Almost everyone can identify traditional garden plant favorites such as the bearded iris and herbaceous peony. But, when such common plants remain blithely bloomless or produce the wrong flowers, new gardeners may despair of ever being able to grow anything.
If those classic beauties seem to you to be as finicky as they are famed, just keep in mind that some of these plants prefer to be shallow planted.
Take showy bearded irises such as ‘Beverly Sills’ and ‘Immortality,’ for example. Keep in mind that you don’t want to plant iris rhizomes as deeply as you would plant lily or tulip bulbs.
Instead, those rhizomes should be placed so that they lie horizontally almost on top of the ground. Envision them as logs which are floating down a river. The lower part of each log should lie below the surface of the water—in this case, the surface of the ground—and the upper part remain visible barely above that surface.
Since it can be difficult to keep iris “logs” in place under those circumstances, you might want to use the large “staples” recommended for landscape fabric to pin down your rhizomes as well, until they get their roots well established. Don’t mulch those plants and don’t allow them to become so shaded or weedy that the sun doesn’t reach the tops of their rhizomes, or they may rot and/or fail to bloom. (These recommendations apply only to bearded irises; other types have their own eccentricities!)
Herbaceous peonies, such as the old favorites ‘Monsieur Jules Elie’ and ‘Festiva Maxima,’ also should be planted shallowly. If you purchase a potted one which already is blooming, you simply can set it at the same depth that it grew in its container. When planting bareroot herbaceous peonies, however, be careful that you cover their eyes (growing points) with no more than 2 inches of soil in the north, only 1 inch in the south.
This can be more difficult than it sounds since not all of those points, which resemble little pink or white buds, will lie on the same plane. So make sure that the lowest one is no deeper than 2 inches below the ground. If you mulch your peonies over winter, pull that mulch off of their crowns in the spring to prevent your plants from getting in too deep.
Keep in mind also that peonies and irises often won’t bloom the year after they are planted or divided. Their “needing time” doesn’t mean they don’t like you, simply that they must put down roots before they think about performing again.
As it turns out, gardening wisdom isn’t always all that deep. In fact, sometimes it barely scratches the surface!