How to Grow and Care for Tree Peony

Tree peonies (Paeonia suffruticosa) are deciduous sub-shrubs that bloom for a week to 10 days in mid to late spring with big, fragrant peony flowers. The frilly flowers are much like those of their cousins, the familiar herbaceous perennials, Paeonia lactiflora, but larger.If you love peony flowers, tree peonies might be the perfect choice.

Once their spectacular frilly blooms have died, the green-leaved shrubs provide an attractive backdrop for other plants. The plant can live up to 100 years and is cold-hardy from 20 to -40 degrees Fahrenheit. Plant tree peonies six weeks before the first freeze in the late fall, but not in the spring, which weakens them.

Tree Peony Care

Tree peonies sold in garden centers are typically the result of grafting. The scion is a tree-peony cutting that has been grafted onto an herbaceous rootstock. Be sure to plant the graft union at least 2 inches below the soil surface. Some nurseries recommend more; follow the instructions that come with the plant. Often, there is a plastic ribbon indicating the recommended planting depth. Proper depth will promote the establishment of the scion's root system.

Like the herbaceous peony flowers, tree peonies do not like to be transplanted or planted in pots. Find a suitable, permanent home in which to establish them when planting. Tree peonies are very slow growers and may take three years before new plants fully establish and flower. Once established, they need little maintenance.

Light

Grow tree peonies in full sun to dappled shade. The flowers may suffer in hot summer sun so providing some shade helps. It can be tricky, however, deciding where to plant a tree peony because though the plant thrives in full sun and grows well, its blooms fade much faster than if it grows in dappled sunlight.

Soil

These plants like to grow in well-drained ground, with a soil pH that is neutral or slightly alkaline. They will thrive in a loamy soil fortified with compost, which is also called friable soil.

Water

Tree peonies have medium water needs and should not be overwatered. It's not a good idea to plant them where they will be watered by lawn sprinklers. Water deeply after the top 4 inches of soil have dried out.

Temperature and Humidity

They grow best in climates with hot summers and cold winters, making them great plants for much of the eastern, midwestern, and western United States. Tree peonies have chilling requirements, so they grow best in regions that experience cold temperatures during the winter. The further south you go in their range, the more sense it may make to grow them in dappled shade. For fall care,mulch to provide additional winter protection if you live in an area where the plants are only borderline-hardy.

Fertilizer

Adding a layer of compost or manure to the soil in spring will give the shrub a boost of nutrition to start the season. Many gardeners also like to feed their tree peonies with a foliar spray of fish emulsion later in the season.

Types of Tree Peony

• P. suffruticosa 'Red' bears a gorgeous pink flower (not red) and blooms relatively early in spring.
• P. suffruticosa 'Kinkaku' has bicolored flowers of pale yellow with pink edges and blooms a few weeks later than P. suffruticosa 'Red'.
• P. suffruticosa 'Kinshi' is also called the "Golden Bird" because it bears huge flowers in a golden-yellow color.
• P. suffruticosa 'Qing Xiang Bai' produces single blooms (most tree peonies have double blooms).

Pruning

Pruning is rarely necessary on tree peonies, much because the buds need to be preserved. They are not like herbaceous peonies, which need to be cut or die back to the ground each year. However, you should prune the shrub to remove dead branches. If there are branches that result from suckering from the herbaceous rootstock, remove those too. When you do prune, wait till early spring to perform the operation because you can see the new buds and you can then avoid lopping them off. Avoid pruning in fall, as aboveground growth helps shelter the root system in the winter.

Propagating Tree Peony

Propagating a tree peony can be complicated since it often requires grafting. But if you have the right type of shrub, you can propagate by division. Avoid dividing a shrub that has only one or two trunks or stems because there won't be anything to divide if you dig it up. In the fall, find a multi-stemmed shrub with plenty of roots that have spread so you can divide them. Dividing a tree peony requires patience and strength. Take these steps once you've identified a good candidate for dividing:

1. Begin by digging around the plant's dripline, then tugging and lifting it from the ground. Be gentle to avoid damaging the root system.
2. Carefully wash the soil off the roots.
3. Cover the roots with a barely damp cloth and allow the plant to rest for a couple of hours so the roots can dry a bit.
4. With sterile garden cutting tools, cut off the herbaceous peony root that is likely still attached to the root system from the original grafting. That root will be darker, thinner, and a bit more swollen than the tree peony's roots (you can always replant that herbaceous peony root.)
5. Divide the remaining roots carefully. Each division should have a stem and a root to make it viable when replanted. First, try pulling the roots part rather than cutting, but you may need a snip or two to complete the division. Sometimes the tree peony will naturally pull apart from its original grafted root.
6. Cut off any rotted or blackened roots once it's divided.
7. Immediately prepare the hole to replant and water the divisions.
   

How to Grow Tree Peony From Seed

Mature tree peonies are a source of seeds to use for propagation. To harvest a tree peony's seeds, do not deadhead the shrub until mid to late August and early September. The shrub needs the summer to spend energy ripening the seeds. Then take these steps:

1. When the seed pods swell and turn darker brown in August or early September, harvest them by snipping the seed pod off right below the pod.
2. Extract seeds from the pod. The darker seeds (black or dark brown) will be viable. The best darker ones will also start to show tiny cracks in the coating which means they will likely germinate.
3. Immediately plant the seeds into either the ground or clay or plastic pots (10 or 12 inches in diameter) filled with garden soil mixed with sand and perlite to aid drainage.
4. Plant seeds a couple of inches apart and just as deep. If placing seeds in the ground, choose a spot with dappled sun.
5. Cover the buried seeds with mulch for winter and pest protection.
6. Water the pots or ground every so often to prevent the seeds from drying out.
7. If in pots, transfer seedlings into the ground in the spring.
   

Overwintering

Young plants should be lightly mulched to protect the roots from frost heaves. Wrapping the shrub in burlap can protect buds if there is a surprise blast of frosty weather in the spring. Do not cut tree peonies back for the winter.

Common Pests & Plant Diseases

Pests do not generally care about tree peonies. However, rabbits are notorious for damaging tree peonies in the winter. Put chicken wire or cloth on the plants in the fall by late November to protect the tree peony shrubs.

Otherwise, you may find ants on flower buds, but they will not damage the flowers. Scale and thrips present two more dangers, but these insects can be eliminated with sprays of water or insecticidal soap. Avoid pesticide runoff around a tree peony or it could die.

Tree peonies have some (but not all) of the same issues as herbaceous peonies when it comes to diseases and may experience canker, leaf blight, and stem wilt.

How to Get Tree Peony to Bloom

It doesn't take too much to achieve a tree peony shrub full of luscious, fragrant, big, and bold flowers. A young tree peony may not bloom right away and you'll need to remain patient for a couple to a few seasons until it matures enough to develop buds. It does help to know that a tree peony sets its buds in the summer before it blooms. That's why it is important to take care when pruning this shrub or else you risk shearing off all the new buds which will affect the number of blooms the plant produces.

To encourage blooming for the next year, you can cautiously deadhead this shrub. Only deadhead after it has bloomed, which should be around June. At this point, the plant is going to expend a lot of its energy during the summer to ripen its seeds in the seed pods. Helping the plant spend its energy on new growth and buds means deadheading properly. With a sterilized cutting tool, snip off the seed pod right below the pod so you don't disturb any emerging buds.

Common Problems With Tree Peony

Once established, a happy, mature tree peony will show rare signs of problems. But, be on the lookout for these signs of issues:

Buds Don't Open

Though tree peonies are cold-tolerant, a light frost may have damaged the buds. However, the tighter the bud, the more likely it can recover as the weather warms up. Never touch frozen buds or they could snap off.

Leggy Shrubs

It's normal for mature tree peonies to become leggy. The way to mitigate leggy plants is through long-term care, which means slowly pruning the tree over a couple of seasons. Trim slightly in both the spring after flowering and fall to minimize stress to the shrub and its buds.

Mature Plant Doesn't Bloom

You may suddenly see a vast decrease in your plant's blooms. Check to see if it's buried deep enough because exposed roots can stress the plant. Also, make sure your older tree peony is not competing with weeds and other plants for sun and water.

Shrub Blooms Twice

Though it may seem as though you hit the jackpot with a twice-blooming tree peony, unfortunately, that's not the case. If you are seeing one burst of blooms, then a second burst a few weeks later, you have a grafted tree peony with an actively blooming herbaceous peony root. The tree's blooms will suffer at the hands of the blooming herbaceous peony. To fix this issue, cut down the herbaceous single stalks, stems, and shoots to allow the tree peony to flourish.

From: thespruce