other words, the same plants Rodger probably has in his woods if there is 
some surface moisture. Alders are nitrogen-fixers, so the soil under them 
is quite rich. I put it through a coarse sieve to get the large chunks, 
bugs, etc., out, but it is not sterilized. In fact, it is probably loaded 
with nematodes, fungi, and bacteria -- yet it seems to be better for the 
bulbs than any other organic component I've used. I prefer to get soil from 
the woods rather than the fields because the weed seeds are less of a problem.

There was apparently a question that I missed either here or on Alpine-L 
about sieves. Rex Murfitt was explaining how to make one. If you are not as 
handy as Rex (I definitely am not!), you can get excellent, indestructible 
plastic and wire sieves in all sizes from mining supply stores, which are 
also on the Internet.

I don't think my soil mix has much to do with whatever success I achieve, 
although it does provide a lot of air space and rapid drainage, which is 
important for some bulbs. Probably regular repotting in fresh soil, 
application of fertilizer, good air circulation, and managing moisture are 
more important than what the bulbs are growing in. After all, in nature 
many of these bulbs grow in heavy clay (e.g., Fritillaria pluriflora, many 
Calochortus) or soils derived from limestone (many of the crocuses we've 
been illustrating) or even ultramafic rock (serpentine).

Jane McGary
Northwestern Oregon

More information about the pbs mailing list