Re: HYB: burrito germination experiment
iris@hort.net
  • Subject: Re: HYB: burrito germination experiment
  • From: L* M* <l*@lock-net.com>
  • Date: Sun, 19 Dec 2010 10:08:34 -0500
I've done it both ways - advantages and disadvantages to both methods.

Advantages to potting all seeds as soon as some start germinating:
-Fewer pots to handle
-Less to think about/remember to do
-Less time spent checking burritos every few days (which can be very time consuming with a lot of burritos) 

Disadvantages
- Pots contain ungerminated seeds, some of which need more chilling (40 to 45oC) while my TB seedlings need somewhat warmer temperatures to grow fast (50 to 60oC when still sprouting, higher once green and growing).
The biggest advantage to picking out individual seeds as they germinate is that the growing seedlings can be pushed to grow faster, so they will be big enough to line out in late March (maybe under row covers) & early April before I get busy with bloom season.
This year's pots will all go out in the sunporch, where this time of year, night time temperatures are usually cool enough to continue chilling, while daytime temperatures are warm enough to stimulate sprouting. Once the first flush of sprouting is over (i.e., no new sprouts for a couple of weeks), I'll pick out the sprouts, put the pots with ungerminated seeds outdoors, bring in last year's pots from crosses that looked promising this year (i.e., IMM X RED ROCK CANYON).
In the past, I usually wait about a month after last sprouts have shown before putting pots of ungerminated seeds outdoors for more chilling, but if it's as cold outdoors in Jan as this Dec (unusual), the sunporch will be cold enough to keep them there. Hopefully enough warmer directly under the lights to stimulate growth on the sprouts, cold enough on the floor to stratify seeds. Ideal world ;-) 

That's the plan anyway.
Because past experience has repeatedly shown more than one flush of germination, I disagree with Chuck on this - they are not all ready to germinate at the same time. 


Why are you potting them all up now rather than putting them back in the
fridge to continue germination?....
 I thought people said they were putting them
in and out the frig until everything sprouted--picking a few out each time.
Betty W.
Prior experience has demonstrated (repeatedly) that for my crosses, 6 weeks, even at the warmer, more optimal stratification temperature, simply isn't enough. And some crosses need a second cycle to germinate - 2 or 3 months stratification, followed by warmer temps (and maybe drying?), then another period of stratification.
Most of the early experiments on timing that I did were with seeds that were first dried, then soaked (panty hose in toilet tank method), then burrito'd at a colder, less than optimal (35 to 40oF), fridge temperature than I'm using now. (check photos archives for graph of optimal temperature for chilling - fruit tree buds, not seeds, but seems to be the same for both)
No idea how long the second period needs to be because I haven't done the experiments. By that time (the second year), the seeds have all been in pots outdoors since the preceding spring. I usually bring them in sometime in January, by which time they have had 2 or three months of another round of chilling, this time outdoors. For this second round, they might only need a month (or 6 weeks), but that's too early for my purposes, so I haven't experimented. By that time, I usually have some seedlings from each cross the prior year to evaluate plus am handling a bunch of new crosses.
So, bottom line, 6 weeks of stratification may be plenty for some crosses, but nowhere near enough for others. Obviously, I only have experimented with a limited bunch of genes here. I have no idea about others.
Some of the info I read about germination inhibitors way back when said that environmental conditions while seeds are developing can affect germination requirements in some species. Seems like the article was referring specifically to heat and drought. No idea if that applies to irises, but something to keep in mind. 


Personally I would think 6 weeks in fridge (after soaking) and then planting
should be all that is needed.

Chuck Chapman


Linda Mann east TN USA zone 7
sun!!

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