When I first started gardening (eons ago, it seems) in my tiny Toronto backyard, one of the first flowers I bought was a Black Eyed Susan. It was lovely – small, hairy leaves with bright orange-yellow flowers in late summer. I planted it in an area that started out in full sun but gradually, as surrounding trees grew, became shady, which is when I transplanted a chunk of it to the County. Turns out this was Rudbeckia fulgida var. sullivantii ‘Goldsturm.’ I didn’t know the Latin name then, and didn’t know how many Rudbeckia species were out there and available.
Turns out there are a lot! At least 25 accepted species with a lot of different common names that can be confusing – one of the reasons I like to use botanical (Latin) names as much as possible.
In my garden they start blooming in earnest the second week of August and will continue until mid September, longer if dead-headed. The different species have different ways of spreading — R. hirta and R. fulgida will quickly spread by underground runners as well as self-seeding.
My favourite tall Rudbeckia (one of my favourite perennials in general) is Rudbeckia laciniata. I’ve read where it likes moist areas, stream beds and such, but I find that they send their seeds everywhere and will grow everywhere, even in the driest areas of the yard. They can grow to five or six feet tall but the neat thing is you can, in early summer, clip them back by half or more (as you may do with Asters and Solidago – Goldenrod) so that you keep a clump bushy and shorter.