----- Original Message ----- From: "Stephen Putman" <putman@pobox.upenn.edu> To: "Pacific Bulb Society" <pbs@lists.ibiblio.org> Sent: Friday, March 23, 2007 12:28 AM Subject: Re: [pbs] Stem-less Spring Bulbs > I have been rather curious about a related matter, that being the issue > of stem length at blossom time for Hippeastrum. Some years a particular > plant will flower with a nice long stem, and then the following year > have just a short and rather unattractive blossom presentation. > Somebody must have done some systematic work on stem elongation in > Hippeastrum for all the flower trade that goes on. Who knows where this > information might be found? Can't tell you where to find more on this, but lately I have been reviewing the info on "DIF" in the Ball Red Book as I try to figure out why my 'Minerva' bloomed last September with no stem at all and looked to be going the same way this month. (DIF refers to the difference in temperatures between night and day. Positive DIF is when the day temp is higher than the night and negative DIf is the opposite. Positive DIF lengthens stem and negative DIF halts or slows that lengthening.) The flowers last September were pefectly formed and gorgeous, but only the pedicels and buds poked out of the bulb neck. And I think Minereva may be sensitive to negative DIF. I had my potted Hippis outdoors while the days were still a bit cool (say 55-65F) so they could get some sun and I took them in at night, since the nights would have been too cold for them. This inadverdently gave me negative DIF. I noticed that scape lengthening seemed slower than usual, but once days jumped into the mid 70s and 80s (ah, spring!) with the nights in the 50s and 60s and I left my plants outside, the scapes seemed to get back to business. Minerva grew almost 1/4" over one night. And that brings up another anecdotal reflection. A friend and I were discussing how we had both noticed how much growth our plants' scapes made overnight as opposed to over a day's time. So, if it is true that Hippeastrums do continue to grow as much or more at night as they do during the day, the night temperature may be crucial to proper scape growth. Much of my collection is made up of modern large-flowered hybrids and they seem to prefer days 75F and above with nights maybe 5-10 degrees cooler. I don't think the sunny days weren't especially helpful due to the too-cool temps. The negative DIF was also working against them.The color on some of them (and some Crinums as well) looked a bit chlorotic, a little too chartreuse for comfort. Negative DIF again. Now, if I could find the website where I saw daily temps archived for my area from last year, I might check to see if there were some sudden cool day-warm nights thrown in there that may have hit Minerva at a vulnerable moment. The effects of neg and pos DIF take effect immediately so the plants responds one way or the other right then, no lag or drag. But aren't other plants known to never get over a chill at the wrong time? Plenty. Just speculating, you know........ Robert.