Planting perennials under trees solves two problems at once: it turns that awkward, bare, shady spot into a lush garden layer, and it reduces the need for mowing or mulching around tree roots. The key is choosing tough, shade-loving plants that can compete with tree roots for water and nutrients, and planting them without damaging the tree. This guide walks you through selecting, planting, and caring for perennials under trees, with practical tips for success.
What You’ll Need
- Shade-tolerant perennial plants (choose varieties suited to your hardiness zone)
- Compost or aged leaf mold
- Garden trowel or small spade
- Watering can or hose with a gentle spray nozzle
- Mulch (shredded bark, wood chips, or leaves)
- Gardening gloves
- Optional: landscape fabric or cardboard for weed suppression
Step-by-Step
- Assess the conditions. Note how much sunlight the area actually receives. Under a dense canopy, you may have full shade; under a high-branched tree, you might get dappled or partial shade. Also check soil moisture – tree roots often dry out the soil quickly. Choose plants that match these conditions.
- Choose the right perennials. Opt for species that naturally grow in woodland settings. Good choices include hostas, ferns (like lady fern or Christmas fern), bleeding heart, brunnera, wild ginger, and foamflower. For a pop of color, consider astilbe or coral bells. Avoid shallow-rooted, sun-loving plants like lavender or sedum.
- Water the area a day before planting. This softens the soil and reduces stress on the plants. If the soil is bone dry, give it a deep soak the evening before.
- Dig planting holes, not a big trench. Use a trowel to dig individual holes between the tree’s major roots. Place each hole slightly wider than the plant’s root ball but no deeper. Avoid cutting any root larger than your thumb – that can harm the tree.
- Mix compost with the excavated soil. For each hole, combine a handful of compost with the soil you removed. This adds nutrients without disturbing the tree roots.
- Plant your perennials. Gently loosen the root ball, place the plant in the hole, and backfill with the amended soil. Firm the soil lightly around the base. The crown (where stems meet roots) should be level with the surrounding soil – not buried deeper.
- Water thoroughly. After planting, water each plant deeply to settle the soil and eliminate air pockets. Keep the area consistently moist for the first few weeks until roots establish.
- Apply a thin layer of mulch. Spread 2-3 inches of mulch over the planting area, but keep it a few inches away from the tree trunk and plant stems to prevent rot. Mulch helps retain moisture and suppress weeds.
- Maintain regularly. Water during dry spells for the first year. In spring, add a light layer of compost or a balanced slow-release fertilizer. Remove fallen leaves in autumn if they smother the plants, but otherwise let them decompose naturally.
Common Mistakes
- Planting too deep. Burying the crown leads to rot and plant death. Always keep the crown at soil level.
- Cutting major tree roots. Digging a large bed under a tree can sever important roots, weakening or killing the tree. Always plant in individual holes between roots.
- Choosing sun-loving plants. They will stretch, fail to bloom, and eventually decline in shade.
- Over-mulching. Piling mulch against the tree trunk traps moisture and encourages pests and disease. Keep it thin and pulled back.
- Ignoring soil compaction. Walking on wet soil compacts it, harming tree roots. Use stepping stones or avoid heavy foot traffic.
Tips
- Start with a small number of plants and expand gradually. This reduces disturbance to the tree and lets you see what thrives.
- Group plants with similar water needs together. Most woodland perennials prefer consistent moisture, but some, like wild ginger, tolerate drier conditions once established.
- Use a soaker hose or drip irrigation to water deeply and slowly, encouraging deep root growth.
- In very dry shade, choose drought-tolerant perennials like barrenwort (epimedium) or lungwort (pulmonaria).
- Add spring bulbs like daffodils or snowdrops for early color – they bloom before tree leaves fully emerge.
- If tree roots are too dense to dig, consider planting in raised containers or building a shallow raised bed with a fabric bottom, but be aware this may stress the tree.
Troubleshooting
- Plants are wilting despite watering. This may indicate root competition. Water more deeply and less frequently to encourage the perennials to send roots deeper. Also check for voles or other pests.
- Leaves are yellowing. Could be overwatering, poor drainage, or nutrient deficiency. Ensure the soil isn’t waterlogged; if it is, improve drainage by planting in raised mounds. If it’s nutrient deficiency, add compost or a balanced fertilizer.
- Plants are leggy and sparse. This usually means too much shade. Consider thinning the tree canopy slightly (prune lower branches) to let in more light, or replace with even more shade-tolerant species.
- Mulch is attracting ants or other insects. Keep mulch thin and away from stems. If ants are nesting, they are usually harmless, but you can rake the mulch to disrupt their colony.
- Tree roots are surfacing. Do not cut them. Add a layer of soil and mulch over the roots, and choose shallow-rooted perennials that can coexist.
Frequently Asked Questions
Q: Can I plant anything under a walnut tree?
Walnut trees release juglone, a chemical that inhibits many plants. Choose juglone-tolerant species like hostas, ferns, and most wildflowers. Avoid tomatoes, peppers, and other sensitive plants.
Q: How close to the trunk can I plant?
Keep at least a foot away from the trunk to avoid damaging the bark and major roots. The critical root zone extends well beyond the canopy, but planting in small holes anywhere under the canopy is generally safe if you avoid large roots.
Q: Will perennials harm the tree?
If you plant carefully in small holes and avoid cutting large roots, perennials are unlikely to harm the tree. They may compete for water, but with proper watering, both can thrive.
Q: What if the soil is full of roots?
If you can’t dig without hitting many roots, try planting in containers or raised beds with a barrier. Alternatively, choose groundcovers that can be planted by pressing small plugs into the soil without deep digging.
Q: When is the best time to plant?
Early spring or early fall are ideal, as temperatures are cooler and rainfall is usually more consistent. Avoid planting during hot, dry summer months unless you can water regularly.
Q: Do I need to fertilize?
Most woodland perennials are light feeders. A topdressing of compost each spring is usually sufficient. Avoid high-nitrogen fertilizers, which can promote leafy growth at the expense of flowers and may harm the tree.