Finally, this month should see the end of our long and very cold winter! Your deciduous trees will be coming in to leaf (if they haven’t already) and you should have enjoyed some blossoms from such plants as prunus, crabapples and flowering quince.
As the new season growth commences on trees that have been dormant over winter, the work really begins. Pruning is so important in spring. If you have any cherries, apricots or quinces prune the foliage which develops very quickly after flowering. This will increase branch development, as well as helping to keep your trees looking tidier.
Carefully watch the development of maples in general and Japanese maples in particular. As the second pair of leaves develops either pinch them off when they are quite small or use tweezers to do this. If this practice is not done, long internodal growth (long spaces between leaves on a developing branch) will occur. An added advantage in doing this is that there will also be back budding.
Most species of elm can be pruned back to two or four pairs of leaves to increase ramification. It is a good idea to then allow six pairs of leaves to develop and then cut back again to two or four leaves. Take more care though when pruning Zelkova, as they resent being pruned back too hard and a trimmed stem may die back past the point you planned.
Spring pruning is not over yet, as evergreens are growing rapidly: privets and conifers will need lots of attention. Remember that if there are any parts of a tree which are not developing well, do not prune them until that section has become stronger.
Check any wiring on your trees carefully, as branch thickening during spring may lead to wires cutting in more quickly, leaving unsightly scars behind. It is generally better to not wire during spring for that reason, particularly with deciduous species. Remove wiring from a tree if the branch has set, or replace wire in the opposite direction if it has not.
With so much active growth happening, it is time to start fertilising all your trees (except for recently repotted ones, leave them for a month before fertilising). Whether you fertilise fortnightly at half strength or monthly at full strength or every three months it doesn’t matter, but fertilise you must, if you want optimum growth and health of your trees. What is essential is that you follow the directions from the manufacturers and do not over fertilise.
As always, make sure your trees do not dry out. Trees in very active growth, particularly if they have been recently repotted, can suffer damage to their foliage or even die if moisture is not readily available.
Editor’s Note: The fertilising regime at the National Bonsai and Penjing Collection at the arboretum in Canberra is 30mls of Powerfeed combined with 30mls of Seasol in 9L of water fortnightly.