The space under pine trees is often a very difficult area to landscape. It is true that constant needle drop often leads to more acidic soil conditions. In Colorado this could actually help since we have fairly alkaline soil to begin with and plants prefer it to be neutral or a bit on the acidic side. The biggest problems arise from lack of sun and definitely lack of water. Large pine trees and evergreens block most of the precipitation that helps provide moisture to your landscape. They also have very fibrous and prolific root systems that effectively drink lots of water from the ground and will usually outcompete most plants that are planted there. However, given enough water most shade tolerant plants will do fine under a pine tree. Adapting your watering techniques to get water directly to the plants root system will increase their chance of survival. So the best plants for the area are ones that tolerate shade AND drought.
Some examples of good plants to plant under pine trees are:
#1. Creeping Mahonia: is a low spreading semi-evergreen. It will only get 18-24” tall but can spread up to 4’. The dark glossy foliage and nice texture contrast to the needles of an evergreen. In areas where they are receiving a little more sun the leaves will turn bright reed in the fall to add a brilliant pop of color. Small yellow flowers in the spring will give way to small attractive blue berries in the fall making this a true four season plant. The berries are sour but edible and will the birds will devour them. The one concern is that because this plant is semi-evergreen leaves can catch the dropping needles and will need to cleaned off occasionally.
#2 Aegopodium: also called Snow On The Mountain. This fast spreading herbaceous perennial is great for under pine trees. It grows quickly to around 18” tall but will spread to fill in almost any area. The slightly delicate variegated white and green leaves add a nice sense of contrast. When completely filled in Aegopodium creates a beautiful lush look. Because it is a perennial it will die back to the ground every winter but quickly regrow from the root system in the spring.
#3 Vinca Vine: Not to be confused with the annual Vinca flower, Vinca Vine is also often called Periwinkle and comes in two species: Vinca major and Vinca minor. They are a flat vine-like ground cover that can spread quickly. One plant by itself rarely gets more than a few inches tall but can reach as much as 3-4’ wide making a great and easy ground cover. Vinca comes in a few different varieties most with variegated leaves and large purple trumpet shaped flowers. Vinca major is faster growing and a bit more aggressive spreader than Vinca minor. It also has bigger leaves and flowers, BUT it is not as hardy or drought tolerant as Vinca minor and may not survive our colder winters.
#4 Lamium: also called Dead Nettle. Lamium is another fast growing mounding ground cover that can spread. Most varieties of Lamium have interesting small ruffled leaves that are variegated white and green. Unique flower clusters stand above the foliage and range in color from purples to pinks to white. One plant will densely mound to 12” tall and twice that wide. Lamium send out runners which may root and begin a new plant if allowed to sit on soil. To control spreading and maintain individual plants simply pinch off longer branches or surround the plant with rock or bark to prevent runners from rooting.
#5 Knickanick: Also called Bear Berry this extremely tough little broad leaf evergreen in another great example of a four-season plant. It makes a great ground cover because it grows very flat, only a few inches tall, but will spread up to 15’. It has small glossy green leaves that turn brilliant red with the onset of winter and will persist even through snow. Bear Berry sports small pink flowers in the spring that give way to bright red berries that critters love. It is extremely drought tolerant and cold hardy down to -50. Because it does tend to hold on to its leaves well and it is flat and woody needle clean up would be a must to prevent the plant from being smothered.