are you.. 100% sure.. they leaf out.. consistent with the rest of the plant ...

bark color changes with maturity ... but its way off color... makes me think.. i would wait until it releafs.. before i would decide what to do with it ...

thats some mean pruning.. on the old branch.. that used to go out toward the house ... when you truncate a huge branch.. out at distance.. it is not uncommon.. to start the plant suckering ... can you tell us more about all that...

and perhaps an upright pic of the whole ... its upside down for me ... but not after clicking ....

ken

You don't have to cut them back to get branching, and this being a magnolia it would be better if you didn't. As it is a shrub it would be just as well to let it renew itself from the base like this - except where individual new basal stems are not going to be able to enlarge without conflicting with existing older trunks.

There are several selected varieties of magnolia seiboldii such as 'Colossus' and 'Michiko Renge'. These are grafted or, more commonly, budded onto ordinary seiboldii understock. It's very likely this is what you have and the growth emerging from the base is coming from the understock. It will not be the same in flower quality or growth characteristics so should be pruned out.

I do not agree that it is very likely this is an example of one of the named forms, in fact the odds are against it as these are not seen nearly as often on the market as stock sold simply as the species. However, it depends, of course on what is the case in this particular instance. And since it can be seen that the specimen shown here was limbed up in the past - not something I would do with a low-forking shrub myself - apparently it is a situation where basal shoots are not wanted anyway. And there may not be room for the ones shown to develop fully, even where otherwise it might be desirable to let the shrub continue or renew itself from the base. So we still come back to pruning the new ones out.

It should be fairly easy to tell if this is the straight species or a named variety budded onto an under stock. Gently scrape away some of the mulch at the base. If budded, you should be able to see a definite swelling on the trunk where this was done. If the shoots are emerging from below the area of swelling, they are coming from the understock and you almost certainly have a named variety. No swelling and you have the straight species.

The straight species may well be more common in commerce on the West Coast, but in the East the opposite tends to be the case. Since we don't know if the original poster's Washington is the state or DC, both named variety and straight species are possibilities.

"NW Washington" is going to be Washington State.

Perhaps, but NW Washington or Washington NW are also commonly used designations for the area of DC north of the National Mall.

As the picture is upside down if they had posted NW WA one could then argue the site was in Australia.

Thank you for your answers. I live in the Pacific Northwest, close to the Canadian border. I removed some of the mulch as suggested, it looks like the three canes are growing off a huge root. I am attaching a picture of it, maybe it will clarify whether we are talking of new growth or suckers.

As the new photo shows, the new growth does consist of root suckers. Little else, unfortunately, is clarified. I can't detect any evidence of budding or grafting although it might simply be hidden closer to the area of the main trunks. If we assume this is the straight species seiboldii, then I can't think of any harm in letting this new growth remain. The magnolia is already growing as a multi-trunk shrub rather than a single trunked tree, so you might want to try pruning the suckers to induce further branching. If they don't branch you can always remove them at a later time. There is some chance that vigorous sucker growth will adversely effect the older portion of the plant, but again the suckers can be removed in the future.

Normal branching will occur without pruning, ugliness (this is a magnolia) will occur with heading back. The only cutting that needs to be done is cutting off any of the new canes that are not wanted. The one that is already starting to wrap around one of the older trunks, for instance. This same one is also a Siamese twin with another, down at the base - there is not room for both of them to enlarge.