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Are you thinking of growing peonies but are unsure of the ideal soil conditions? If you get the wrong type of compost, there is a chance that it can lead to stunted growth. But will ericaceous compost be suitable for peonies?
No. Peonies require slightly acidic soil to neutral, between six to seven on the pH scale. Ericaceous compost, though, has a pH range between four to five, making it too acidic for peonies. Instead, a neutral to alkaline compost is required, preferably a variety with low peat levels.
Thankfully, peonies aren’t too fussy about their soil conditions. You shouldn’t have too many problems getting free-draining soil with the right pH level.
Keep reading to learn more about the flowers and plants that can be planted successfully in ericaceous compost and about types of compost that are better for peonies.
Why Ericaceous Compost Is Not Suitable for Peonies
Ericaceous compost has a pH of between 4 and 5
. Ideally, peonies require soil with a pH of between 6 and 7. If the compost is too acidic, it will not be able to produce healthy flowers, and the entire plant could end up withering away.
This is especially true when peonies are rooted in a small space, such as within a pot or planter. They cannot grow their roots outside of that environment, so getting the type of compost correct is important. Peonies planted in flower beds also need a higher pH, but the damage may not be as severe in a bigger surface area.
How can you find out the pH of your compost?
There are three methods you can use to find out the pH of your compost easily. The first is with an at-home pH tester kit. A reputable test kit can be found on Amazon here. Follow the enclosed instructions to receive the best results.
You can also send a sample of your compost to a laboratory for testing. This is the most accurate of the three options, but it can be costly and time-consuming. Ensure you research before sending off any samples or handing over any money.
If you cannot access one of these tests, there is a DIY method you can employ that may be less accurate but will still give you a rough estimate of whether the soil is more acidic or alkaline.
Take your soil sample and add ½ a cup of filtered water. Once it has settled, add ½ a cup of plain vinegar. If there is a reaction where you see fizzing or bubbling, the soil is more alkaline. If not, it is more acidic.
Which compost is best for peonies?
It has already been established that peonies prefer neutral to alkaline compost. But what types of compost on the market fall under this category? According to British Roses, the most recommended brand is John Innes No 3.
This is because it contains no manure and a low amount of peat (both detrimental to a peony’s growth), has an alkaline pH, is loam-based (containing real soil), drains well, and contains many nutrients vital to a plant’s development. You can find this exact brand on Amazon here.
Another popular brand of compost for peonies is Miracle-Gro. They sell a handy all-purpose compost suitable for beginners and can be used for any type of plant or flower regardless of its pH needs. A peat-free version can be found on Amazon here.
While the soil is important, it isn’t the only thing to consider when planting a peony. Here are some of the other things you should consider:
What kinds of flowers can be planted in ericaceous compost?
Some several plants and flowers prefer ericaceous compost and a lower pH. These include:
- Roses
- Rhododendrons
- Azaleas
- Heather
- Camellias
- Blueberries
- Pieris
- Asters
- Raspberries
- Juniper
- Cranberries
- Magnolias
- Daffodils
All of the above plants fall under the Ericaceae branch of botany, hence the name of the compost. If these plants are set into alkaline soil, they will also suffer the detrimental effects of nutrient deficiency, such as yellowed leaves, slow growth, fewer flowers, and even death.
Why has the use of peat in compost declined in popularity?
Peat is the surface layer of soil made up of organic materials built up over time, such as dead plants, and forms only under certain environmental conditions. These include a lack of oxygen, high acidity, and a lack of nutrients.
Years ago, peat was a key component in many big brands of compost. Recent studies have shown that the process of harvesting peat was causing damage to the environment and the species of plants and animals that lived there.
Peat can mainly be found in boggy marshes on low-lying land. These bogs are unique because they contain a lot of carbon and water, so many species can only survive in this habitat.
Taking the peat meant that these species no longer had a place to live and therefore had to move to a different environment or simply die.
Which other plants prefer alkaline soil?
According to Gardener’s World Magazine, several different plants prefer alkaline soil. These include:
- Lily of the Valley
- Ornamental clovers
- Lavender (all but one species)
- Thyme
- Rosemary
- Artemisia
- Polemoniums
- Honeysuckle
- Syringas (also known as lilacs)
These plants tend to be less popular with gardeners due to many being wildflowers or herbs, but some are still known as pretty garden plants to have at home. Natural alkaline soil can be found in environments where there are elements such as chalk or limestone present.
What happens if compost is overly acidic or overly alkaline?
It is very rare for compost or even natural soil to have a pH that is too high or too low. However, if this happens, then the plants rooted in it will be more likely to fail to thrive. This can happen even if it is in an acidic bed and usually thrives in acidic soil or in alkaline soil and is an alkaline-loving plant.
An increased pH can kill the plant or weaken it severely through malnutrition. The signs are much the same as when it is planted in the incorrect type of compost; yellowed leaves, delayed flowering/growth, and death of the plant.
How can you best care for your peonies?
Peonies are strong plants that usually require little maintenance so long as they are planted in the correct conditions. There are three species of peony; herbaceous, tree peonies, and intersectional hybrids. Each type has different characteristics:
Herbaceous:
- Flower in spring/summer
- Die in winter and fall back to ground level
- Prefer alkaline soil
- Needs to be in full sun
Tree Peonies:
- Tall shrubs
- Maintain their shape throughout winter
- Can tolerate acidic soil if necessary
- Needs partial sun coverage
Intersectional Hybrids:
- A cross between the former and the latter
- Rarest species
Some species of peonies have flowers that can grow to an enormous size if they are cared for properly, and all flowers come in a variety of colors, making them a popular choice for novice gardeners.
As well as needing to be planted in an alkaline-based compost, they require soil that stays moist yet drains easily to avoid waterlogging. They also need at least partial sun coverage in the daytime, but if they are herbaceous, then they preferably should have the benefit of full sun coverage.
Species with larger flowers may need support to keep them from overbalancing and wilting. This can easily be achieved by tying them to a plant support stick with string, though be aware not to tie them too tightly.
You should also be aware of the depth in which they are planted. Soil depth can be the difference between a thriving plant and a dead one, so make sure they aren’t planted too deeply. Also, avoid overwatering newly planted peonies, which causes problems later.
Sources
- https://www.gardenersworld.com/how-to/grow-plants/ericaceous-compost/
- https://www.britishroses.co.uk/
- https://www.gardenersworld.com/plants/best-plants-for-alkaline-soils/
- https://www.gardenersworld.com/how-to/grow-plants/how-to-grow-peonies/
