Q. I’ve added some new shrubs under pine trees and they
are all doing poorly. I’ve read that pine needles are acidic and can change the
pH balance in the soil. I’ve also read that’s not true. Could the pine needles
be affecting the new shrubs?
A. I am on the side of “it doesn’t make much
difference”. Yes, pine needles contain a lot of resin and they don’t break
down quickly. But having them on the surface of the soil, or mixed into the soil
at about 5% of the soil volume, makes no difference at all!
difference”. Yes, pine needles contain a lot of resin and they don’t break
down quickly. But having them on the surface of the soil, or mixed into the soil
at about 5% of the soil volume, makes no difference at all!
 |
| Using pine needles like these from a Chir pine problem in desert soils when used as a surface mulch. If they are mixed into the soil, try to keep the amount less than 10% by volume. They decompose much faster when they are shredded. They help lower soil pH which is very important in desert soils. |
Besides the resin, there is some slight lowering of pH (more
acidic) which in our soils is actually helpful. Hopefully you amended the soil
under pine trees with compost at the time of planting.
acidic) which in our soils is actually helpful. Hopefully you amended the soil
under pine trees with compost at the time of planting.
Digging a hole large enough for plants under pine trees
can be difficult because of the roots of the pine. Don’t be afraid to cut pine
roots when planting. Allow these cut roots to heal 24 to 48 hours before they
are buried in the soil again.
can be difficult because of the roots of the pine. Don’t be afraid to cut pine
roots when planting. Allow these cut roots to heal 24 to 48 hours before they
are buried in the soil again.
Look closely at the amount of light these plants are
receiving. Some plants grow nicely with 50% or more sunlight available to them.
Others need much more than this for good growth. As an example, Bermudagrass
can handle about 10% shade while tall fescue can handle nearly 50% shade.
receiving. Some plants grow nicely with 50% or more sunlight available to them.
Others need much more than this for good growth. As an example, Bermudagrass
can handle about 10% shade while tall fescue can handle nearly 50% shade.
Generally speaking, flowering plants need lots of light
compared to non-flowering plants. Signs of a lack in light can be a general
failure of the plants to thrive, leaf drop and a general thinning of the canopy,
and leaf yellowing. You may have to remove some of the lower limbs to allow
enough sunlight to the plants growing beneath the canopy.
compared to non-flowering plants. Signs of a lack in light can be a general
failure of the plants to thrive, leaf drop and a general thinning of the canopy,
and leaf yellowing. You may have to remove some of the lower limbs to allow
enough sunlight to the plants growing beneath the canopy.
This link about pine needle mulch is from Clemson
University in South Carolina where most soils are acidic. Our soils are nearly
100 times less acidic (more alkaline)
than those in many parts of South Carolina!
http://www.clemson.edu/extension/hgic/plants/other/compost_mulch/hgic1604.html
University in South Carolina where most soils are acidic. Our soils are nearly
100 times less acidic (more alkaline)
than those in many parts of South Carolina!
http://www.clemson.edu/extension/hgic/plants/other/compost_mulch/hgic1604.html
The pH scale is logarithmic, not linear. A pH of 5.5, a
common pH value for acid soils, is 100 times more acidic than our soils with a
pH of 7.5. Our soils commonly range from 7.8 – 8.5.
common pH value for acid soils, is 100 times more acidic than our soils with a
pH of 7.5. Our soils commonly range from 7.8 – 8.5.
Pine needles decompose
more quickly if they are cut or shredded.