I am in northern Michigan, zone 5. I have grown 5 of these for 4 years, and I love them. They are more like a small shrub with their woody stems. Mine grow about 3' high with a spread of about 4'. Once they start blooming this beautiful yellow, they will continue into fall with a little deadheading. I have not found them invasive at all, but they do have a fairly wide spread.

I think early spring would be best, but after flowering would be second choice. We got a bunch of them donated for the GNPS sale and I had to whack them back hard. They responded well to that (Feb/Mar). The bark is very nice; this plant needs more exposure in the public. Maybe if I give bobbygil a small one he will upgrade my sandwich to a combo.

Ginseng: Seeds need to be stratified. After collecting the fruit in autumn, dig a hole in a well-drained, shady area about 30cm deep and 1 metre wide. Line the sides and bottom with rocks or bricks. Line the bottom with 2cm sand, then 2cm of seeds, then another layer of sand. Repeat layers as required, ending with sand, and cover the whole with a sheet of plywood. Leave for up to 18 months, but at least 90 days, keeping them cold and moist. Plant seeds or roots in autumn or winter. Plant them about 5-10mm deep, and cover with leaf mulch about 2cm thick. Do not allow the seeds to dry out. Germination may take a year or more. Plant produces seed when the plant has grown 2 prongs (or leaves), at about 3-4 years. The plant will add a third prong when 5-9 years old. Grows best in cool, shaded hardwood forests. The plant lies dormant for some years and does not grow new tops every year. One-year-old plants have 3 leaflets, resembling a strawberry plant. In the second year it usually has 5 leaflets, and in the following years it begins to branch out with 2, 3 or 4 prongs with 3-5 leaflets in each prong. Prefers a soil with pH 5.0-6.5. St. John's Wort: Propagate by seed sown in spring in a sandy medium, runners in autumn, softwood cuttings in late spring or early summer, or division in spring. Ideal temperature for seeds is 20C, and germination is slow. Seeds should be just barely covered. They are slow and irregular to germination and may take from 30-90 days. Water seeds once or twice a day until they germinate, then transplant to the garden. Will grow in most well-drained soils and full sun or dappled shade. Succeeds in dry soils. It is a short-lived plant, although it can grow rapidly, and should be replaced every 5-6 years. Rarely needs pruning, but deadwood should be removed in spring if necessary. NB. St. John's Wort is a declared noxious weeds in many areas. Check with your local authorities to see if you aren't breaking any laws by growing it.

Kalm's St John's Wort is native to the Midwest. I absolutely love this plant, but unfortunately it is not native to your neck of the woods. K-SJW is completely maintenance free and has beautiful yellow mid-summer flowers which the bees love. It is a small dense shrub with a nice tight globe form, maturing to about 3 feet tall and wide. It looks especially nice when massed. New Jersey Tea is also nice. NJT grows to about 2.5 feet tall and wide. It gets interesting white flowers in early summer. It is a favorite for browsing by rabbit and deer so just keep that in mind with placement. No maintenance other than to trim out winter dieback which may not be an issue where you live. Blue False Indigo, a herbaceous perennial, is very shrub-like in appearance. Annual cutting back of dead stems in spring would be all that's required Consider planting Prairie Dropseed, a native grass to your area. Plant PDS 24 inches on center in rows or massed. It's a beautiful native with excellent form. It's not likely to reseed and is a well-behaved clump former. PDS has a soft fine texture and a fun popcorn aroma when in flower. No maintenance except removal of last year's growth in spring.