I purchased 2 sea holly plants last year. I have not planted them in the ground and so far they have not produced any flowers and the leaves keep going yellow. What am I doing wrong?
Yellow leaves normally signal stress of some kind. There are a number of reasons why the leaves may turn yellow. One might be overwatering. Too much water causes yellowing of the leaves and mandevilla do not like overly wet feet. Another possibility could be too little water. If this is the case, the yellow leaves would be curling up as well. This article will help you determine which may be affecting your peach tree: https://www.gardeningknowhow.com/plant-problems/environmental/plant-leaves-turn-yellow.htm
Stress would also prevent the plant from flowering as will a lack of phosphorus. Bone meal added to the soil will help should phosphorus be too low. A soil test will let you know for sure.