I don't have any experience with those plants but my tallest ones are agastache and false dragon head. Purchased last year and shot up like crazy this year. Hummingbirds love agastache and bees love false dragon head. Oh yeah and I have liatris planted in between which is pretty tall. The colors which are orange, white, and purple look very good together in my opinion.

I do believe my tallest would be Strelitzia nicoiai (Giant Bird of Paradise)--even though they are young, they are about 13-15'. They work for their purpose of providing an evergreen screen outside out the dining room window. Not self sowing.

Other tall perennials are Echium simplex, E. wildpretii (Tower of Jewels)--providing much seed, but self-sowing only a few plants every year. I favor the white simplex over pink wildpretii only due to a color preference away from pink. Great plants, usually getting 5'-7' for me, but can be taller; very long blooming period.

Phormium 'Maori Chief" and P. 'Guardsman' (New Zealand Flax). Not self sowing, but good foliage coloration in the garden. About 5'-6'.

A kangaroo paw (Anigozanthos) with yellow flower stalks 7'-8' tall. The blooms last for about 7 months, but they don't self sow. Great, bright flowers that do not block your line of sight; foliage nice and neat when plant is not in bloom. I have grown to love these plants, even though they need replacing every 3 years or so, due to flowering themselves out .

White ginger also at 7'+. division by rhizomes. Beautiful, fragrant flowers. In bloom from about September through November.

Russelia 'St Elmos Fire', a shubby perennial that self sows, but the seedlings seem to only show up near the base of the parent. Hummer-loved red flowers; almost constantly in bloom. I grow three different red russelias, but St Elmos Fire is the tallest, most upright. I love all of them.

Beschorneria wrightii, which has been in bloom for months, and B. yuccoides plus B. y. 'Flamingo' (should those ever fork over some stalks). Not self sowing/forms basal plants. Something a bit different than everyone else grows.

Ones I expect to get tall (haven't owned them long enough at this point), Kniphofia northiae (Giant Octopus Red Hot poker), some salvias and Lobelia excelsa, which is supposed to get to about 5'.

I ended up having more tall perennials than originally imagined, and I am sure I have forgotten more than a few! :)

My all time favorite is verbena bonariensis, which grows to 5' plus, blooms like crazy, reseeds itself, helped by the goldfinches which love it.

Just cut down a bunch of it last night which has been blooming for 6 or 7 weeks and will rebloom on new growth. Love the way it moves and billows in the slightest breeze and bobs down from the weight of the birds.

My Alcea rugosa (Russian hollyhock) is approaching 7 feet this year. Which means that its hard for me to reach any Japanese beetles hiding on the top most leaves and flowers but so far, I've managed.

I've grown castor bean in the past which easily hit 8 feet here. In places where it's perennial it gets even taller.

joe pye weed, the vernonia is wonderful but I have the dwarf and love it, also have hemerocallis autumn minaret which is very tall in July/august.

To expand on this interesting question, it might be worthwhile to know which tall ones do and don't need staking.

In our garden Thalictrum "Splendide" will reach over 8 feet in height (and for sure needs support).

The tallest we have that needs no staking would be Helianthus "Lemon Queen" which tops out between 5 and 6 feet.

(Extra good info Falcon)

Falcon,

I got a giant bird this year for Mother's Day and put it in a huge pot since I don't think it will survive the winter outside here? Mine is about 5 feet tall now including the pot. Yours are 15 feet tall and still young? Do you think I'm going to be able to keep this as a houseplant in the winter with 8 foot ceilings? Any suggestions for me? I've heard they are fast growers.

Thanks! Sara

Beautiful "Monk's Hood" Sunny.

(My unnamed Aconitum doesn't flower until October...almost for sure because it is in a too shady location.)

My tallest perennials are Acer platinoides (Norway Maple) and Juglans nigra (black walnut), but .....

{{gwi:3277}}

Al

Think 'Spark's Variety' has the most striking colour of all available monkshoods, Rouge.

Yours could be Arend's monkshood. Judging from my garden pictures from last year, Arend's monkshood, (Aconitum carmichaelii 'Arendsii' (or Arend's Group), started to bloom in our garden, last year, in mid October.

aconitum, althea cannabina, agapanthus, rudbeckias (various but some are over 3m), aster cordifolia, thalictrum, lilium speciosum, campanula lactiflora, digitalis (various, but the common purpurea tops 7feet, paeonia delavayii, strobilanthes wallichii, miscanthus sinensis, pennisetum setaceum, panicum virgatum, stipa gigantea,

The Thalictrum rochebrunianum is even taller than the T. 'Splendide'

While I was out this afternoon (before what seems like daily heavy rain) I measured my two "Splendide". Both are at 8 feet tall and have yet to bloom.

(I wonder if it is feasible to do a "Chelsea Chop" on these magnificent plant? Maybe I will experiment on one of them next season)

This post was edited by rouge21 on Wed, Jul 9, 14 at 0:05

More plants to look up--yay!

SG24, that's great! I have those to look forward to--mine are small still except the Liatris, but it's only about 1-1/2 feet tall. I love that color combo, too! Sort of fresh and exotic at the same time!

Falcon, your plant selection sounds fantastic! I'll be checking out their images real soon although they might croak here--got down to 17F the last two Winters.

Rosie, I love that Verbena, too! I'll let it self sow bit!

A2Z, I looked up that holly hock--I want one now. Do you let it go to seed where it lives? I'm not much of a a seed starter. That pale yellow is one of my favorite flower colors.

Shadey, wow! I see why they called that daylily Minaret! I've never seen that one before. I have some Joe Pyes and love them!

rouge, I used to have Thalictrums years ago. There's a pale yellow one that started out on the ground, I think! never did stake it! Had a 'Hewitt's Double'--lovely thing--that didn't need staking but it died out. I used to stand and stare at it! I have Campanula lactiflora 'Loddon Anna' that I prop up with branches I've cut off trees and shrubs earlier. Love that plant!
Never have to stake Joe Pye 'Chocolate' and 'Gateway' but I have an un-named one (lost tag!) that sort of bows out sideways then starts growing upright again, the Spring foliage on it is gorgeous--been going to move it for years...

Sunny, I love that Aconitum!

I have a Galega officinalis (thanks Helen Dillon! saw this in a video of her old borders) that got huge but now it needs to be divided and moved to a more sunny spot--pretty lavender colored blooms, great plant!

Holy crap, Al, is that photo-shopped? LOL Looks like a Melianthus on steroids!

Campanula, your selections sound awesome!

:note to self: Must seek out and purchase Thalictrum 'Splendide"...

Rouge, I was going to mention that I've been reading about cutting back certain plants early so they don't get so tall is that what's meant by Chelsea chop? Love that term! I'm usually to chicken to try something like that but I might only on the floppy ones ...

Thanks everyone!

My tallest perennials:

Agastache Tutti Fruitti. - over 5' tall
Agastache Blue Haze - over 5' tall
Dahlia Mystic Spirit series - 6' tall (many stunning deep red single flowers)

Perennial grass:
Panicum Heavy Metal - over 5.5' tall

catkin,

I googled "Chelsea Chop". Tons of fun info. It relates to the time of year to do it for many plants, based on the time of the Chelsea Flower Show.

All you folks have me so beat with all your fab plants. I too will be looking up a lot of them.

I second Rouge21's comment - tall and no staking (I'm sick of plants that are SHORT and need to be staked....ERG!)
I have Missouri Ironweed/Vernonia. Second year and its fast approaching 5ft. I love the way the leaves look when its emerging from the ground and growing up to its size. They look like little ruffled knives.
Zebra Hollyhocks got around 7ft last year (I have plenty of seeds if you want any - just email). Unfortunately Lil Bunny &^%$%^*# ate them all when they were seedlings this year (I'm a broken record, I know).
I also have valerian... its beautiful, wispy and smells like a combo of lilacs and apples to me. However, if it rains 3 counties over or there's a strong breeze in another zipcode this thing is FLOP CITY!

A friend has zebra grass (not sure on its botanical name) and its HUGE. Down side is now its very wide and needs to be dividing... probably by way of a Bobcat bulldozer at this point.

Helianthus Augustiflorus (sp?) Swamp Sunflowers

Easily over 10ft if you don't cut them back in late spring.

Bonus - they are one of the last to flower (October) and put on quite a display!

My tallest is heliopsis summer sun (false sun flower) it is the main attraction in my full sun bed. I do put a cage around it but only because i'm picky like that. there is one down the street that does just fine without staking. I have had it for 3 years and haven't noticed re-seeding. It has been blooming for a week here in zone 5. I also have a hibiscus that reaches 7+ feet. I try to keep it back to get it to bush out but it doesn't seem to help. It amazes me every year. It doesn't show life until mid June, grows 7 ft and flowers by the end of July. . . crazy busy plant.

Had a 'Hewitt's Double'--lovely thing--that didn't need staking but it died out. I used to stand and stare at it!

'catkin' I also have HD and it is nice but wait till you see a Splendide in full bloom. It is incredible. See the link below for pictures from last year.

Here is a link that might be useful: Splendide in full sun

This post was edited by rouge21 on Thu, Jul 10, 14 at 8:06

Joe-Pye-Weed
Rudbeckia 'Herbstonne' (not floppy for me- but my soil isn't rich)
Chamerion/Epilobium angustifolium
Thalictrum pubescens. T. rochebrunianum dwindled on me over the years- this guy is more reliable.
Actaea simplex 'Atropurpurea Group'- it is about five or six feet tall as of right now.
Levisticum officinale (Lovage)
Valeriana officinalis (Valerian). I'm in love with the Valerian. It got 4 1/2 -5 feet tall this year. Dark green ferny foliage and masses of airy cream flowers that bloomed a surprisingly long time. The scent was a bit overpowering up-close, but on the breeze it was a lovely musky-vanilla.

I'm also looking forward o seeing my Inula helenium bloom (next year likely). I snagged some seed from a park a couple years ago. Fabulous broad leaves and spidery yellow petals. Theirs must have been six feet or so.

Ps. my 'Spark's Variety' Aconitum has become much more compact in full sun. It was a stretcher and a leaner in the part shade location it was previously in.
CMK

'Valeriana officinalis (Valerian). I'm in love with the Valerian'.
Absolutely! Me too. I only discovered this (growing wild by the Yare river) and was besotted immediately. I have been hovering over the clump, anxiously waiting for seeds (although am hedging my bets and have sown a packet of seeds as well).
And chamerion too - although a couple of pink willowherbs are growing all over the meadow-s I have sowed the white (and supposedly more mannerly - but what do I care?)
My allotment neighbour has a whopping great clump of levisticum which prompted me to rush out and order (another) umbellifer - ferulago sylvestris.....I can never have enough of these tall floaty things and for once, they are utterly in keeping with the location

-campanula, I have seriously been thinking about starting more Valerian for somewhere in the backyard. Wonderful plant! Makes me wonder why people don't use perennial herbs ornamentally in the landscape.

Do you find Lovage yellows/dies back a bit after blooming? That is the only qualm I have with this guy.

Sweet Cicely (Myrrhis odorata) is another lovely one. If I didn't dislike the scent of it so much (local public garden has/had it) I would definitely plant one of those too!
CMK

Echo, thanks for the recs--I have no Agastaches..and I don't know why! Must check them out. I don't think I've seen them in bloom. And I love Dahlias especially the black leaved ones. I have Heavy Metal ready to go into the ground! Just not sure where yet--perhaps next to the 'Rose Glow' Berberis! I have several Miscanthus that DH and I have to cut down with a chainsaw in the Fall (or else they shed/blow everywhere) so I've shied away from more giant grasses--they're creeping back in, though...they add so much and are so graceful!

Rosie,hang in there good things take time! Thanks for the Chelsea Chop scoop!

Thanks for weighing in, David, the Iron Weed sounds great! I have Zebrinus but it seems to have lost its stripes--it is still so pretty! I used to have the red Valerian but I let is seed everywhere then cursed the plant! They must have a taproot, had to dig them out--yikes! Same for Dame's Rocket--Hesperis matronalis. Been digging out babies for for or five years now, which is why I asked if any of people's faves reseeded everywhere. I have gravel nearby that is a perfect germination area! Trying hard to learn my lesson! Hollyhocks are on my list!

Babera, that Hibiscus sounds awesome! I've had a 'Buebird' in the ground for years that has never bloomed or grown much...I know I should move it but haven't gotten around to it....bad me! It probably is too shaded, maybe.

ROUGE!!!!!!!!!! Be still my heart! I love 'Splendide'!!! Those pics did me in! I believe I prefer yours to the one on the link, however. Looks great with your PeeGee!

Allen, that Helianthus looks like a cheery force to be reckoned with--what a beauty! I'm just now in my gardening life beginning to warm up to yellow flowers. I've normally only searched out creams and very pale yellows--I've been livin' on the edge, now, got some Rudbeckias, etc.! Thanks for sharing.

Christin, I'm on the other side of the mountains and the fireweed grows wild around here! Pretty!
Is your Actaea in sun? I plunked mine in shade and would love to try it in the sun--can barely see it now and it is so gorgeous!
I have lovage--same plant for years--do you eat it? Very architectural, fer sure--and yes, I think it may just want to be cut back to the ground after it blooms--then it'll send up a fresh new stalk of celery!
I have Myrrhis that does great in my deep shade--I love lacy texture and the licorice scent, though. Is yours in the sun?

I need to try more stuff in opposite locations than what the tags say...

Campanula, if that Valerian's happy, it may reward you with many babies!

Umbellifers scare me! Lots of natives here that have taken over the roadsides...

Thanks, all!

-catkin, howdy there neighbor ;-)

My Actaea is in a part sun location in an area that doesn't dry out. Tried one in full sun once and it burnt to a crisp, lol. I've got a theory that it handles full sun better in regions that aren't so dry/arid.

Thanks for the info on the Lovage. I'm going to cut it back as soon as it has set seed then. Nah...I don't eat it. Kind of smells/tastes of musty old celery to me, lol. Do you use it for culinary purposes? Bloody Mary straws? ;-D

Don't have the Myrrhis personally, but saw it in a local public garden. Theirs was in full sun. That is neat yours does deep shade...a versatile plant if it can do such polar opposites with sun exposure!

Sounds like you have a lot of neat plants in your garden...I'd love to see pics someday (hint, hint ;-)
CMK

Thalactrium rochebrunianum, holy cow! Year one it was at least 8' I cant wait til it blooms this year. i thought my cimifuga was tall...no comparison.

Catkin, I discovered Agastaches only a couple of years ago and I wouldn't have a garden without them. They have a lot of virtues:
Three to four months of flowers
Very appealing scented foliage and flowers
Bee and butterfly magnets ( and hummers like them too)
Lots of variety in flower color
They don't need staking, though I don't know what happens to them in a very heavy rain ( don't have summer rain in my climate )
This year I actually had the bonus of three seedlings.
The only downside I've ever heard is that they dislike heavy wet soils in winter and may die off in those situations, but I have heavy soil and mine have survived so far.

Here is a small video showing this particular Thalictrum. (I am assuming that the particular specimen shown in not yet in full bloom)

Here is a link that might be useful: Thalictrum Rochebrunianum

Although it is actually a shrub, in my part of the country Black Knight Butterfly Bush grows as a woody perennial. It is my tallest "perennial." Second runner-up would be my Russian Sage.

Christin, good to know I can move the Cimicifuga if I need to! I just nibble on a lovage leaf if I'm working nearby!

I'm definitely moving some Sweet Cicely next Spring!

Posting pics online is on my to do list--unfortunately I need hands on learning--so it may take a while!

Unbidden, those meadow rues are gorgeous!

Echo, I have lots of wet soil most of the year but am working on lightening it up, so maybe an Agastache is in my future! Thanks for all the specs!

Rouge, thanks for sharing that!

Plantingman, DH won't let me plant Buddleias--they seeded all over the place--especially in our gravel driveway...I'll check out the Russian Sage.

I'm pretty sure I've lost a lot of plants to poor drainage.

Thanks for weighing in everyone!