Q. My Itoh peonies seem to produce fewer buds and leaves every year. What can I do for them?
Itoh, or intersectional, peonies are a cross between herbaceous and tree peonies. These hybrids (named in honor of hybridizer Toichi Itoh) thrive in the same conditions as herbaceous peonies. They are best grown in a field or garden, although pots may be used for young plants (2-3 years). Tissue-cultured peonies require 2-3 years to reach blooming size. Itoh peonies are vigorous; it is important to leave them enough room to grow.
One possible cause of peonies' failure to thrive is locating them too close to a tree, where they have to compete with the tree roots for nutrients and water. Another possible cause is cutting too many flowers. When cutting peony flowers it is practically impossible not to also cut leaves, which the plant needs for creating food reserves. Cut flowers sparingly, leaving as much foliage as possible. A rule of thumb is not to cut flowers from plants less than three years old and to leave a mature plant with about 50 percent of its flowers. Also, do not cut the plants down immediately after flowering--that prevents necessary buildup of food reserves. Wait until fall frost, then cut back your Itohs to 1 inch and dispose of the cut foliage.
General care instructions:
- Location: All peonies do well in full sun, although flowers may last longer in partial shade.
- Planting: If peonies are received in pots, plant them to the same depth that they were in the pots. If received bare-root, plant as soon as possible. To ensure sufficient hydration, first soak roots in cool water for 15-20 minutes. Proper planting depth is with the uppermost bud 1 inch below soil level. A hole larger than the pot or roots should be prepared with compost mixed in 1 foot deep. A 3-foot space should be left between plants.
- Soil: The soil must be well-draining. Poor drainage can lead to botrytis, a fungal disease that attacks stems and roots.
- Fertilizer: Apply fish and seaweed emulsion by the gallon, both as a foliar spray when leaves are emerging and as a root drench when planting and during fall cleanup. Other fertilizer options are well-decomposed compost, bone meal (be wary if you have digging dogs or raccoons), Bulb-tone®, or rock dust. When applying compost be careful not lay down too thick a layer, as this could increase the planting depth and thus reduce blooming. The best way to apply compost is to mix it in a ring around the peony.
- Dormancy and winter protection: To avoid disease carryover, stems should be cut down in fall and destroyed. Most buds of Itoh varieties are found on the crown just under the soil as for herbaceous peonies. However, some buds may be found on the lower parts of the stems. These are not necessary for growth and may be cut or left on the plant. Although Itoh peonies are very winter-hardy, mulching is recommended for young plants in areas of little snowfall. Mulch should be removed in spring to allow new shoots to emerge.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service