I can't help you with this and this is an incredibly underused board but there are lots of good regional guides to visiting gardens that you can find in bookstores-- I have "the complete guide to north american gardens" although I only have the northeast book. It is certainly not complete but it is a good guide nonetheless.

I live and work in the corridor you plan to travel. Louisville will be on your flight path, along I-65.

Bernheim Arboretum and Research Forest is a fine stop, just a mile off I-65 in Clermont KY north of Elizabethtown. In existence since the 1930s, it evolved into a fine arboretum under the loving hand of horticulturist Buddy Hubbuch starting in the 1960s and its woody collection is probably one of the finest in the Ohio River valley region. Visit their website at www.bernheim.org and learn about their expanded emphasis on their natural areas mission, updated master planning, and "green architecture" for the new visitor's center.

Continuing north into Louisville, I'll put in a plug for Louisville Metro Parks (that's where I work) that are an easy hop off the highway. The historic core of the system was designed by Frederick Law Olmsted in the 1890s, linked by broad tree-lined neighborhood parkways, and we're proud to say that we are actively restoring and rehabiliting the design intent of this wonderful legacy. From the limestone ridges and Beargrass Creek valley landscape of Cherokee Park; to the wild scenic reservation of Iroquois Park's forests; to the broad vistas of the Ohio River valley in Shawnee Park, the Louisville Metro Parks offers something of interest for all and a respite from your hectic trip north. Sound like a chamber of commerce ad? There is also the relatively new Waterfront Park downtown on the river (not a Metro Park, but we are proud of it too) with ample brand new playground installations and huge waterplay areas for cooling down on what promises to be a hot Memorial Day weekend.

Also in the city is Cave Hill Cemetery, established in 1848. Not exactly what you'd term a public garden, but it contains the oldest collection of woody plants in Louisville and is a calming green space in the middle of Louisville's urban center. The architecture of the memorials is complemented by the plants, and is worth the visit.

Finally, I'd recommend a visit to Yew Dell Gardens in Crestwood KY, just 20 minutes up I-71 from Louisville. The estate of the late Theodore Klein, well-known midwest nurseryman, is a fabulous collection of plants assembled over the last 70 years and now under the guidance of horticulturist Paul Cappiello and the non-profit governing board. Mr. Klein was an avid plantsman with a keen eye for the extraordinary among the ordinary, especially in regard to native plants of the region. He was incredibly active in the holly and magnolia realms, and the plantings around his property illustrate that better than any words could. See their website at www.yewdellgardens.org for more info.

Enjoy your time passing through our region, and I hope you like some of these suggestions.

Not really a public garden... when I was in MI .. there is a school -- Cranbrook... it is a wonderful place to wander around.. lots of artwork in the gardens.. waterfalls.. and great spots to think and maybe a picnic on the greens..
I love the place... still have a gate photo on my wall... you would enjoy it I believe...
have fun on the trip