My mother used to say, “too much is too much, too little is too little, and enough is enough!”. Unless you’re on a dirt road, driving through endless farm fields, brimming with sunflowers, there can never be too little yellow flowers in the garden, because, in my opinion, a little yellow goes a long way.

 

With this in mind, I planted a single orange coneflower (Rudbeckia fulgida var. umbrosa) in my petite front garden last year. I thought it would be enough, but, to my surprise, it grew tenfold and produced a lot of yellow flowers. I should have known better, as this variety spreads quickly. It loved my garden soil, too much.

 

Now the plan is to dig it out when it’s done blooming, and find it a new home with more elbow room, perhaps by the long side fence where it can co-exist happily with another robust plant, rose turtlehead (Chelone obliqua). In small spaces, large aggressive plants take up too much valuable space, where diversity is desirable. This variety of black-eyed Susan (var. umbrosa) is best used in larger gardens, especially rain gardens and pond edges, because it also tolerates temporary flooding. Showy coneflower (R. fulgida var

sullivantii) is similar but more clump-forming and likes dry, well-drained soil.

 

In its place, I’ll plant black-eyed Susan (R. hirta) and its bloom companion, butterfly milkweed (Asclepias tuberosa). Both are lesser in size, clump-forming and with a slower rate of growth. Keep in mind that black-eyed Susan is a short-lived perennial or biennial (lives two years) that seeds around, so I’ll mulch or pull seedlings when they appear. Reddish and burgundy color variations (often called gloriosa daisy) occur in Missouri prairies and are worth growing in the garden. Edgar Denison, author of Missouri Wildflowers, used to grow gloriosa daisies in his Kirkwood garden.

 

I am surprised to see Missouri coneflower (R. missouriensis) being used so much in garden designs. It is another short-lived perennial (or biennial) that is well-suited to rock gardens and gravel sidewalks and driveways. If you’ve ever seen it growing in a rocky glade, you would understand how little soil it tolerates and prefers. It performs similarly to rose verbena (Glandularia canadensis) and pale purple coneflower (Echinacea pallida). All are short-lived in regular clay garden soil, where they tend to flop and die. They’re longer lived in well-drained, rocky soil or limestone gravel, like at the edge of a retaining wall.

 

The most long-lived and robust rudbeckia is sweet coneflower (R. subtomentosa), a 3-4 foot tall clump-forming prairie plant. It grows densely and tall in full-sun gardens, and combines well with switchgrass (Panicum virgatum) or little bluestem (Schizachyrium scoparium) in large-scale spaces. It also tolerates part shade, though it is slightly shorter and thinner in open woodlands. In this situation, it combines well with river oats ( Chasmanthium latifolium), late purple aster (Symphyotrichum patens)and rough-leaved goldenrod (Solidago rugosa). Wherever it grows, its flowers stand tall on sturdy stems. The cultivar ‘Henry Eilers’ originates from Madison County, Illinois, not far from St. Louis. In this regard, it is a local ecotype native plant, worth considering for its unique tube-shaped petals. This is a robust perennial, ideally used in larger gardens.

 

There is a black-eyed Susan that grows in the woods, though it’s typically only used in large-scale gardens, and woodland restorations in floodplains.

Goldenglow (R. laciniata) spreads aggressively and can reach 7-8 feet in height or more. The leafy greens are eaten steamed in spring, but not too much, it is a mild laxative. For homeowners who back up to a shady creek, this one is a good choice to help stabilize the bank. Plant it with garden phlox ( Phlox paniculata), tall yellow wingstem (Verbesina alternifolia) and globe sedge (Carex grayii) to stabilize vulnerable shady creek banks.

 

Black-eyed Susan was perhaps first named in a 1720 British ballad by John Gay, describing a tearful woman, black-eyed Susan, separated from her love by high seas and war. It reads…