Pine trees represent a popular choice in the landscape thanks to their cheerful year-round greenery and fantastic ability to create a privacy barrier and windbreak. However, pine trees are also very competitive plants that make it tricky to fill in the surrounding area with shrubs or flowers.
For starters, a pine tree's canopy creates an intense shade that many plants cannot tolerate. Their extensive root system uses much of the available water. And although it's a myth that their fallen pine needles acidify the soil, pines simply thrive when growing on acidic soil and so must the plants around them. Therefore, keep three primary criteria in mind when hunting for plants or shrubs that grow well under pine trees: tolerant of full shade, dry soils and acidic soils. It's even better if a plant requires these growing conditions rather than simply tolerating them.
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Create a Blue-Tinged Shade Garden
If your pine tree has a bluish-green tinge, such as the Eastern white pine (Pinus strobus, USDA zones 3-8), consider complementing that unique color by planting shade-loving flowers with blue blooms. Try blue columbine (Aquilegia spp., zones 3-10) cultivars like 'Colorado Blue' or 'Rocky Mountain Blue.' The inner flower petals are white, but the star-shaped sepals come in anything from pale to bright blue.
Bigleaf hydrangea (Hydrangea macrophylla, zones 6-9) will produce blue flowers when grown on acidic soils, which can make them a good choice for planting under a pine tree. They are tolerant of shade, but you may want to give them a little extra water when planting them with a pine tree. Jacob's ladder (Polemonium caeruleum, zones 4-8) and dwarf periwinkle (Vinca minor, zones 4-9) represent other blue flowers that will grow well under a pine tree thanks to their tolerance for shade and acidic soil.
Simple Groundcovers for Pine Trees
If you'd rather plant just one type of plant and then take a hands-off approach, you'd probably appreciate a groundcover. Fast-spreading, low-lying plants like creeping thyme (Thymus serpyllum, zones 4-9) or creeping phlox (Phlox stolonifera, zones 5-8, or Phlox subulata, zones 3-9) will turn the barren area under a pine tree into a visually appealing but simple garden. Even when these groundcovers aren't in bloom, their stems and leaves provide an interesting texture opposite the spiny branches of the pine tree.
Other groundcovers suitable for planting under a pine tree include bearberry (Arctostaphylos uva-ursi, zones 3-7), creeping wintergreen (Gaultheria procumbens, zones 3-7) and sweet woodruff (Galium odoratum, zones 4-8). If you can be patient and don't mind putting in a little work, you can also manually spread hostas (Hosta spp., zones 3-8), ferns and other shade-loving plants until they fill in the entire area under a pine tree over the course of several years.
Full Shade and Acidic Soil
Shade gardens do not necessarily bloom as brilliantly or for as long as full-sun gardens, but you can still create a beautiful composition by focusing on the leaves' colors and textures. For example, hostas come in a variety of colors and patterns, as do ferns and coral bells. Consider astilbe (Astilbe spp., zones 4-9), rhododendron (Azalea spp., zones 4-9 depending on species and cultivar) or bleeding hearts (Lamprocapnos spectabilis, zones 3-9) to fill in the space under your pine tree.
Combine these shrubs with a groundcover for even more attractive results. You can also select plants with different bloom times to ensure there's always a burst of color under your pine tree.