QUESTION:
I have large Ponderosa Pines in my yard and they drop a lot of needles. I rake them up every year but I must be stirring up something in the soil because the only thing that will grow under the trees are weeds. What can I treat the soil with so grass will grow? I know it’s possible because when I moved in, there was grass under the trees.
ANSWER:
When you rake up the needles and expose bare soil weeds will grow. Weed seeds are there and all they need to sprout is contact with soil and sunlight.
Yes, it is possible to grow grass under your pine trees. However, in heavy shade, it may be more practical to use ground covers or leave the pine needles under the trees as mulch. A lot of pine needles plus shade and competition with the trees for water and nutrients equals no grass or low-quality, thin, weedy grass.
To grow grass under your pines:
- Keep needles from building up
- Plant a species that does well under trees and in shades
- Make sure the grass is getting plenty of water
Fine Fescue (red, Chewings, hard or sheep fescues are all “fine fescues”) is a good choice for shade and grows well under trees.
Large trees will pull a lot of water out of the ground, so make sure you are watering when it is hot and dry.
It is important not to disturb the soil under your trees because you will damage the surface roots. So, to prepare the soil for planting, first kill the weeds with glyphosate (Roundup). Glyphosate will not move through the soil or harm your trees if applied according to the label. Then, aerate with a core aerator and top-dress with 1/2 inch of compost.