Today I pricked out the last of this year’s black pine seedlings. Correct treatment of the roots at this early stage pays dividends later with better rootsystems to give superior nebari on your bonsai. These photos show my methods. These are quite advanced seedlings. Another post shows my technique with much younger seedlings but it is possible to pot up seedlings at any stage. the important thing for future nebari is to restrain vertical roots and promote well branched radial roots so cut downward roots hard.
before cutting roots
After trimming roots
Seedlings with strong rootsystems are easy to work with.
Some have sparse roots but should still be cut back to encourage more lateral roots.
sparse roots
I usually trim the tops of strong seedlings when pruning the roots. I am not sure whether this is strictly necessary (another research project?) but has been generally recommended by bonsai experts as a way of taking the stress off the plant while it has a reduced root system. I am now using the shoots I prune off as cuttings. see previous post for more about this.
before trimming the top
cut back excess top to reduce stress
Spread the roots as best you can when potting the seedlings but they can be rearranged next year if necessary then water them in well and place the pots in a sheltered location for a few days for the plants to adjust and recover.
Seedlings should be watered well after potting up
Good Info here. I was under the impression I should wait until Spring to re-pot, as Autumn is when the nutrients are headed to the roots for winter. Will these be kept in a sheltered area over winter to protect them from the frosts and therefore reducing the stress of the root prune or will there be enough time for them to recover?
this website is based in Australia- so autumn there would be equivalent to northern hemisphere ‘s spring.
Hi Ross, Autumn here is the same as autumn (fall) in the northern hemisphere (weather cools, deciduous leaves coulour then fall from the trees, etc) but it does occur at a different time of the year. My deciduous trees are just starting to colour up now at the start of April. I do my spring repotting in August and September.
Hi Neil,
I have not heard of repotting in autumn? Is this a technique you have done before? what are the benefits over spring repotting?
Hi Kane, We need to differentialte between young and old plants when talking about repotting. I repot SEEDLINGS and CUTTINGS at any time of year as in this post. This is quite safe, in fact much better than leaving them in community pots for extended periods. I have not repotted older, advanced bonsai in autumn yet but some very experienced and respected bonsai growers routinely repot CONIFERS in autumn and have as good or better success at this time of year. I only have a few conifers as bonsai at this stage so have not needed to try this yet.