I have had this dilemma more than a few times over the past few years. The ammoniacal nitrogen form often messes with the pH in cold weather sometimes dropping it significantly, and at low temps the ammonia won’t nitrify and can cause toxicity. Using a nitrate form is better in the cold weather, in the greenhouse many of the bulbs are starting into very active growth now and do need some feeding. I recently discovered a product called Peters Dark Weather feed, it’s a 15-0-15 with cal mag and micros that is mostly nitrate nitrogen. I have been doing 50 ppm which is a pretty low dose but the plants have responded very well and I’ve even seen a few nutrient deficiencies corrected despite the temps in the 40’s. Mark Illahe Rare Plants Salem, Oregon > On Mar 5, 2023, at 6:12 PM, R Hansen via pbs <pbs@lists.pacificbulbsociety.net> wrote: > > Jane has a question about fertilizer application with temps still in the 40s > during the day. > > ****I usually apply soluble fertilizer to plants in my unheated bulb house > now. However, we are having an unusually cold late winter: near freezing > every night, and in the 40s F daytime. Many plants are in active growth, > if a bit later than usual. Should I apply fertilizer now, or wait until > the daytime temperatures are a bit higher? *** > > In hort school we were always reminded to avoid fertilizing at least until > the daytime temps hit 50+ because the plants couldn't utilize the fertilizer > at lower temperatures. Whether that is still the case, I don't know, but > have followed that rule forever. > > I too use a fertilizer that's resin-coated and releases at cooler > temperatures. Osmocote works fine in the Willamette Valley and many > nurseries use it, but under controlled conditions, in greenhouses, in can > yards where the plants are in black containers that readily and quickly > absorb heat. > > I tend to use bone meal more than commercial fertilizers, being careful to > stir it into the soil mix and have always grown my plants as hard as I can. > Consequently, I almost never get complaints about a plant dying in someone's > garden (or at least I haven't been told). Sometimes that attitude has > backfired - I should have been fertilizing a bit and paid the consequences, > but fertilizing anything is a fine line and there are so many variables, > almost from year to the next, temperatures, moisture, cold, frost, you name > it. > > When in doubt use a third to half of whatever vague dosing regimen is listed > on the label, unless you have an unusually sensitive plant - our natives > come to mind - that really doesn't like any extra nutrition. Repotting every > couple of years and watching the watering are almost more important than > fertilizer. > > Robin Hansen > Snow again this morning > Southwest Oregon, USA > > > -- > This email has been checked for viruses by Avast antivirus software. > http://www.avast.com/ > _______________________________________________ > pbs mailing list > pbs@lists.pacificbulbsociety.net > http://lists.pacificbulbsociety.net/cgi-bin/… > Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net> > PBS Forum https://… _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/… Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net> PBS Forum https://…