Hostas thrive beneath the canopy of established trees, adding lush foliage to shady garden spaces. Planting them presents a challenge, as hostas must compete directly with the tree’s extensive root system for moisture and nutrients. Successfully establishing them requires specialized preparation and planting methods that minimize disturbance to the tree.
Site Assessment and Preparation
Start by assessing the area beneath the tree’s canopy to locate the density of surface roots. Trees like maples and locusts have shallow, invasive root systems that create intense competition, while oaks with deeper taproots may pose less of an issue. Do not attempt to dig deep holes or sever substantial tree roots, as this can severely damage the tree.
Instead of deep digging, create a slightly raised planting bed over the existing soil. Clear the area of debris and identify pockets of soil between the tree roots. Apply a layer of three to six inches of organic material, such as compost or aged manure. Spread this amended soil without burying the tree’s trunk flare, which can cause rot. This improves drainage and aeration for the hostas while avoiding damage to the tree’s structural roots.
Planting Techniques Near Tree Roots
Use a trowel or a small hand fork rather than a large shovel to minimize the risk of cutting into a major tree root. Dig a planting hole only as deep as the hosta’s root ball and twice as wide. Focus on finding existing soil pockets between the tree’s surface roots to place the plant.
Gently loosen the hosta’s root ball and spread it out horizontally, since hosta roots grow wide rather than deep. Place the hosta so the crown is level with the surrounding amended soil. Backfill the hole with the organic-rich mixture and tamp lightly to remove air pockets. This provides the hosta with a wide layer of soil for quick establishment without risking deep excavation.
Watering and Ongoing Maintenance
Hostas planted beneath trees must compete for water, making consistent moisture necessary for survival and growth. Immediately after planting, water thoroughly to settle the soil and reduce transplant shock.
For the first four to six weeks, newly planted hostas need frequent watering to establish their root systems, generally requiring a deep soak several times a week.
Once established, hostas require about one inch of water per week, often necessitating supplemental irrigation because the tree canopy intercepts rainfall. Deep, slow watering is most effective, promoting hosta root growth while discouraging the tree’s surface roots from invading the bed.
Apply a layer of two to three inches of organic mulch, such as shredded bark or compost, over the planting area to conserve moisture and suppress weeds. Keep the mulch a few inches away from the tree trunk and the hosta crowns to prevent rot.