Tree peonies are usually sold only in spring. “I don't understand why,” says John, who recommends planting them in mid-September. Install bare-rooted specimens as soon as you get them. But, if they're in containers and potted carefully, you can plant them in spring, says John.
“The Chinese traditionally plant herbaceous peonies on the 15th day of the seventh lunar month-mid-August-and tree peonies on the 15th day of the eighth lunar month-mid-September,” he says.
Today, John has about 200 tree peonies, both Japanese and Chinese and other hybrids. (He also grows herbaceous peonies, delphiniums, roses, shasta daisies and foxtail lilies.)
Both herbaceous and tree peonies (which grow on woody stems to a height of one metre or more) revel in climates with cold, snowy winters and are hardy to Zone 3. John leaves most of his out in the open without protection but mulches any that are not deeply planted (i.e., you can see their roots) with a 10-centimetre-deep mixture of soil and manure.
The biggest mistakes you can make when growing peonies, says John, are overwatering and/or over-fertilizing. “They don't need to be coddled. In fact, a tree peony can live for more than 100 years if you take care of it properly.”
John is starting to propagate known tree peony cultivars from China, experimenting with seeds, division and grafting. He hopes to build a small hobby business for other people who would like to grow his seedlings in their backyards instead of depending on foreign imports for selection.
So what began as a form of therapy for John has not only become a positive obsession but may also benefit other tree peony lovers.
Place each tree peony in a hole that's 60 centimetres deep by 60 centimetres wide. Put a handful of bone meal in the hole and plant the bud union 10 to 15 centimetres below the soil. Fertilize with compost or mix and enrich them with additional bone meal. Firm the soil and water well. Plant them at least 1.2 metres apart.
When John Tai visited China, he discovered that tree peonies will grow in just about any soil as long as it's not waterlogged; slightly acidic or neutral soil is best.