New, young foliage will sometimes have a red tinge, so it may be normal. Red can also indicate stress, though ... this could be cold, wet feet*, or nutrient deficiency. Sudden change can bring on stress, as well.

- You don't mention where in the world you are or what cold nights means, so it's hard to assess on that. Also, it'd be good to clarify what variety of blueberries you have (Northern Highbush? Southern Highbush? Half-high?)

- You mention having added acidifiers. Did you test your soil to start to see what amendments it actually needed? Also, what type or acidifiers did you add and when?

*Blueberries like moisture, but not to the extent of drowning; their roots need oxygen, too.

Thanks for your reply. I am located in Bellingham, Washington. I now understand why the new foilage on the plants planted in the ground is slightly red. So I only need to figure out why the small plants in the pots are stressed out. I use a sulfur acidifier. I also have peat moss and pine needles mixed in with the potting soil. I forgot what brand of potting soil I used.

We did have a lot of rain in the last couple of weeks, so maybe that is why they are red?

Thank you,

Kai

Blueberries grow easily in the PNW......this is home to a large number of commercial growers that ship all over the country. And it is very rare to ever get cold enough here in winter for that to be an issue. But growing plants in containers does create some concerns, primarily with potting media and the degree of acidity it contains (pine needles add nothing to the mix - just leave them out). Can you clarify your potting soil contents and the pH? Also, they do like plenty of moisture - one of the reasons they thrive here. I once upon a time worked at a blueberry farm that was planted on top of a slough - very high water table!!