I’ve had fairly good luck with a mix consisting of 2-3 parts coarse sand to 1 part perlite fines to 1 part fairly fine garden compost—I generally use a store bought “Gardner & Bloome” compost mix consisting of composted bark, “forest products” (whatever that is) and a bit of some variety of manure. I try to avoid peat in my seed mixes as it seems to encourage pathogen growth in my climate. I had terrible luck the one time I tried coconut coir—most of the seeds I sowed in that mix rotted before sprouting, and none of the ones that sprouted did well. I’m not really sure why this was the case, but I haven’t tried coconut fiber again since. I live in a very wet climate (east of Seattle, WA—50 inches of rain/year) where humidity is often high, especially when temps are chilly. The high proportion of sand reduces the water retention capability of the mix, to try and discourage unfriendly microorganisms that enjoy our cold/wet conditions. If you live in a drier/warmer climate you might want to up the organic content a bit to help retain moisture. I’ve used this mix to germinate amaryllids, lots of South African and South American irids, lilies, calochortus, trilliums, assorted asparagaceae, aroids, gesneriads, and a variety of alpines as well even some trees and shrubs. It seems to work best for seeds with fairly quick germination—the compost supplies some nutrients which the seedlings can take advantage of but they do leach out with regular watering and will be gone by the time long-dormant seeds get around to germinating. I’ve had particularly good success with South African iridaceae... probably 80-90% of the 200 or so species of Gladiolus, Babiana, Hesperantha, Sparaxis, Ixia, and Geissorhiza I’ve tried have done well in this mix. The other 10-20% either decay before sprouting or sprout and then languish and eventually die, but I suspect these have had more to do with my growing conditions (temp/humidity) than the substrate. On Mon, Nov 11, 2019 at 6:32 PM Jane McGary <janemcgary@earthlink.net> wrote: > Yes, I still use about the same mix for seed sowing. However, both the > sand and the pumice include fines, which is not the case when one buys > them "washed." I don't think unwashed pumice is available except right > in the area where it's extracted (here). I would not use coir in a > compost, but perhaps that's all that is available in some parts of the > USA. I do use a soluble fertilizer at low strength once the seedlings > are well developed. I used to use forest humus as an ingredient in bulb > potting soil, but I moved and no longer have my own forest, so it's hard > to know what to use. I don't have the equipment to make my own leaf > compost. I buy something with "municipal compost" (composted yard > debris) and screen out the bark. I don't like to use any bark product > when growing bulbs that have a dormant period, because the > microorganisms that attack the bark also can attack the dead (but > important) tissue of bulb tunics. For our English correspondents, no, we > don't have "John Innes mix" in this country. > > Jane McGary > > On 11/11/2019 5:59 PM, M Gastil-Buhl wrote: > > After much googling for the ideal seed starting mix for bulb seeds, of > > course I arrived at the PBS list, where I should have begun. In November > > 2008 Jane McGary wrote > > "my normal seed mix, which is equal parts sharp sand, screened peat, and > > ground pumice" > > > > Jane do you still use that same mix as 11 years ago? I notice it contains > > no compost and so will have nearly zero nutrients. That seems appropriate > > for long germination times where N-P-K will just grow algae, accumulate > > salts and do no good for the seeds. I assume once seeds are growing that > > you apply fertilizer. > > > > > _______________________________________________ > pbs mailing list > pbs@lists.pacificbulbsociety.net > http://lists.pacificbulbsociety.net/cgi-bin/… > _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/…