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Isodon excisus

Isodon excisus
Isodon excisus
Isodon excisus

Family lamiaceae
Life cycle perennial
Flowers blue
From seed germinate at room temperature, do not exclude light
detailed seed-starting info below
Seed ripensearly October

I received seed for this plant in trade from James in Ohio. He writes about it:

the genus Isodon, like many genera in the Lamiaceae, is virtually unknown in cultivation. I call them hardy spurflowers, due to their close relation to the tender spurflowers (Plectranthus). This species, which comes from western Asia (Japan, China, Korea, etc) forms a woody stump from which many typical square stems arise; the wrinkly leaves have an excised tip (hence the name). The flowers are born in dense sprays and are brilliant indigo in color with darker purple spots on the lip; they are also upside down (the lip is on the top) a feature unique to the Ocimeae (basil) tribe of the Lamiaceae. Since this is the first year I've grown it, I'm uncertain of its hardiness; however, it reportedly lives as far north as Siberia, so it should be exceptionally hardy. A related species that has flowers almost identical to I. excisus can be seen here.

Our plants bloomed (without me noticing) in the summer of their second year in the garden. They have stayed with us for years now, so indeed they are hardy here. The coolest photos (quite literally) were taken of this plant in its dormant state, taken one frosty morning in early December.

But this is not just any dead stalk - I was very pleased to find that this is one of the plants that promote the formation of ice flowers - a first in our garden! According to sources I've found, ice flowers are formed when still-green tissue inside the stem cools to near-freezing. The expanding water squeezes out of narrow slits in the stem tissue, and freezes upon contact with the cold outside. As more water is extruded, it forms a ribbon that curves and curls as different forces of gravity, expansion, and contraction act on them. The ribbons are striated, due to variations in the slits' widths, and together, several ribbons can combine to form intricate bows and other pattens. Quite the lovely find on a cold, sunny morning walk!

Isodon excisus

Another bonus: I knew about just one plant of this species in our garden, and thought I had lost a patch elsewhere. On seeing the ice flowers on the known plant, I walked over to the place where the others had seemingly disappeared, and sure enough, I found about five plants showing off their ice sculptures. The first time I've identified plants by this method (and quite possibly the last)...

Isodon excisus
Isodon excisus

We left this plant behind in our Pennsylvania garden (and wish it well); we don't grow it in Houston.

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Seed-starting details for this plant

  1. Seed from '04 trade. Baggy 70F with light (96%G, 3-6d)
  2. Seed from '06 garden. Baggy 70F with light (75%G, 3-8d)
  3. Seed from '08 garden. Baggy 70F with light (67%G, 3-11d)
  4. Seed from '08 garden. Baggy 70F with light (no G, 15d)

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