Can anyone clear this section up for me? I'm not certain about the node thing ESPECIALLY the part I will bold: P
Pruning Below or Between Nodes
Pruning between nodes gives a different response, and in general produces atypical, juvenile growth. Juvenile growth arises not from a dormant bud at the node, but from an adventitious bud along the internode at the base of a needle. The color is typically bluer, the needles finer, stem slightly wavy and thin. After a year of two (after the needles are gone) this juvenile growth will be indistinguishable from stems of mature growth.
This kind of pruning can be thought of as 'forcing growth', or forcing the stem to back bud. It is pretty reliable as long as the needles are still present on the remaining stem section. Removing the node and its terminal buds removes the flow of auxin that keeps the adventitious buds dormant. This releases the buds at the base of the needles, and often it releases almost ALL of them, so a typical response is produce a 'broom like' effect with very many shoots just below the cut, one for each needle.
This kind of pruning can be used when you have branch or branch section in just the right spot, but the internodal distance is too great. To save and use the branch you have to make a bud break somewhere in the middle so you can prune it back. The object in training any of the branches of a black pine is to produce a series of forked branches with the length of each fork DIMINISHING as they proceed toward the end of the branch. This is usually accomplished by timing the secondary candles as explained above. However, sometimes you blow it, or you acquire a pine with branches in the right position, but with internodes are too long, particularly the first internode.
If there are still needles on the section you want to stimulate, simply cut the branch off just before the node (whorl) at the end of this section. I usually do this in late winter, but I don't think the timing is all that important. This is another fuzzy area for me, and I will probably know the answer in another five years. I did learn one new trick though. A colleague of mine prunes in late winter as I do, but doesn't prune the needles until later, usually in July. Removing the tips of the needles further reduces the auxin flow and will help in releasing the adventitious buds. It certainly works for him, he creates branch stubs with little fuzz balls at the end of them after one year. So cut the needles in half on the remaining branch stub in summer. New buds will be evident by fall.
If the section you want to stimulate doesn't not have needles (older wood) you cannot use the above procedure. Conifers are very sensitive to the hormone feedback system between the roots and the branches. I think this partly due to the long lag time (much longer than deciduous plants) for bud break. Strongly growing branches send the hormone auxin to the roots (actually specific roots) which stimulates those roots to increase their growth to support the new foliage. Roots thus stimulated send more of the hormone cytokinin to the branch to stimulate stronger branch and foliage growth. If the roots fail to receive the auxin signal which is produced by the terminal buds and foliage, they will cut off the cytokinins and eventually wall off the area causing the branch to die.
This is what we call 'keeping a sap line' in conifers. It is true of some other plants as well, but is critical for conifers. That is why you hear the warning about always leaving some foliage at the end of each branch when pruning pines and junipers.
So what do you do to stimulate buds in older wood where the needles have long since fallen? You can start 'forcing' the growth back by starting farther up the tree, or farther out on the limb. Prune just ahead of a node that DOES have needles left on it. This will stimulate bud breaks before it. In addition it will often produce a very few adventitious breaks on the older wood in the internodes (or nodes) in the needleless sections. Once these buds break, be very careful with them, they will be extremely fragile, and it probably won't happen twice. Let them grow undisturbed for two years, then begin forcing growth on them. After a few more years, you may be able to force growth back even farther by hard pruning of these stems.
The key to a strong bud breaking response is to have a very vigorously growing plant. There must be a strong root system and strong upper growth as well. Before doing any of this work, invigorate the plant by repotting it, or planting it in the ground, giving it optimum water and sunlight, and fertilize it adequately. Alternate heavy pruning years with light pruning years to allow the plant to 'pump up'.
