Whether you’re planting bulbs, trees or perennials, the best time to do so is when they’re dormant – before they begin their active growth. The optimal planting time depends on what you’re planting. Perennial plants are best planted in spring, but it’s better to plant peonies in the fall.
Why it’s best to plant peonies in the fall
Peonies are available as growing, potted plants in spring, but this has more to do with satisfying the demands of the market than what’s best for your peony. Not that they can’t be successfully spring planted, but you run a fair risk of disappointing results. Besides, the selection from peony nurseries in the fall is much larger. Considering how long they live and how few most of us will plant in our lifetime, why not do it right? Don’t be surprised to spend more that $30 for a good variety. They’re worth it and for heaven’s sake what else can you grow and enjoy for the rest of your life for so little?
Herbaceous peonies are by far the best known and beloved. They like a fertile soil, but tolerate a range of types provided they drain well. A minimum of six hours of sun is best. Nurseries lift their peony roots in the fall, dividing them into pieces. Each piece should have three to five “eyes”. These eyes will produce next year’s stems and flowers. Peonies don’t like being moved around, so choose your planting site carefully, considering the sunlight and your peony’s mature size. Give them room. Small as that root looks now, it will get much bigger.
Easy as they are to grow, there is one critical factor that must be addressed when planting – the depth of the root. Actually, it’s the depth of the eyes that matters. If planted too deeply, your peony may not flower for many, many years. It will grow, but not flower. These eyes are the pink or white buds you’ll see at the top of the root (crown). Dig a hole larger than your root and orient the root so that the eyes are roughly on one plane. Hold the plant carefully in the hole and fill in the soil, making sure the eyes are 1 1/2 to two inches (3 to 5 cm) below soil level. Chances are you may have piled the excavated soil next to your hole which makes this measurement tricky, so I place the excavated soil elsewhere and lay the handle of my spade across the hole to show the soil level. Novice gardeners sometimes mistake the thick roots for stems, planting the crown upside down. There shouldn’t be any part of the root showing above ground when you’ve finished. Tamp the soil down gently. There’s no need to water unless you don’t expect any rainfall before winter.
The problem with planting potted peonies in the spring is that there are no eyes visible, just the growing stems. The eyes may or may not be at the right depth in the pot. Without seeing the eyes you won’t know where they are when you put your potted peony into the garden. Besides, the selection is huge in the fall, the prices cheaper and many specialty peony nurseries only ship bare root in the fall.
Unlike herbaceous peonies, tree peonies don’t die back to the ground every winter. They’re equally long lived, but their woody branches remain above ground in winter. They, too, like lots of sun, but light-coloured varieties like light dappled shade at midday to keep them from fading. Five hours of sun will probably do. Tree peonies also hate being moved and they grow larger than their herbaceous cousins so give careful thought to their site. Give them a fertile, well-drained soil. They were first hybridized in China (their native country) and Japan, but there are also many fabulous North American hybrids.
Tree peonies are grafted to an herbaceous rootstock. They can’t readily be divided so grafting is the easiest and most economical way to produce them. This isn’t an easy or quick process. The graft should be a few years old and the plants have several branches. A good tree peony can cost over $100, not bad considering they sold for their weight in gold in imperial Japan centuries ago. Their spectacularly crepe-textured flowers come is a wide range of colours, often with contrasting flares, and bloom before their herbaceous cousins. They can be purchased potted in the spring and can certainly be planted then, but experience still strongly suggests bare root, fall planting is best because, unlike potted plants, their roots haven’t been cut off to fit in a pot. Bigger roots will give you a bigger, better plant.
You’ll need a hole big enough to accommodate the roots and deep enough to situate the graft a minimum of six inches (15 cm) below soil level. The reason for this is threefold. First, it encourages the tree peony to grow its own roots, overtaking the grafted herbaceous rootstock. The second is to ensure that there’s enough of your precious tree peony to grow back should it ever be broken off at ground level. Thirdly, it discourages the rootstock from producing its own foliage and overtaking the tree peony grafted to it. Keep an eye out for non-woody stems with different foliage. If you see them, just dig down and cut them off where they join the root.
I wouldn’t be surprised if you’ve never heard of Itoh hybrids. They first came to North America from Japan in 1963, so are a relative newbie to the peony world. In 1948 the gifted Toichi Itoh successfully crossed an herbaceous peony with a tree peony. From the initial 36 seedlings have come the many varieties we have today, combining the colours and textures of the tree peony with the deciduous habit of their other herbaceous parent. They share the soil and sunlight and critical planting depth of their herbaceous parent. Fall planting is best for these, too.
Peonies are very tough plants. I remember the first advice I got (and shared) about moving them: “Dig up the rootball being careful to minimize root disturbance.” Egads, I said when first trying to move a long-established one, discovering it had a VERY deep root system. Short of using a back hoe, there was no way I could get it all.
All you really need is the crown and some of the roots. Just cut off the roots you can’t dig out. Wash the soil away to get a better view of the eyes. You can divide it into as many pieces as you want provided each piece has at least five eyes. I’ve also discovered that those roots still in the ground can grow back, so don’t be surprised if the original plant comes back.