Time to repot. Morten Albek intentionally broke the pot to show this Cork bark Japanese black pine’s dense root mass. From Morten’s book, Shohin Bonsai (Stone Lantern Publishing).
Vacation ended around midnight last night. Still, in light of a whole slew of post vacation demands, I’m going to indulge in one more journey into our archives. This one is from August, 2009, which in the life of this blog, qualifies as ancient.
We’ll stick with our current topic, fall transplanting. With one caveat: opinions abound on how to do most anything, and fall transplanting (really almost any bonsai task) is no exception.
Why transplant in the fall?
If you transplant in the fall your trees can take full advantage of the next growing season. If you transplant in the spring (that’s when most people do it), by the time the tree recovers, you’ve lost part of the growing season.
Why not transplant in the fall?
If you have an early winter and your bonsai haven’t fully recovered from transplanting, then you risk serious damage (or worse). If you rootprune heavily, the risk goes up. If you want to play it safe, fall transplant only those trees that need light to moderate root pruning.
Doing some light rootpruning. From Robert Callaham’s Satsuki Azaleas, for Bonsai and Azalea Enthusiasts (Stone Lantern Publishing).
When?
Fall transplanting season is coming up. When depends mostly upon where you live. There are other considerations too, like the type of tree, the health of the tree, your experience and confidence, how much you need to prune off the roots and more.
A rule of thumb
Six weeks before you might expect an early hard frost, is a pretty good rule of thumb for fall transplanting. However, you can’t be too literal about this. Prolonged late hot spells need to be considered (here in northern Vermont, where summers are more often than not quite mild, this usually is not a problem) as does how much you need to rootprune and the type of tree.
If the soil is old and compacted you need to remove it (see note just below). A hard steam of water and root tools are the best way to get it all off. Because the roots are so compacted, you’ll need to do some serious rootpruning. Unless you are an old pro, you might be better off saving this for spring transplanting. From Bonsai Today issue 17 (all back issues of BT are now on sale). Note, in a discussion last year with Michael Hagedorn, he strongly discouraged washing off, or otherwise removing all the old soil when transplanting. What he did suggest (in regards to a specific tree) was taking half of the old soil off (one side) this time and the other half off next time.
The type of tree matters
Deciduous trees need special consideration as you don’t want to rootprune when they have a full canopy of leaves. Conifers, especially junipers, and broad leaf evergreens are usually safest for fall transplanting, though there are variables here too. If you need more information, try to talk to someone knowledgeable who lives in your area.
Don’t forget aftercare
After transplanting, your margin of error goes down, especially with watering (don’t keep the soil too wet, but don’t let it get bone dry). Misting can help. Avoid midday sun, especially if you live in a hot dry climate.
A freshly transplanted Black pine. The photo is from our Masters’ Series Pine book.