No one has responded yot so I'll just say what I know of it. I've not grown it myself (garden far too small) but my FIL had one and has taken it out. There are also several specimens around where I live. They look very good trailing over a high wall where their habit can be seen at its best but as a standard in a lawn (FIL's situation) it was never satisfactory. It looked scraggly and ill most of the time especially when not in flower. I think it would have looked better in a mixed border with some bolder shaped foliage around it. But I am a bit prejudiced as I seldom like the look of single specimens of anything in a lawn except majestic trees. It also probably suffered from insufficient sunshine where he had it. Ones I have seen get to about 10 feet tall and as wide or wider. If you have not seen it in flower be aware that the blooms are not as large as those of B davidii but are more delicate and lacy. Between the two I would actually pick B alternifolia providing it was well grown and well positioned. But again I am prejudiced since B davidii is basically a weed species here and I find it rather scruffy.

Thanks for your response, flora. I'm still undecided, but the plant would not be front and center. I don't like standards of anything and doubt I would like a standard B. alternifolia.

Growing it as a standard would be repeatedly recommended because of the growth habit lending itself to this. When handled effectively can be lovely in flower but the popularity of B. davidii will probably always make this one suffer by comparison - no long, large spikes of flowers for months at a time.

Even though it is really apples and oranges.

Foliage also is not as nice as that of silver weeping pear and weeping Arctic willow although neither of these have the same flowers as the Buddleja. Like other species in the genus not of the same general character as a true tree or tree-like shrub, with slower, more dignified and tidier growth, long-lived trunk and branches.

Laceyvail, I first stumbled upon one years ago here in NH growing at a wildlife park. There was a lean-to of sorts built into a slope and the shrub was spilling over the roof. It was such a great application for this shrub. It was in full bloom and the bees were going crazy. It was gorgeous and I found myself on a quest. I hadn't realized they were so hard to come by. I finally found one locally years later and have been trying to prune it into a sort of a standard. It has not been that easy but I'm determined to keep working at it. I have mine planted in a mixed border. I am finding it sends up shoots well away from the original shrub. It does look a bit scraggly but I'm hoping as it matures it will fill out a bit. I am enjoying it so far.

I saw this one at the Paris Botanical Garden and this is what I hope to achieve one day.

{{gwi:239701}}

I have one, and my suggestion would be the same as bboy's Train it well and I think it will be a spectucular shrub. I did not do that and I regret it it is a big mess, but a pretty mess. I am going to cut about 3/4ths of mine out this winter and see if I can get a better shape. I hardly ever see them in people's landscapes here in Northern Va I am not sure why; maybe like bboy said people are drawn to B davidii which does give you more bloom time. Mine is never bothered by pest or disease. It stands about 6 feet tall 5 feet wide.

My apologies for responding to such an ancient. The OP may not be around now, but others may read this.

I've grown buddleia alternafolia for over 12 years. Much of the previous comments are true, but the arching purple blossoms make it all worthwhile.

It is not invasive like davidii, but it does root easily enough that if an old plant gets scraggly, you can always shovel prune or cut out the older stems. I have it growing behind a rhody, Bagesson's Gold honeysuckle, and Annabelle hydrangea, so the woody stems are hidden.

We had an unusually cold, snowy winter this past year, and I've pruned back a number of dead branches, but the shrub as a whole is growing strong.

I wouldn't consider this for an entryway or showcase garden bed, but it is dramatic enough from a distance that it is perfect for a wilder bed.