This is the second installment on this popular topic. Click here to read about Turtlehead, Coreopsis, Spiderwort and Baptisia.
There are about 150 different Goldenrods, most of them native to the prairies, river banks, and mountains of North America. They’ve also spread widely throughout Europe, especially along roadsides and in vacant lots. They’re good for a brief back-of-the-border splash of gold in mid or late summer, though hybrids are now available in short or medium heights and with longer flowering periods. Not as allergy-provoking as is commonly believed.
Newer hybrids especially make excellent, long-lasting cut flowers, especially in mixed arrangements. They dry well, too.
Goldenrods grow to 5′ or more tall, though some newer varieties are shorter. They clump or spread by rhizomes, are best in full sun, are super-hardy (to Zone 2), and can flower from July to October (the hybrids having the longest bloom period).
Goldenrods are quite drought-tolerant. They not only don't need fertilization but do better without it - it can produce excessive growth that causes the stems to flop. Foliage can be affected by mildew, which is best “treated” by siting the plants at the back of the border where the foliage won’t show. Division every 3-4 years will help maintain plant vigor and blooms, while reducing mildew infestation. The taller variety has a better form if it's cut back by half in early June.
Heleopsis/False Sunflower, or Ox-eye Sunflower
Here's another native perennial with a long bloom period - from June to August. Depending on the variety, it grows to 3 to 6 feet tall and 2 to 4 feet wide. Best in full sun, it also tolerates some shade. Hardy down to Zone 3 (way colder than Maryland), it also tolerates poor soil. One tough plant.
Care. Heleopsis is quite drought-tolerant and is bothered by no serious pests. To extend its season of bloom, just deadhead the spent flowers.
Rudbeckia is Maryland's State Flower and probably the best known native perennial in our region. Shown here is the popular variety ‘Goldstrum,’ which was voted the Perennial of the Year in 1999. The species is native to the Southern and Eastern U.S. Rudbeckias have a long bloom time, from July into September, and do best in full sun or light shade. They spread freely by seedling and are hardy down to Zone 3.
Care. They're fairly drought-tolerant, once established. (Newly planted, they need to be watched and watered regularly during the first season.) Most gardeners leave the attractive seedheads standing all winter for the birds; others remove the dead flowers to prevent spreading. Pinching in May can produce bushier, shorter plants, though I’ve never done it myself - the 'Goldstrum’ variety is short enough to not need pinching. There's no need to divide them.
For another look entirely, the purple spikes of Liatris really stand out in the garden. It grows to 3 to 4 feet tall and is an insect magnet, attracting Monarch and Swallowtail butterflies in particular.
Planting and Care. Liatris is grown from corms (like bulbs), which should be planted no more than 1 to 2 inches deep (counting any mulch on top of the soil). Stringy roots indicate which side is the bottom. Don't plant them too deeply, or in waterlogged areas. Liatris is very drought-tolerant.