Seed germination temperature

Tue, 19 Oct 2010 10:03:58 PDT
Dear Rachel,

Thank you for replying about your experiences with autumnal night time
temperatures. They seem to resemble what mine have been here in September
and October. I have no idea as to the age of the seed and have no reason to
assume they were old. Based on your findings I shall probably stop the
really tedious and time-consuming effort of moving non-germinated containers
into the spare refrigerator each evening. My wife certainly will not object
to that!

In all the years I have lived here this one has been least like the
semi-desert form of mediterranean clime that it normally it is. A cool
summer and a cool, humid fall are quite unlike our typical conditions. In
Sepember and October (your March and April) the days should be hot to very
warm with very low humidity and the day to night temperature range should be
large. All seed are raised in trays outdoors on benches. The trays are
placed within containers that are shaded from sun - when we get some! In
normal years the process works very well.

The concern I had was whether waiting for months in moistened soil mix the
seed would rot. Am I correct in believing that this did not occur for you? 

Andrew Wilson
San Diego 

Dear Andrew
The night time temperatures can certainly play a big role in germination of
seeds. I sowed a large number of seeds this season and I sowed them all in
March (very early fall for us).  Nothing germinated at all in March or in
April and I began to panic. Then we had a really cold spell at the end of
April, and about 60% of the species germinated within 2 weeks. The rest
germinated in May and the last Romulea (some really old seed of Romulea
unifolia) was up by the end of June.  We sow all our seeds in trays and they
are kept in a large plastic covered house which has no heating.  During
March the day temperatures were probably too high, and the nights not cool
enough, and in April, the days were cooler but the nights still warm. The
cold snap we had seemed to do the trick and the seeds all came up.
We sowed Babianas, Lachenalias, many Gladioli and a few odds and ends like 2
Romuleas, a Freesia, a Polyxena, etc. Most were really old seed that we had
thrown out, but some were fresh unidentified species.
Rachel Saunders
Silverhill Seeds and Books

More information about the pbs mailing list