Butterbur a.k.a. Petasites
These enormous three and a half feet tall plants grow 5 to 6 feet wide, with giant heart-shaped leaves reaching about 1 to 2 feet wide and blooming with delicate spring flowers. It’s also an edible and medicinal big-leaf outdoor plant that grows in partial shade.
But we must mention that they enjoy clay soils that are always moist, surviving in zones 4 to 9. This makes them ideal for bog or rain gardens. Butterburs are beautiful at the edge of a water feature but can be aggressive, so be sure to give it a boundary like a small fence.
Cardoon a.k.a. Cynara Cardunculus
Cardoon is a gorgeous ornamental plant, closely related to the artichoke, that has become rather popular recently.
The basal foliage, which, in mild climates, is around much of the year, is an arching mound of deeply divided and lightly spined, silvery green leaves with a pure white bottom. Individual leaves can reach up to 3 feet long, forming clumps 5 feet across when grown correctly.
Cardoon requires rich, well-drained soil and periodic deep watering during dry weather. At the beginning to midsummer, stout flower stems bear large spiny buds that fan out to thistlelike purple blooms.
We recommend cutting them back immediately after flowering, which will force them to grow new basal foliage, allowing them to thrive into late autumn.
