Tree Peonies are among the garden aristocrats, ranking with azaleas, magnolias, flowering cherries, and wistarias. During their blooming period in May and June, no plants can surpass them.
The comparatively few hardy plants which produce flowers of comparable size are scarcely in the same class as these Oriental shrubs of unique delicacy and charm.
Most garden peonies are herbaceous. Therefore, these are the kinds usually called to mind when peonies are mentioned.
Paeonia × Suffruticosa
There are a few woody species native to China, however, and of these, the best known is the mountain (Paeonia × suffruticosa)
The height of these shrubs is between 4’ and 5’ feet, although vigorous forms have surpassed ten feet, according to the records.
One may conclude that the name came to be applied because of the upright and self-supporting branches, often arising from a short picturesque, rough-barked trunk, which may suggest a venerable tree.
Cultivating Tree Peonies In Early Times
Tree peonies (or bo-tan) have been cultivated since very early times in China and Japan. However, they were first made known to Western gardeners through the generosity of Sir Joseph Banks, the famous eighteenth-century patron of botany and horticulture in England.
Inspired by Chinese drawings of the lovely flowers, Sir Joseph retained a Mr. Duncan, medical attache of the East India Company at Canton, whose task was to obtain a living plant for Kew Gardens, which had been founded in London nearly thirty years before.
The efforts of this Mr. Duncan were successful, and one of the Indiamen came back in 1787 with the double, pale pink, purplish-centered tree peony, which the contemporary botanist Andrews named variety Banksy.
This original plant grew at Kew Gardens for over 50 years but finally had to be removed for construction work.
Banks Peony
Some plants in this country have probably surpassed this age. Today, Banks peony appears somewhat blowsy when compared with the delicate single and semi-double varieties, but it was a treasure in its time.
Dignified old bushes 3’ or 4’ feet high may still be seen, often in quiet old dooryards in the Eastern states.
Tree Peonies’ Features
Tree peonies have thickish, pinnately compound leaves from 10” to 18” inches long, which resemble those of herbaceous peonies.
Leaves, new growth, and flowers are all produced early in the growing season. This rapid development in May and June contributes to the breathtaking quality of the shrubs.
Later in the season, there is extensive root growth, but no development above ground except maturing and ripening of the characteristic fruit follicles.
These ripe follicles add little to the garden picture (unless a trial lot is to be raised from seed) and only use up reserves of food that should be retained for bloom the following spring.
Propagation Methods
Tree peonies are usually propagated by grafting the choice varieties on divisions of the thick tuberous roots of herbaceous peonies.
This combination makes more vigorous plants than one would imagine, and under good growing conditions, the top often forms roots.
Practice Layering
Layering is also often practiced but is rather slow for large-scale production. Nevertheless, several amateurs and professionals raise tree peonies from seeds, and the impressive plantings at Highland Park in Rochester, New York, attest to the fine results that can be obtained in this way.
Whether tree peonies are on their own or their “cousin’s” roots, growth requirements are practically the same, and a garden in which herbaceous peonies thrive will be equally favorable for mountains.
Best Soil Conditions For Planting
A deep fertile soil near the neutral point or slightly alkaline is best, and its precise type should make little difference so long as it is porous and well-drained.
Sandy or light soils are satisfactory if generously enriched, and also heavy types if opened up with compost and manure. Heavy soils produce somewhat better bloom, but these, in particular, require deep preparation.
This does not mean turning over to a shovel’s depth, but trenching a full 3’ feet is the best gardening tradition.
Plant Peonies In Early Autumn
Early autumn is the best time to plant all peonies, as vigorous root growth takes place in the weeks before cold weather sets in.
However, rather than postpone planting the shrubby kinds and run the danger of missing them, gardeners can also plant them in late March or in April —the sooner, the better.
New plantings should be watered if the ground gets dry during the first summer, but if the beds have been well prepared, the roots will soon become established, and further watering is rarely necessary.
Regular Trenching
Tree peonies thrive in full sunlight or considerable shade, but they are invariably damaged when there is root competition with trees.
If they cannot be planted a safe distance from trees, regular trenching every three or four years or some kind of barrier beneath the surface should be arranged to keep tree roots out of the area.
Botrytis And Troubles Of Herbaceous Peonies
Botrytis and other troubles of herbaceous peonies sometimes infect the mountains but to a less troublesome or negligible degree. This is because their harder tissues are less open to injury.
Even so, it is a good policy to collect the leaves from the plants in the autumn and to be sure they are placed on the pile for burning or are buried. Leaving the fallen leaves for mulch is not advisable.
Elegance Tree Peony Uses
The elegance and refinement of tree peonies nearly prescribe their use in formal and sophisticated parts of the garden. In a garden of symmetrical pattern, tree peonies are fine for accent in balanced positions.
They can be featured around a central birdbath, sundial, or possibly on either side of the walk where one enters the garden.
The plants should be placed about 4’ feet from the edge of a walk, so the flowers can be admired at close range.
Most Desirable Shrubs
Tree peonies are so lovely that one has to draw largely on superlatives in speaking of them. For all practical purposes, the varieties of mountains and the newer hybrids with traits of golden peony (Paeonia lutea) can be placed in the same category; they are among our most desirable shrubs.
The price of one or two of them may be just the amount kept in mind for a birthday gift or other present.
I suggest selecting from the description now and next May to visit collections at nurseries or gardens to make notes for further acquisitions. One of the outstanding collections may be seen at Swarthmore College in Pennsylvania.
44659 by Ben Blackburn