[APWG] BURNING Saharan mustard, seed germination & Seedling densities

[Craig Dremann]

Dear All,

BURNING MUSTARDS: Some excellent new pictures of burning Saharan mustard
plants, taken by Meckenzie A. Helmandollar from Globe, Arizona at 
http://www.ecoseeds.com/mustards.globeARIZ.html --Flame ON!

SEED GERMINATION REQUIREMENTS: Also, Meckenzie and I have been working
out the details of Saharanm mustard germination, and stumbled on two
dormancies in fresh seed, that I haven't seen reported in the literature
before: 

1.) Cold-moist stratification requirement until August.  

Fresh seed of the Saharan mustard has an interesting cold-moist
stratification requirement until August 1-7th of the same year that the
seed was produced.  After the first week in August, the seeds will
germinate at will at room temp. without any cold-moist stratification
requirements.

The June-August 1st. dormancy is to protect the seeds from sprouting,
due to summer showers, so the seed is only sensitive during that period
to adequate moisture plus cold of between 33 deg. F. and 40 deg. F., for
about 24 hours.  

If the temp. is freezing or below, however, seeds remain dormant.

2.) Minimum Adequate Moisture requirement for a minimum amount of time,
to keep the gel seed-coat saturated, in order to start germination. 

Along with the dormancy in the seed before August, there's also a
moisture-level dormancy related to the gel-material of the seedcoat.

The Saharan mustard seedcoat, when wet, forms a gel, similar to chia
seed, sweet basil seed, or garden cress seed.  However, if the moisture
surrounding the Saharan mustard seed isn't at a high enough level for a
sufficient amount of time to permanently activate the seedcoat
gel---then the gel shrinks back into place, and the seed waits for a
period of adequate moisture.

Furthermore, when the seed is in its early stages of germination, the
gel becomes a potential moisture-reservoir that the roots can draw from
in case of a dry period. 

Viewing this seedcoat gel's activity and strategies under a microscope
is very interesting.

SEEDLING DENSITIES. The narrow stem and small size of the seed-leaves,
allows for a very high seedling-density. 

When seedlings are one inch tall,  they can pack in an average of 25
seedlings per square inch, and a maximum of about 56 seedlings per
square inch, which translates to 175 million to 322 million seedlings
per acre.

Of course, as the seedlings grow, they weed themselves out to space
themselves at a minimum of about 8 inches apart, or a maximum of about
19,000 plants per acre.

DR. POWELL'S chart, Slide #11 of the Saharan mustard's spread and
eradication requirements, at 
http://www.ecoseeds.com/mustards.html#anchor224

Sincerely,  Craig Dremann (650) 325-7333