I have a part of my backyard that is under pine trees. The whole area was a pine farm until about 5 years ago, when it was turned into a subdivision. The trees are mature and about 60 - 70 feet tall. The area that I need to improve the soil in is right on the edge of the trees. Last summer we tried to grow a vegetable garden in the same soil and was a complete waste of time. It is in the sun, south facing.

I have azaleas, hydrangeas and magnolias trees in the area adjacent to where we had the garden and in the same type of soil. The magnolia trees are growing taller, but aren't full. The azaleas didn't bloom very well last spring. We just planted the hydrangeas this fall. When we planted them we fertilized with milorganite.

I'm afraid that the things we have planted, even though they all like the acid soil, won't get enough nutrients. So please let me know what sort of fertilizer would be best for that area.

Answer #1 · Brent Wilson's Answer · Hi Darlene,

To "sweeten" or make acid soil more alkaline, you would apply lime. As for how much lime you need to apply, this might require a soil test, and might depend on what type of plants you want to grow.

Most vegetables prefer well-drained, fertile soil with a neutral pH (around 7). Local nursery and garden centers usually sell pH soil test kits. In the absence of a soil test, I'd recommend applying at least 40 pounds of pelletized lime per 500 square feet for a vegetable garden. I'm building a new 400 square feet veggie garden this winter and will apply a 40 LB bag of lime. I'll also till in a several inch layer of mushroom compost to the existing native soil. Will also make sure the bed is raised so it will be well-drained. Sometimes it takes a couple years for garden soil to get really good...so I wouldn't give up on growing vegetables.

Regarding azaleas and magnolias, these should do okay in an area where there's a lot of pine trees and therefore acid soil. Milorganite is what I use to fertilize all the acid-loving plants in my yard and so far so good. It also helps to repel the deer that live on either side of our property. Since Milorganite is a natural fertilizer you might have to apply more of it to see good results. It's non-burning so you don't have to worry about applying too much. You could put 5 pounds of it on one azalea bush without doing any harm to the plant. If you want to use another fertilizer to provide some additional nutrients and elements apply a shrub and tree type fertilizer that contains a "micronutrient package." You can also have your soil tested through the local extension service to get more specific results for nutrient deficiencies.

Regarding hydrangea, the "mopheads/French" hydrangeas (hydrangea macrophylla) will tolerate a wide range of soil pH. The acidity of the soil can and will change the color of some hydrangeas. Add aluminum sulphate to alkaline soils to turn pink mophead hydrangea blooms to blue. Add lime to acidic soils to turn blue to pink.

Hope this info helped,
Brent)