I also have the Pieris Mountain Fire -- Now thinking back I had to determine where and what exact micro climate , was going to make this fussy plant happy for lack of a better term. Anyway,I north facing partial shaded spot That's where the trouble began with a bit too much sun. The foliage gradually turned a yellowish green from a meduim green. It still gave me color in fall but there's something just not right. Growth became so slow and this last winter just made it look like it's bailing. Then I read about low iron can influence color. Wondering if this thing is suffering from low iron. Here's what I'm trying: I 've transplanted it close to a shadier place along the same fence but under a Spartan Juniper. I've found Plant Prod water soluable Chelated Iron at a local building store. I'm giving this a dose now and seeing if things green up. If they do there's a good chance all other values will improve Worth a try ... This is my prognosis

Acute stress from heat and/or water shortage. What have the prevailing temps been recently?

Lush new growth will wilt in the sun even when the plant has plenty of water until the new growth has had enough time to harden off. As with rhododendrons, placing a pieris is a balancing act between enough sun to encourage bloom and enough shade. Morning sun followed by afternoon shade is best, but often not possible. Another reason for placing pieris in at least a partially shaded area is that they tend to become magnets for lacebugs in sunny locations. As for planting in the ground, there are some variables to consider if you wish to do this late in the season. For any ericaceaous plant - pieris, rhododendron, azalea and others - the size of the root ball is important. Small one or two gallon plants will often not have enough time to develop a root system large enough to carry them through cold weather. This has certainly been true in the last two Maine winters. Best to wait for spring planting. Even large plants will need the protection of burlap or some other wind and sun blocking shelter for the first one or two winters. They will also need to be watered right through fall until the ground freezes.. If you intend to keep this one in its pot over winter, then the roots will have to be protedted from deep cold.

That could be drought stress or fertilizer burn. skuiiy: We bought the plant with the shown plastic pot and kept it in there since it seemed to be doing well & producing flowers and fruit. A plant from the nursery producing fruit is often doing so because it's stressed. When tomatoes are stressed, they fruit because the plant rushes to reproduce before it dies. So assuming it's happy because it's fruiting could be incorrect. Even if the pot is OK now, it won't be much longer unless that plant is a dwarf or small determinate. skuiiy: -Gave it liquid fertilizer. -Added about a spoonful of epsom salt to the soil/mulch mix it's in and mixed it in a bit. Epsom salt is really only necessary if the plant has a magnesium deficiency. If not, it could cause problems. Also, it's possible you've given the plant too much fertilizer, which can manifest as leaf burn skuiiy: now I'm watering(about 2 cups of tap water, instead of just 1)every other day starting today to see how that goes. First: Pot it in a much larger container. Gently knock off as much of the current potting mix as possible so that almost all of the mix is fresh, as this will help correct the problem if nitrogen burn is the problem. Use a normal, fluffy, well-draining potting mix, not a mix advertised as moisture-retaining, and not anything labeled as "garden soil". Mix water into the mix well before putting it in the pot, as peat-based mixes can initially repel water if they're dry. Second: Don't measure your water or water on a set schedule. To determine when to water, stick your finger down into the mix a couple inches. If it's dry, water and water very deeply, until the water is running freely out of the bottom of the pot. If it's still wet a couple inches down under the surface, hold off. In your climate, when it gets hot, don't be surprised if you have to water daily. As for fertilizer, you can give the plant a dose according to instructions once a week or every two weeks (depends on how frequently you have to water), or you can water at very dilute strength with every watering (dilute more the more frequently you have to water).