I've never seen anything like you've described, so IDK. I'm assuming you can't snap a pic because you sold the home, but do you have an old pic from way back when you can scan? Also, what is your general location/zone -- that can sometimes help narrow it down in terms of what grows where.

Where did your grandmother live? Knowing the area and growing zone may help someone identify the plant. The " stalks well over ten feet tall" sounds like she may have lived in a warmer area.

These are the bamboo-like shoots at the end of season.

And this is what they look like in mid-summer.

O, honestly Jay, I get that this has been a horrible plant in your garden...and even that it is invasive in some states...but this is a stalwart of hardy tropical gardening here in the UK (along with fatsia, tetrapanax, catalpa, eriobotrya, canna, musa and so on. Either pollarded or coppiced every year, it is grown for the fabulously architectural leaves - not a seed survives (and I have never once seen a seedling or sucker around the park trees in my town). TBH, it is far from vigorous here (it is increasingly popular as a municipal tree along with robinia, another somewhat dodgy choice,. imo). Loads of annual die-back which makes it a bit graceless and lumpen. I would not choose to grow this as a tree but I have seen it looking amazing (and holds up to winds far better than musa, for example). Anyway, Devon -what do you think? Do you especially enjoy it, bearing in mind it requires a fair bit of maintenance and may indeed cause issues further down the road? What sort of a garden would you like? And what about gardening do you enjoy?

So, horses for courses - after 15 years doing design and build, I have a vicious hatred of bamboos...all of 'em, regardless of whether they are clumping or not...but I should try to be more positive and encouraging (I tell myself, daily, after issuing yet more withering sarcasm and hard-eye at radio, TV, allotment neighbours, road-drivers, authorities everywhere.)

I drive by a home here in Central Illinois that has this plant and marvel at its uniqueness. So bare and odd thru winter. Then these big leaves thru the summer--I don't think I've seen blooms on it (it's in quite a shady yard). But every year or so, another stem comes up. Hers are not as tightly placed as yours seem to be, altho maybe a 8 inches apart. She said hers came from her grandmother and did not know its name.

I've seen it beginning to self sow in London. And it's spreading in Italy. I don't think it's that the UK is smaller than the USA but that, until now, our summers have not been hot enough to set or germinate seed for some species. For example in all the years I've had a Hibiscus syriacus I have only seen one single seedling. Tree of Heaven is another one which rarely used to self sow but I have it noticed it beginning to.

Thank you for identifying the plant, even though you think migration is solely based on one degree of temperature. Your indoctrinated political rant about "climate change" (climate changes every microsecond, naturally... because that's how nature, weather, and climate work) is quite silly though. You sound like you're saying ALL migration takes place due to people, animals, and plants that can't survive a single degree difference in temperature... which would mean they no longer exist to talk about. Or one of those crazy people who thinks we should "get rid of all c02," which would kill all plant life on the planet. Look up how much c02 your country puts out vs what can be stored in trees alone- disregarding ALL other plant life.

As far "invasive" and tricky maintenance... I don't remember that being the case at all. I live in Vermont, and the patch that grew on my grandmother's property stayed quite well in it's area. There were a self-sown spots within 2 or 3 feet of the main bunch... but I always just ended up mowing them down, and it was never an issue to keep them from spreading. As far as growth goes, maybe my grandmother did most of the work necessary to put the plant on cruise control. In the 8 or so years I lived there, I never had to do anything at all to encourage or continue growth. I don't have a lot of full sun areas here at my new place, so I may have some troubling figuring out a spot and getting started, but I do so love the look of the Empress Tree, the shade it provides, and the incredibly light wood left behind each year. I tried to reply earlier, but apparently this site on my phone will only let me type one word... then replaces that word with the next one I type.

To whom are you addressing this? I don't recall anyone mentioning politics? Location is everything. It might be too cold for Paulownia seeds to germinate in Vermont, but the tiny seeds can hitch a ride stuck to cars heading south? There's a county near me that has a Hedge Parsley epidemic because the weed mowers spread the seed. You shouldn't crap on people who are trying to help you out! I apologize for coming on a bit strong without taking your memories of your grandmother into concideration. It wasn't intentional, I really was trying to be helpful.