I have what I think is a Southern magnolia, whose a few limbs have expanded over my roof. I'd like to try to make use of the growth on it instead of just cutting them off, by an air layering. I've done a few on newer growth off the tree, but these are larger and older. Included is a picture of one of the overhanging limbs. I'm wondering if an air layer might take at the thicker, lower point (1 3/4" diam maybe) before the split to two thinner (but long-ish) branches, or would I have better luck with making two instead above the split? Or is the growth too old to take? I did have great success last year with a mature three limbed leader off a ficus, so on that it worked on a fairly mature tree; but this magnolia has thicker branch diameters, and likely well older growth than the ficus branch. Thx

Where you live, air layers of larger branches should be started in early spring, though there is some leeway if the plant being layered is genetically very vigorous. Reason: it takes time for enough roots enough to sustain the plant after separation to form, and the layer can't be left over winter, even if you use a pot/soil instead of sphagnum moss as the rooting medium. Too, branches used as propagules should be of the highest vitality on the plant. Weak inner branches or branches on the north side of the plant should be avoided unless they are near the top of the plant where they get plenty of light. How much stored energy the propagule has plays a significant part in determining the probability of success.
There is nothing to stop you from trying, but I'd go with the smaller branches because of timing issues. I do a lot of layering, in case you want some suggestions that will increase your success. Pre-blanching at the layer site (when you have the luxury of time on your side) predisposed the plant to form root initials even before you establish the layer, so you'll likely want to know about that if you plan on going for a thicker branch next spring.
Al