Illustration by Sergio Cuan from Michael’s Bonsai Heresy
Today’s post is timely (it is spring after all, at least for some of you), and it’s by Michael Hagedorn, one of the best when it comes to bonsai know-how. Michael is, among other things, Mr. Crataegus Bonsai and the author of Post-Dated, the Schooling of an Irreverent Bonsai Monk, and the more recent ground breaking Bonsai Heresy. I could say a lot more about Michael, but rather than me prattling on, we’ll let Michael speak for himself (from his Crataegus Bonsai blog):
Some plants really do need fertilizer right out of the gates. If you plan on decandling black pines, just before they begin visibly growing is the prime start time. Chojubai could use some early in the growing season as well. But those are rare; for the most part, for developed bonsai, let them grow a beat of time before fertilizing. Maybe wait a month or two.
We have, though, many undeveloped, younger bonsai. Many of those can benefit from some fertilizer in spring as they begin growing. This translates into greater caliper, more buds, faster build. Very old collected trees don’t need lots of fertilizer; for these a mild push is all they need, later in the spring.
I’d encourage the use of a slow release of some sort. Organic fertilizer balls or cakes are excellent (or perhaps small amounts of osmocote or apex, synthetic slow release fertilizers). Liquids work, but are labor intensive to get the right dose to the right plant. Another advantage to solids: if you get frequent rains in the spring and fall, with wet soil for weeks, the bonsai still get fertilized. If the pot is sopping wet you’re less likely to want to water in fertilizer.
Check out Michael's books while you're here: