How tall do you want your plant to be then? Two that spring to mind are Joe Pye Weed and Hollyhocks as far as tall goes. However I don't believe that Joe Pye blooms until later in the season and my hollyhocks are blooming now. My hollyhocks are flopping like nobody's business also but if they weren't they would be around 6' tall.

Hope this helps.

Kate

I suggest Helianthus Maximilian (Perennial Sunflower). It grows very tall and blooms for a long time.

Carol

If you don't mind a few ornamental grasses instead of all blooming perennials, there are some gorgeous, tall (but not too wide) varieties that would mix with perennials. I don't know what works in your zone to make a recommendation of a specific grass. In my garden, I love miscanthus 'Cosmopolitan'. The green/white stripe variegation is a great background for purple, blue, red, orange blooms.

Tall grass does look nice for a long time. Some perennials look ratty after they bloom.

Carol and I are on a similar wavelength only I have had years of experience with the Autumn sunflower, Helianthus Angustifolia. Paired with late blooming Asters, mums and grasses it makes quite a nice display in late fall.

I love my Helianthus for its height and long, abundant bloom time but I had to move mine out of a bed with similar width partly because spread too much by seed and got too wide for the space.
I have a darker yellow Echinacea which is much narrower and more well behaved. It also blooms for a long period. This year it has gotten very tall and doesn't need staking.

I think the zone might be a little iffy but Leycesteria formosa is a tall narrow shrub that is attractive all year long. Nice foliage, interesting flowers/berries in summer, in the winter after it sheds it's leaves looks like a clump of sea green bamboo, some say it's hardy to zone 6 others say zone 7. It doesn't spread like bamboo, stays quite manageable. Also another vote for ornamental grasses for year round interest.

Here is a link that might be useful: Leycesteria formosa

The tallest perennials in my garden are:

Bugbane (between 6-7 ft.tall)...blooms from July to Sep.

Queen of the Prairie (about 6 ft. tall)...blooms July to Aug.

Butterfly weed (a tad over 5 ft. tall)...blooms all summer if you deadhead.

Giant hyssop (4-5 ft. tall)...blooms July through Aug. Will produce new flush if deadheaded.

All 4 of these plants grow well in my zone (6a) without winter protection.

my favorite tall plant is Rudbeckia Herbstone ( think it is also called August Sun). 7 feet tall and completely self supporting. Becomes a pleasant clump but does not spread. Beautiful bright yellow daisies from late July till November.

A tall grass has the advantage of giving some privacy in the winter. You cut them back after they start growth in the spring and it takes quite a while for them to get tall again in the summer but it might be interesting to use some grasses for winter along with things like the Herbstonne that will grow tall more quickly for the summer.

I agree with the above posters on ornamental grasses. However, if I were you, I would also consider some ornamental, and preferably evergreen, shrubs. Shrubs give substance to a border and are what designers call "bones". I know you probably want maximum numbers of plants and flowers, we all do. But, I can tell you that a shrub or five will go a long way toward giving you the impact you're after. Take a good look at shrubs with a long bloom season and/or with colored or variegated foliage.

I fully agree with the above post on Rudbeckia Herbstone. The most gorgeous and tallest perennial I have in my garden. I highly recommend this plant.

Would you consider a buddleia? Also, Miss Huff Lantana may work--emerges late but then blooms until frost. not sure about hardiness in your zone though.

I would nix the all-perennial look in Cincy - you will not have anything there for 5-6 mos out of the yr., and go for shrubs and evergreens - an 8 ft wide border could be very beautiful.
Have you seen the following
Blue Holly - red berries in winter and shiny leaves - try Blue Boy and Blue Girl for evergreen hollies

The deciduous hollies for heavy crops of red berries

Various azaleas and dwarf rhodos like Purple Gem can be tucked up next to larger shrubs for a little shelter or even large rocks- huge spring color in a wide array from white, pink, purple, red, yellow

Pieris - You have Mountain Fire for red foliage, Valley Valentine for hot pink flowers in spring, etc

Variegated Osmanthus and Hollies - there are a number of evergreen variegated shrubs - even the mounding or prostrate Euonymous

Hypericum Albury Purple - burgundy leaves, yellow flowers, red berries - a cornucopia of color

Buddleia - as someone mentioned - a butterfly magnet

The red and yellow twig dogwoods - you would be amazed at how screaming colorful they are in winter

1 Witchhazel for bloom in January - I have Jelena that I put by the driveway and I have a big smile every yr in Jan as I pull in and look at those flowers

lilacs and dwarf lilacs late spring- I am very partial to Donald Wyman which is the nicest lilac I have ever had the flower panicles are just enormous - like a bunch of grapes

An arbor with hardy roses and clematis mixed on it
There are large flowered clems that bloom spring and fall, and the viticellas like John Treasure or Betty Corning that bloom their hearts out all summer long. You can also pair in the Sweet Autumn Clematis with another clem to give a giant send off to summer.

Dwarf Magnolias like Jane-magenta & Butterfly - lt yellow

The dwarf chamaecyparis like nana and nana Aurea

Weigelas

Beauty Berry - Callicarpa

If I had a border like that I would mix in Trumpet, Asiatic, Oriental and Species Lilies Rubra and Alba, and L. Black Beauty which for me is often almost 7 ft tall, and also Dahlias - which will bloom heavily till a hard frost and can some get to 5 ft tall- I have taken my dahlias in during Thanksgiving week before. Also lots of bulbs like crocus, leucojum, narcissus, tulips, alliums, fritillaria, liatris, and all the non-hardy summer blooming bulbs like Acidanthera which smells so heavenly.

Other evergreen shrubs -
Alberta Spruce, hemlock - just prune it, Pencil Holly, Pencil Juniper, Arborvitae - prune them
There is a dwarf white birch that is only 10-12 ft
Also crab apples, dwarf hawthorns, Pink Diamond hydrangea, Pee Gee Hydrangea in tree form. there are dwarf forsythias that stay about 4-5 ft tall

Tall perennials - many have been mentioned but you should take into account that they will take the best part of the summer to achieve their height so you start with them poking out of the ground in May and take it from there.

Just because I'm partial to Monarch butterflies I always plant several varieties of Asclepias which is the only plant they lay eggs on and the caterpillars eat.
I also plant Lobelia Cardinalis - Cardinal Flower and Monarda Jacob Kline which draws maybe 2-3 pairs of hummingbirds to my garden every yr.

The tallest perennials in my garden are all about 4-5 ft Aster Honeysong Pink - 5 ft high and wide, perennial sunflowers Heliopsis and Helianthus, ASter Jindai, Anemone Honorine Jobert, Boltonia

There is so much you could do with that space I hope you post some pics
A

Rudbeckia 'Herbstonne' is also a favorite in my garden - a great, long-blooming anchor perennial. Another good tall Rudbeckia is R. triloba (brown-eyed Susan).

Swamp sunflower (Helianthus angustifolius) is a very nice late summer-fall bloomer, but given its preferred moist soil in a warm climate it can be downright invasive (spreading by runners). Joe-pye weed can also take over, but through seedlings (the straight species seems to be the most prolific self-seeder, at least in my garden).

If you are interested in asters, Tartarian aster will grow a few feet taller than Tartarian Aster Jin Dai.

What about the long blooming dahlias, tall, need staking,
but bloom for months

I'm approximately in your zone and perennials, dahlias and grasses take a while to "grow up." If you want privacy, you should consider a flowering shrub border. Alternate with Rose of Sharon (late summer), Butterfly Bush (mid-summer), smaller lilacs (spring), hydrangeas (summer) etc. Leave some gaps for perennials or summer blooming shrubs like tropical hibiscus, or tall roses, etc. Perennials won't fill the bill for what you want. For instance, while I love dahlias they don't flower around here until late July/August.

WOW - thanks to all for sooo many suggestions. I still have quite a bit of time before I start planting so I will research all the options you've given me and decide on which one Im gonna go with. Im going to go with the majority on this and "nix" the all perennial idea. As you all pointed out, it wont give me all-season privacy (which is what Im looking for).

Thanks Again :-)

jb

There are some Camellias that get quite tall, produce flowers at different times from late fall through early-mid spring and are evergreen. There are a few varieties that will tolerate zone 6.

Here is a Camellia link that has information about growing them in zone 6.

Here is a link that might be useful: Camellias for Zone 6