How do I apply phosphorus to my plants? Do I water after I put it down? For lilac bushes around 5' tall how much do you think I should use--no flowers. Same for hydrangeas.Thanks much--Live in Flemington NJ.
The easiest method to add phosphorous to your plants soil is to use Bone Meal.
Adding good organic compost to your soil around the plants will also help.
Follow the directions on the packaging for the Bone Meal product that you choose.
I generally scatter the recommended amount and rake into the top soil. Then water in.
Here are some articles with more information.