Planting shrubs under trees works best when you dig between the big roots, set the plant level with the ground, and water it deeply for the first year. Your spade hits a web of roots the second it goes in under a mature tree, so you adjust your whole approach instead of forcing the hole. Find a gap, plant small, and keep that new root ball wet while it settles in.
That tangle of roots is the real challenge with shrubs under trees. Probe around with a hand trowel or a thin stake before you commit to a spot. When you feel a thick root, move over a few inches and try again until you find soft ground. You want a wide, shallow hole between the large roots, not a deep pit that forces you to chop through them.
Never cut a major tree root to make room. Those big roots hold the tree up and carry most of its water, so cutting one can hurt the tree and even make it unstable in wind. Slice through a few thin feeder roots if you must, but leave anything thicker than your finger alone. Work around it and pick a smaller shrub that fits the gap you found.
Established tree roots fight hard for every drop of water, and that competition is what kills most new shrubs in this spot. The tree drinks first and leaves your shrub thirsty. So you water deeply and often during that first season, soaking enough to wet the top 3 to 4 inches (about 10 cm) of soil each time. A quick splash from the hose runs off before it ever reaches the roots that need it.
Probe the soil to locate space between large roots and dig a wide, shallow hole there instead of cutting roots.
Place the root ball so its top sits level with the surrounding ground, never buried deeper than it grew in the pot.
Refill with native soil, firm gently, then water to wet the top 3 to 4 inches (about 10 cm) of soil.
Add a mulch ring kept off the stems and keep watering deeply whenever that top layer dries the first year.
Pick a shrub that already shrugs off dry shade and you cut your work in half. Aucuba brings bold spotted leaves and handles deep shade with ease. Oregon grape holly gives you spiny evergreen foliage, yellow spring flowers, and blue berries the birds love. Sweet box stays low and green and fills the winter air with scent. All three take the dry, dim ground under a canopy far better than a thirsty hydrangea ever will.
Set the root ball so its top sits level with the soil, never deeper than it grew in the pot. Burying the crown invites rot and slow death. Backfill with the native soil you dug out, firm it gently with your hands to close air pockets, then soak the whole area. Deep, infrequent watering beats a daily sprinkle. It pushes roots down to find moisture and keeps them strong, not shallow and weak.
Finish with a mulch ring around the new shrub, spread two to three inches thick but pulled back so it never touches the stems. Mulch piled against the bark traps damp and rots the base. The ring locks in moisture, blocks weeds, and softens the harsh competition you face when planting in tree roots. Keep checking that top layer of soil through the first year, and soak it again whenever it dries out.
Read the full article: Shade Loving Shrubs: 8 Best Picks
