I have a 3yr old Grevillea 'Long John' in the ground. It is thriving and looks beautifully alive. But for the last 3 months or so the foliage is turning from a dark green to yellow. I had been watering it twice a week for 8 minutes and when I noticed it getting lighter I changed it to 8 minutes once a week. It did not seem to make any difference, it is now almost yellow. But it still looks absolutely blooming. WHY IS THIS PLANT TURNING YELLOW?
Grevillea ‘Long John’
Certified GKH Gardening Expert
This sounds like a pH issue. Is this close to any water outlets, or maybe the street? It appears to be experiencing some pH swings. I would recommend applying dolomitic lime to the area around the tree. Here is a link to some articles that will help: https://www.gardeningknowhow.com/houseplants/grevillea/