Several years ago we planted some blueberry bushes. They seemed to do well for the first year. However, when they leafed out in the spring the leaves were not a healthy green color. We used grass clippings and manure around their root base but this did not help. After doing some research on the internet we learned that blueberry plants need magnesium and that using epsom salts (magnesium sulfate) will help them. This sounded strange though and so unfortunately we did not try using epsom salts on our plants. They eventually died.
The next year we bought new blueberry bushes and planted them in good soil mixed with peat moss. The first year they seemed to do very well just as before. However, in the spring of the following year they did not look very healthy after leafing out. Not wanting to lose these new bushes we mixed one table spoon of epsom salts and one table spoon of apple cider vinegar in two gallons of water and watered the plants. Within two days they were greening up nicely and looking much healthier. We then sprinkled a few table spoons of epsom salts around the root base of each plant to provide long term magnesium.
Our blueberry bushes are now doing very well and producing blueberries which we have begun harvesting this year. Our chickens have also been harvesting blueberries as well but the ones we have gotten our hands on have been very good.
To summarize, If you are trying to grow blueberry plants and they do not look as green or healthy as when you first got them. Try one table spoon each of epsom salt and apple cider vinegar in one or two gallons of water. The acidity of the apple cider vinegar helps the plants absorb the epsom salts. You can then sprinkle a few table spoons of epsom salts around the root base of your plants for long term absorption.