Vernonia species

I would like some information on the following Vernonia species:

- Vernonia angustifolia x missurica [missourica?]

- Vernonia glauca

I've looked on the net but there is little information the be found on these plants and the information that I found is often contradictory.
Are these species invasive? What is their height (in normal garden circumstances)? Do they flower reliable? Do they need staking?

I would like to grow one of these species in my Dutch garden as a replacement for Eupatorium maculatum 'Atropurpureum' which does need a lot of water in the growing season and needs staking.

All information is appreciated. Thanks in advance.

 

Shouldn't be too difficult to find information on Vernonia glauca, as it is a species native to the US (Flora of North America: Vernonia).

As for the hybrid cross, is it something introduced by only a few (or one) nurseries?

More general information re: Vernonia species cultivation can be read by viewing Armitage's book on perennials (via Amazon). Click on Search Inside This Book -> Vernonia -> page 1078 / 1079

 

The information I found on Vernonia glauca was contradictory, especially about its height and invasiveness. Some sources say this species can reach 7 feet others (mainly commercial growers) say it grows to 3 or 4 feet. The same contradictory information was found on its invasiveness.

The hybrid cross Vernonia angustifolia x missurica was, according to my information, made by Woodlanders Nursery in the USA. However this plant is at the moment not offered by Woodlanderd Nursery nor is it mentioned in their website catalogue.
On the web their is little information to be found on this cross.

The well known Dutch nursery Hessenhof (www.hessenhof.nl) offers different forms of this hybrid cross: a high form of 7 feet and a low form of 5 feet. Both forms are slow growers. Because of its slow growth Hessenhof also offers seedlings of this cross hybrid. The seedlings eventually make large plants of about 7 foot.