For the second year in a row one of my tree peonies has had lots of buds but they don’t open. Is there an explanation.
Also when is the best time to prune tree peonies and how.
Thank you for contacting the Toronto Master Gardeners regardeing your tree peonies.
Tree peonies grow best in neutral, humus-rich, well-drained soils. They prefer a full sun (6+ hts.) or light-shaded location. These plants are hardy in our zone, but the foliage and flower buds can be damaged by late frosts, as a result they should be planted in a sheltered position to prevent damage to floral buds by strong winds. From your photo it appears as if your flower buds could have been damaged by fthe reeze thaw cycles that we have experienced the last two winters.
Tree peonies also benefit from some fertilizer. Fertilize a tree peony the same way you do for its herbaceous counterpart. They are very responsive to feeding, but care should be taken not to over-fertilize. Use a complete fertilizer such as 5-10-5, referred to as a complete fertilizer because it contains a beneficial percentage of nitrogen, phosphorous, and potassium to promote growth flower production and root growth. Make sure to follow directions on the label.
Spring is best time to prune your tree peony. Use appropriate sized by-pass pruner or lopper which are disinfected after each cut to prevent potential spread of disease. Pruning should be done just above an outward facing bud. Remove spent blooms after flowering. Careful shaping of a leggy plant is done in the spring and gradually over several years. This may result in a loss of a few of the year’s flowers. While pruning will stimulate growth, peonies do grow slowly. There is an excellent article on Garden Making magazine: How to prune Japanese tree peonies
Good Luck with your tree peony.