Peony Care & Love
Peonies are a wonderful and hardy plant that can thrive without being disturbed for in excess of 50 years, some reports say even more than 100 years! However in order to have long lasting success some care and attention must be given to establishing the plant in the correct way. There are many excellent recourses around and the comments below are meant to summarise the most important aspects rather than go into extensive detail.
Like any plant you want to start with a healthy specimen. Whilst some sellers sell peony tubers with only 1/2 eyes its best to try and source plants that have 3/5 eyes each (pink fleshy protuberances from the tuber). These plants will grow bigger quicker and should deliver blooms faster accordingly.
If you are trying to grow peonies in a slightly warmer region than would otherwise be advisable pick the earliest flowering variety you can get, as these should require fewer chill hours to bloom successfully. A variety like Coral Charm for example flowers very early in the season and may do better it a warmer climate. A general rule is that if you can grow apples you can grow peonies.
THE PLANTING SITE & CONDITIONS:
Peonies are hardy plants and whilst they do need water, particularly during spring, they do not like wet feet and a prone to rot. If you're soil holds a lot of water try amending your planting hole with good compost and/or bio char to help with drainage. Alternatively create a raised planting bed.
Peonies like full sun and being planted in a shady spot is key reason they fail to flower. Plant it in the sunniest spot possible in your garden and you will be rewarded.
Reports on desired soil acidity vary but by and large a soil type very close to neutral (7) should stand you in good stead. In Australian soils which are normally acidic, it can be best to add a cup or more of lime to the site prior to, or at the time of, planting. A good addition of compost will help provide some nutrients to the plant when it starts to grow come spring.
One of the most unique aspects to planting peonies is that they should be planted very shallow to the soil surface. In the Australian context this is particularly important so that the plants get as much of a chill over winter as possible. Even in Alaska in the USA peonies are only planted 2.5 - 3cm below the soil surface.
Whist 2.5cm is the general rule I would shy away from a more shallow planting as long as the plants don't end up being directly exposed to the elements.
My husband and I have a saying "chill like a peony". He came up with it when I was trying to have a serious conversation about the chill requirements of different peony varieties. However, after hearing it once I thought it was very apt as peonies certainly do need to 'chill' just like the rest of us to ensure we look beautiful in Spring.
Peonies need a large number of chill hours over the winter to properly bloom come the spring. It is known that different varieties need varying amounts of chill hours however finding variety specific information is very difficult and is something we are hoping to record over the coming years.
Most of Australia isn't naturally suited to growing peonies. Which can be pretty devastating news to a new peony lover. However there are a couple of options depending on desperation and to be honest finances.
Naturally Cold Region: If you grow in an area that commonly gets winter frosts and know the people in your region grow fruits that require a chill to produce (apples, cherries etc) then you can probably grow peonies without much interference and might want to start with early flowering varieties for the best chance of success.
Ice packs: Some people in borderline areas could try giving their peonies a bit of a helping hand by providing them with ice packs over night to help get their chill hours up. Depending on the number of plants you have fill an ice cream container with water and freeze during the day. Remove the block of ice and place it over the plant site. It will defrost overnight providing water and cool conditions.
Cool room: If you had access to a cool room or a domestic freezer room peonies in pots that could be moved in there over winter and the brought outside for the start of spring would probably do really well. Just be careful not to let the soil completely dry out over the winter period. If planted in the ground we would water them once a week and a similar approach may be best. If theory you could have peonies in even the warmest regions with this approach.
Peonies do not like wet feet so overwatering is something to be careful of, particularly if your soils tend to retain moisture. Peonies, whilst generally being disease resistant are susceptible to types of fungal infections such as botrytis. One measure to help avoid this is having drip irrigation for peonies rather than sprinklers.
Also ensuring there is good distance from other plants to encourage air flow is a wise preventative measure. If your peonies are prone to fungal infections and moving them is not desired you can use an anti fungal treatment from the start of spring until flower blooming has finished.
Some varieties need a more consistent water supply in order to flower properly such as Sarah Bernhardt and perhaps should be avoided for best results.
PRUNING & FEEDING:
Pruning is very important in the Autumn to avoid peony diseases setting in. In April cut your peony plants back completely to ground level (so that no plant is visible above ground). Do not compost your cuttings as they will likely promote botrytis.