Mystery of the invasive knotweed

Ketzel* Levine's book was recommended by Martha (I think), so I ILL'd it. For each season, she recommends a list of plants, especially those that thrive in her zone 8 Portland (Oregon) garden, giving each a double page spread complete with watercolor illustrations.

Some of her comments are too hokey for me, but I appreciated listings of plants I'd forgotten about or didn't know. Made notes of Primula sieboldii (good in dry summers, I have been longing for those high-stalked primroses you see in England), Ekianthus (spring-blooming shrub for shade), Clethra (though it prefers moisture), Kadsura japonica 'Chirifu'
(an evergreen vine for shade), and sweet box (Sarcococca).

Then she noted controversy about Fallopia, which she lauds as "big, leafy perennials that are ornamental from day one...but because of the grossly invasive nature of this genus, no discussion of the two variegated forms is possible without raising hackles high."

Could this be related to the dread Houttuynia? This is the incredibly invasive plant that Dianne B. rails about in her book. Judy offered me something in her garden that reminded me ominously of this plant, though she swears it's not invasive at all.

Here's Judy's plant in a shady spot with some impatiens:
 


and here's a picture of Fallopia, aka Japanese knotweed:


and then here's a picture of Houttynia:




Are they all the same thing? The mystery deepens...but as someone who has bishop's weed, loosestrife, mint and lemon balm already, I'm not going to jump into this, whatever it's calling itself.


*So, I always thought her name was Ketza - comes of listening to her on NPR instead of reading...