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.