We recently moved to Oregon and we have a beautiful Magnolia Sieboldii in bloom in our front yard that is about 10 feet tall, 5 feet wide. Some of the branches are crossing over the center from one side to the other - (My background is growing roses so this concerns me.) The tree is very dense. Should I prune these branches this fall to allow air flow and leave the older branches? Should I leave the twiggy branches at the bottom, or try to creat a more "tree like" shape? Or the better question might be should a Sieboldii be pruned at all? Thanks for your help.
We do not usually prune a Magnolia unless we have to or we want to make a change in the appearance of the tree for later on down the road. Some people will prune their Magnolia even when we advise them not to, so we go along with them and tell them it can be done but not without a price. The price when we whack into old wood is that it can take a few years to get adequate regrowth and in some Magnolia forms we do not get any regrowth to appear from below our cuts. Since we do not have a photo of your tree to go by, I would leave the tree as is unless the crossing branches are rubbing each other and are causing visible signs of bark injury or you are seeing a few fused branches or you are seeing some twig and branch dieback. Look at some of the photos of the Magnolias such as Sargentiana robusta in the Botany Photo of the Day pictures to see how a well shaped Magnolia looks like. We see dense and full growth but none of that growth is obtrusive for the tree and does not prevent sunlight from entering the centers of the trees. Note: there are photos of Sieboldii posted in a few other sub-forums in the UBC BG forum as well. If we have to prune a Magnolia we start in the center of the tree such as yours as much of the flowers will be seen on the outer and top portions of the tree more so than the inner portions. Still, with every cut you make you will lose flowering ability for next year and perhaps a few more years. It is better to let someone with trained hands work on your Magnolia that has worked on Magnolias in the past. The latter becomes rather important in that we do not prune various forms of Magnolias the same way as we can others. As an example, we do not prune a Sprengeri or its forms like we would prune or prune to shape a Stellata type. One we can prune all we want here and we should get some new rejuvenate growth and the other we may not get any new growth to compensate for the wood we just took off. Sieboldii is in the middle of these two scenarios as we can prune it and get some new growth to come back but it will not be nearly as soon as most but certainly not all Stellata and Loebneri type trees will here. Where you are located you will not see the new growth on Sieboldii come back for you as soon as we will. Best time to prune is right after the tree has bloomed for trees grown around here as then we have time until early October in most years for the tree to force out new growth. The lower branches to achieve height in the tree or more clearance from the ground can come off or be pruned back anytime now while the tree is still in leaf.. Jim
Doesn't need any pruning for health's sake, plant kinda big (far along) to being doing structural alterations now. If there is a branch or two that are driving you crazy you can probably remove those, if not too big. Keep in mind that each pruning cut is a wound, an opening in the protective bark. Deciduous magnolias seem to be a little weak about responding to openings in the bark, pruning cuts often looking more like sores than with some other kinds of trees.
Thanks, I think I'll just leave most of the tree as is and remove the very few cross twigs that tangle with the established branches and would allow more light/air into the center area. (These twigs are about a third of the size of a pencil) that go across the middle of the tree and really don't contribute anything to the form of the tree. The tree has four main trunks that branch out to eleven tall branches that come together at the top. Each have growth off them which is were the bloom seems to be, so I won't touch those!
I wouldn't worry about the light and air thing, this is not generally applicable - most trees and shrubs have nobody out in the wild 'opening up their centers'. Abnormally mildew-susceptible garden forms of such things as rose bushes and grape vines are supposedly assisted by some thinning to promote drying of the foliage. However, I have to wonder how much effect this will have on a plant that is liable to become covered, such as a Gallica rose or a deciduous hybrid azalea. Probably much of the time one ends up with a mildewing shrub additional marred by a hole in the middle, instead of one that has been protected by 'opening up the center.'
