Saturday, July 30, 2011
Recently, I took an on-line class given by Dr. Tony Koski, professor at CSU and Extension Turfgrass Specialist. I learned that our soil here in Colorado is very high pH--free lime. Although pine needles fall in abundance, there could never be enough pine needles to lower the pH. Fallen needles may SLOWLY make the soil more acidic, but more likely for the better since it neutralizes the lime. It takes decades to change pH and will not decrease by more than .5 units. There goes that myth!
Following are the some of the real reasons many things, especially turf, don’t want to grow under these trees:
The turf tends to be smothered by a thick mat of pine needles.
Dense, year round growth leaves little light. The only thing that will get through is ‘left over light’, according to Dr. Koski. This light lacks intensity and quality. This ‘left over light’ is what the tree does not use for photosynthesis.
Any other plant will struggle with below ground competition—tree roots competing for water and nutrients. Our tree roots here in Colorado tend to be fairly shallow.
Evergreens, with their dense growth, shed rain to the outside of the tree line, so it’s dry under the tree. Without adequate water and nutrients, most plants will suffer in this setting.
But, what does grow under pine trees?
All three of these plants will need additional irrigation, however, since lawn sprinklers and rain can’t reach them well, but it’s worth the extra time.
So, at least we know there are choices. The easiest one would be to allow a natural mulch of needles to occupy that space, and that is just fine. In fact, I find pine needle mulch quite attractive! The other choice is to try one or more of the above plants, especially if you must have flowers in as many places as possible!