Eucomis - TOW-Hardiness

Boyce Tankersley
Mon, 18 Aug 2003 09:36:24 PDT
Hi Dave:

Great information on those taxa most likely to be hardy. I forwarded it onto the horticulturist in charge of the Bulb Garden. 

She and I have been discussing hardy bulbs that we can use in Bulb Garden displays that can be used in association with the fall bloomers like Colchicum, Lycoris, the fall blooming Crocus, etc. Our gardens feature intensive displays. Currently annuals are used to 'carry' the flowering season throughout the summer for these groups of bulbs. It is not the best solution. Many fall flowering bulbs damaged in the process of overplanting with annuals. Eucomis, given the summer growth and flowering and (hopefully) hardiness would be a much better solution than annuals. Newer Crocosmia cultivars are very showy and have been tried but apparently are not reliably hardy (perhaps the chipmunks favor the corms - I know the deer and rabbits apparently relished the foliage or maybe it is a simply lack of cold temperature hardiness).

With regards to microclimates, we're finding placing plants, including bulbs, in areas that are shaded in early sunrise is our best approach to those that have a tendency to start growth too early. The theory that we have adopted to explain the results in our Garden goes something like this "Apparently the localized warming of the plant tissues in direct sunlight while still surrounded by frost inducing temperatures results in plant tissue injury (locally known as frost cracks in many woody taxa). One theory is the rate at which ice crystals in the plant cells dissolve is important. Those taxa prone to starting growth too early in the season show less tissue damage if sited in a location that is shaded from the first sunlight of the day. This situation (shady and therefor cooler) may discourage them from early season growth as well.

We continue to observe and modify the theories. Part of the fun of this profession.

Boyce Tankersley

-----Original Message-----
From: David Fenwick []
Sent: Monday, August 18, 2003 10:35 AM
To: Pacific Bulb Society
Subject: Re: [pbs] Eucomis - TOW-Hardiness

In the wild Sentinel Peak regularly gets -10C each year.
Thus species such as E. schijffii, E. autumnalis ssp. clavata and E. bicolor
should be OK. However, I should imagine that those grown from seed collected
from such areas may be a little hardier than those collected from lower
altitudes. I have them hear in the heaviest soil on the garden, a clay loam,
buried 6 - 7 inches deep, and they come back annually, with temps down
to -5C with no problem and no mulch.

Here I plant bulbs just deeper than the worst frost can penetrate, and this
seems to work here. Thus if the frosts penetrate to 12 inches in Chicago,
try planting them 13 inches deep. I think it would be wise to plant mature
bulbs this depth though. Remember the deeper you go in the soil, the more
stable the temperature, and thus freak warm winter temps. shouldn't break

One other tip is to go out into the garden early in the morning after a
heavy frost. Watch the sun come up, and note where the frost melts first.
Thus by planting in these areas, which will get less frost, you'll find a
little microclimate for them.

Best Wishes,


David Fenwick
NCCPG National Collection of Crocosmia with Chasmanthe and Tulbaghia
The African Garden
96 Wasdale Gardens

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