When the stems of the seedlings have turned a violet/purple color it is time to remove them from
the seed trays, cut off the new roots completely and transplant the seedlings into individual four inch
nursery pots. I believe this usually takes four to six weeks from the time they emerge from the soil.
However, I usually don't pay attention to how long its been because I just watch the stems color. Once
all of the stems have turned violet/purple its time to root prune and transplant.
Here is the soil mix I use to transplant the seedlings from the starter
tray to individual four inch pots. As usual, the basic requirement is that it must be very well draining.
80% inorganic - consists of equal parts of three different sized components. (see image below)
- Well gravel (filter sand) #2 small size
- Well gravel (filter sand) #3 medium size
- Crushed granite (Chicken Grit) large size
20% organic -
- 1/4 inch Screened Canadian Sphagnum peat moss ( use the fines from screening, removing the larger particles )
I used to just use 10% organic, but the summers here in NC can be very hot so I've increased the organic
component to 20% to help with moisture retention.
In the images below you can see where I screen the peat moss and the inorganic material.
Prepare 4 inch pot-
Put a 1/2 inch layer of the largest particle inorganic soil component as a drainage layer. Now fill
the rest of the pot with your new soil mix to about 1/4 inch from the top. I then run water through
the pot to settle the soil.
Gently pull a seedling from the seed tray.
Wipe your blade clean with a paper towel and alcohol before each cut to reduce the chance of spreading
bacteria from one seedling to the next.
Completely cut the roots off with an exacto knife leaving the stem about a 1 to 1.5 inches in length.
Be sure to cut with your blade perpendicular to the stem to make a straight cut. This will promote a
nice radial pattern of new roots at the exact same height on the trunk.
I use a wine cork to create a hole in the soil for the seedling about an inch deep.
Fill the hole you made with the wine cork with the smallest inorganic soil component
The smaller particle soil size helps hold the root pruned seedling in place and promotes a finer new
Dip the seedlings newly cut stem into rooting hormone.
Using a chopstick in one hand and a seedling in the other guide the seedling into the soil leaving
enough stem above the soil line to hold the needles above the soil.
Gently water being careful not to disturb the seedling.
Place the newly planted seedlings in a shaded area for approximately two weeks. After two weeks start
introducing them to some morning sun. I water as needed, but with this soil mix its pretty much everyday
throughout the summer. In the past I've probably been over cautious with regards to sunlight, but
these seedlings can get roasted very quick in direct summer sun. Choosing to err on the side of
caution has served me well so far.
About four weeks after root pruning and transplanting I start to fertilize with fish emulsion
once a week through June. I stop fertilizing for the month of July (too hot, no growth) and continue again from August
You'll find that the newly root pruned and transplanted seedlings grow very little the first summer.
There will be a little extension during the fall and winter. However, the next spring you should see
real signs of strength and the formation of the little pines first candle. By the end of the second
summer your seedlings will almost triple in size... from 2 inches to 6... not much, but it's a start
I believe the Bonsai Today Masters' Series: Growing & Styling Japanese Black and White Pines book describes
possible doing a second root pruning to completely remove the roots again. I have not tried a second complete
root removal. I think just one provides excellent results.