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Pieris Forest Flame, along with most of the other pieris varieties, needs nutrients to produce enough energy to develop properly. Ensuring this starts with the soil you initially plant it in. It continues on to what you feed the plant during the year. The short answer is Pieris need an acidic feed and ericaceous compost.
What soil is best for pieris?
All pieris plants thrive in acidic soil. And that’s soil that’s heavily acidic, not close to a neutral pH. Because of this need, I don’t recommend changing an alkaline soil into an acidic one in order to grow your plant in your garden. This leads you into a never-ending sequence of: fertilising the soil to be acidic; the plant being happy for a while; the soil reverting to be alkaline; and it all starting again.
If you do have an alkaline soil, grow your pieris Forest Flame (or any other compact variety) in a container.
You can then control the pH of the soil and compost that you use in the pot. Use an ericaceous compost as it’s acidic, idealy John Innes as it soil based an retains moisture better.
And consider applying a layer of mulch around the base of the shrub. But place it about 30cm away as a warm and moist environment attracts harmful insects, especially the pieris lacebug.
What and when to feed pieris Forest Flame?
A mulch of well-rotted pine needles is acidic enough to provide the right nutrients to your pieris, if you can get this then use ericaceous compost. Plus organic compost is good for all the beneficial bugs and beings in the environment. Use these once a year, particularly in spring, to give your plant a boost in its growing cycle.
Alternatively or additionally, use a commercial ericaceous fertiliser in spring. This is an acidic fertiliser that may be marked as such. If you can’t find one, look for a fertiliser that’s especially for azaleas or rhododendrons. These have the same nutrient needs as your pieris.
If your soil isn’t very acidic, think about applying both the compost and the fertiliser in the spring. Be on the lookout for your leaves turning a sickly yellow. This could be due to a lack of nutrients or to an infestation of pieris lacebugs. Once you’ve ruled out an infestation of these insects, give your plant another shot of fertiliser to feed your peris Forest Flame.