Peonies don't need a lot of water; they are considered to be "drought tolerant", and don't like to get their roots water-logged. However, during their first season (when the root system isn't fully established yet), they benefit from regular, deep watering during the dry summer months (and, at any age, if there is a real drought).
For best results, peonies should be fed in spring, and again halfway through the growing season. Use a low nitrogen fertilizer (like 5-10-10). Do the first "feeding" when the stems are about 2 - 3" (5 - 8 cm) high. If using a dry fertilizer, take one or two handfuls and dig it into the ground, but don't dig too deep peony roots are shallow, and you don't want to damage them; also, commercial fertilizer can burn the roots if it comes in direct contact with them. Likewise, it can damage plant stems, so keep any fertilizer at least 12" (30 cm) away from the plant stems.
Peonies really love potash; if you have fireplace ash, take several handfuls (about 2 cups = half a litre), and lightly dig that into the soil around each peony in the early spring. Bone meal is also an excellent, slow-release fertilizer.
Mulch can be any material spread on top of the soil around plants; it is used to retain moisture, control weeds, and/or insulate the roots from temperature extremes. Some of the most common organic mulches are: compost, wood chips, straw, sawdust, leaves, or shredded bark.
Peonies don't really need mulching. However, if your climate is very dry during the summer, mulching can help retain moisture. First put some organic mulch into a bucket, and add water. Let it sit overnight it will soak up the water. Then put a layer of the wet mulch about 2 - 4" (5 - 10 cm) thick around each plant. This will help keep the soil cool and moist during the hot, dry summer months. (Make sure you don't any mulch on the central, growing "crown" of the plant, just on the area around the stalks.)
However, you should remove this mulch before winter and destroy it (ie.e. burn it!); doing this avoids passing diseases between plants.
Don't expect your peony to bloom the first year after planting. In fact, it is better to nip off any flower buds that appear the first year. This encourages the plant to develop its root system during the first year of growth.
Some peonies are floriferous. This means that the can produce more than one flower per stalk. Typically, the top-most flower will bloom first, then one or two of the next lower blossoms, and so on. Some people like this, because it lengthens the blooming season of each individual stem.
However, since only one stalk is producing several blossoms, each blossom is smaller than it would be if the whole stalk only had to produce a single blossom. If you want enormous blossoms, you can remove the side buds as soon as they are visible. This means all the flower-producing power will go into the top-most blossom, and it will be much bigger than if you let the side buds develop as well.
Avoid removing large numbers of leaves when cutting the flowers. As many leaves as possible should be left on the plant to manufacture food. Similarly, don't cut down the foliage after the plant has finished blooming. The plant needs the rest of the summer for the leaves to manufacture and store food in the root system, to grow next year's leaves and blossoms.
Remove the flowers as soon as they fade; pinch or cut them off, just below the base of the blossom. Removing spent blossoms is called deadheading. Deadheading is done to prevent the development of seeds. When the plant makes seeds, it uses up its food reserves, and there will be fewer, smaller blossoms the following year.
If peony flowers are particularly large, the stalks may not be able to support them; sometimes the blossoms can actually droop all the way to the ground. To prevent this, peonies may need to be staked. Traditionally, staking was done by driving one or more stakes into the ground, and the stems were tied to the stake(s) with garden twine or strips of cloth.
Nowadays, there are special supports that you can buy for peonies. These range from very inexpensive, single peony rings made of wire to very expensive, long-lasting peony supports with adjustable rings. A selection of rings and supports is illustrated at the right. They are available at most garden centres and hardware stores. They should be placed in the ground around the emerging stalks in the spring.
In the fall, after the leaves die back, cut the stems down to 3 inches (8 cm). Remove and destroy them to prevent the spread of any possible disease or fungus. If the peonies have just been planted that year, it is recommended that you place a 2 or 3" (5 - 8 cm) thick layer of leaf or straw mulch over the plant, after the ground freezes. Remove this mulch in mid-spring.
Failure to Bloom
Most common reasons why peonies don't bloom:
Too much shade: peonies need several hours of sunlight every day in order to bloom. Too much shade means that they produce leaves, but few or no blossoms. The solution is to dig up the peony plant in the early fall and transplant it to a new, sunnier location. Since peonies don't like to be moved, it may take a year or more before your plant decides to bloom.
Planted too deep: if your peonies have been planted too deep, you may hurry along the flowering time by replanting them closer to the surface of the soil. However, if they've already in place for several years, they may be nearly ready to bloom, since the plant "lifts" itself a little each year as it grows.
Poor variety: a few varieties of peonies just won't bloom if the weather isn't perfect: they might develop large buds that expand but refuse. Nothing to be done, except replace them with another variety.
Disease: botrytis blight is caused by a fungus that over-winters on dead peony leaves, stem, s and roots. The easiest control is sanitation by completely destroying the plant tops in the fall (i.e. either burn them, bury them in an unused corner of the garden, or heave them out with the trash).
Some virus diseases may stunt and deform the growth of your peonies and cause a gradual decline. Each year the plant becomes shorter, somewhat discolored, and may fail to bloom. Nothing to do except dig up the plants and destroy them.
Insects: certain insects, such as thrips, can cause flowers to become deformed and not open. Go to the garden centre and look for an insecticide that works on thrips; follow the directions on the package.
Peonies do NOT like to be moved, so they should be transplanted or divided only when absolutely necessary. A well-established and productive plant may not need dividing for ten to fifteen years, or even longer. However, if your peonies have been planted too closely (i.e. closer than 3 feet (1 metre) apart), they can start to get very crowded, and they should probably be divided. Here's how:
Last revised August 31, 2008