I planted a Dusty Miller last year, and it is crowding my other plants already (invasive?). The flower shoot just took off, and is laying on the ground. I want to throw the plant away, but I've heard you can cut the flowers off and just enjoy the leaves. I don't know if that would qualify as a "problem" or not, but it is a problem as far as I'm concerned. Here is my dusty miller (you should be able to click on the thumbnail to see a larger picture, if I got it right):

Hope this helps,
Martin

Alyssum 'carpet of Snow' is capable of seeding around quite a bit, as are lupines that I am familiar with. Money plant reseeds well but I like it better.

Second on the forget-me-nots - I've learned why they're so-named and it's exactly as plantknitter describes them. They're lovely in the spring coming up through the roses but oh man, when they go to seed my poor pups go ball-hunting and come out covered in those sticky seeds. Not good.

Sue

I pull Forget Me Nots like weeds but haven't had any huge problem with alyssum reseeding at an alarming rate.

I think violas will reseed very readily as well.

Black Eyed Susans are fairly quick spreaders but are easy to pull and so cheerful, I hate to say NO to those.

columbines ( some of them) reseed a lot, but I don't know your particular variety listed.

I love the sounds of your list- some of my favorites are on there. What a nice thing to help your folks with! Good luck on your planning and planting.

If they can't do too much gardening anymore maybe they shouldn't be taking on a perennial border at all.

"Lovely though they are, most perennials require more grooming than woody plants and most need dividing. Though even the laziest gardener will probably find room for a few perennials, not many of these plants are truly low-maintenance."

Here is a link that might be useful: The Easy Garden

None of the listed plants are considered invasive in the proper horticulture context of the word, although several will reseed very freely. And not all are perennials or hardy enough to act as perennials in our climate.

And I too would question the advisibility of planning an extensive perennial garden for those who may not be in good enough health to maintain it. For a mixed perennial garden to look good and not become overgrown, messy or wildly weedy, it does require regular maintenance - deadheading and grooming, staking, watering and fertilizing, periodic division and a thorough seasonal clean-up. Both forget-me-nots and lupine are highly prone to powdery mildew; lupines are also plagued by lupine aphids. And I'd also reconsider the appropriateness of some of the selections, specially in combination, as a good number of your list prefer different soils and watering approaches than the others.

There is a very informal rule of thumb regarding the maintenance involved with specific plantings - the larger and more long-lived the plant, the lower it is placed on the maintenance schedule - trees tend to be the lowest maintenance plantings, followed closely by shrubs. Most perennials are high on the list with annuals typically listed as the highest. There are lots of lower maintenance perennials available that can reduce the amount of time spent maintaining a perennial garden, but few of them appear on your list. Look for those that are drought tolerant or suitable for xeriscaping, that have evergreen properties, are shorter or compact forms and are known for durability and lack of specific problems. That would reduce your current list down to coneflowers, black-eyed susan (Rudbeckia), shasta daisy, penstemon, columbine, dianthus ("pinks" only), aubreita, candytuft, blue fescue and dusty miller. You can expand on that a lot, but do some serious research first before committing your folks to a big messy headache.

I agree with bboy and Gardengal, an all perennial garden is a LOT of maintenance.

I ripped out my Lupines years ago due to the huge aphids and annual mildew.

Delphiniums require staking and are fussy.

Daylilies are easy care perennials. There are roses such as Knock Out that have no problems and bloom for months and don't require extensive pruning or spraying like Hybrid Teas do. Do want regular water and fertilizer though.

Pansies, Thunbergia, Salvia 'Blue Bedder' are annuals.

Perhaps a smaller list of well chosen perrenials, as recommended above. I tend to like to mass such plants tightly to reduce weeds & increase visual impact. For an example of some well chosen perrenials, try taking a slow drive down Dungeness Drive in the Utsalady neighborhood - you'll spot at least one gem of a yard.