Garden Care Guide

Black Walnut Care

Juglans nigra

A large tree that is toxic (allelopathic) to many plant species because of a chemical called juglone released from its roots, leaves and fruits. Therefore it should not be planted near sensitive plants such as tomatoes, apples and azaleas; it likes deep, moist and well-drained soils.

Hardy · -25 °C / -13 °F

Monthly care calendar

Timings are for a temperate Northern Hemisphere climate. In warmer areas tasks start earlier, in colder areas later; in the Southern Hemisphere shift them by six months.

January
  • Pests & diseases: Carry out general observation. Frost protection is not needed; it is very hardy.
February
  • Pruning: While the tree is in full dormancy, perform structural pruning on young trees to establish a strong central leader and select the main scaffold branches. On mature trees, only remove dead, diseased or crossing branches.
  • General care: Clear weeds.
March
  • Watering: If there is no rainfall, water deeply every 2 weeks (30-40 L/tree).
  • Fertilizing: Apply a balanced fertilizer or well-rotted organic fertilizer once when it wakes from dormancy.
  • Plant protection: If symptoms spread and treatment is needed, consult a licensed plant-protection supplier or an agronomist. Plant protection products are regulated; follow local rules.
  • General care: The buds begin to burst.
  • Pests & diseases: During humid and cool periods, monitor the leaves and trunk for signs of mold, spots and rot.
April
  • Watering: If there is no rainfall, water every 15 days.
  • Plant protection: If symptoms spread and treatment is needed, consult a licensed plant-protection supplier or an agronomist. Plant protection products are regulated; follow local rules.
  • General care: The leaves open fully.
  • Pests & diseases: Look for aphids (green or black clusters of small insects) on fresh shoot tips. If there are only a few, you can knock them off with a strong jet of water.
May
  • Watering: If there is no rainfall, water once a week.
  • Plant protection: If symptoms spread and treatment is needed, consult a licensed plant-protection supplier or an agronomist. Plant protection products are regulated; follow local rules.
  • General care: Spread a 5-7 cm layer of mulch over the root zone; it retains soil moisture and suppresses weeds. Do not pile mulch against the trunk.
  • Pests & diseases: Look for aphids (green or black clusters of small insects) on fresh shoot tips. If there are only a few, you can knock them off with a strong jet of water.
June
  • Watering: Water deeply twice a week; prefer infrequent and generous watering over small and frequent. The root zone should be wetted to a depth of 30-40 cm.
  • Pruning: Do shaping and hedge pruning.
  • Plant protection: If symptoms spread and treatment is needed, consult a licensed plant-protection supplier or an agronomist. Plant protection products are regulated; follow local rules.
  • Pests & diseases: Look for aphids (green or black clusters of small insects) on fresh shoot tips. If there are only a few, you can knock them off with a strong jet of water.
July
  • Watering: Water deeply twice a week; prefer infrequent and generous watering over small and frequent. The root zone should be wetted to a depth of 30-40 cm.
  • General care: Deep watering strengthens the root system.
  • Pests & diseases: Watch for signs of water stress (leaf yellowing, drop).
August
  • Watering: Water deeply twice a week; prefer infrequent and generous watering over small and frequent. The root zone should be wetted to a depth of 30-40 cm.
  • General care: Walnuts continue to ripen.
September
  • Watering: If there is no rainfall, water once a week.
  • Pruning: Do the last formative pruning of the season; do not let it put out new shoots before frost.
  • General care: Collect the walnuts that have fallen to the ground. Remember that their husks will leave stains.
October
  • Watering: If there is no rainfall, water every 15 days.
  • Plant protection: If symptoms spread and treatment is needed, consult a licensed plant-protection supplier or an agronomist. Plant protection products are regulated; follow local rules.
  • General care: Complete the walnut harvest. Leaf drop begins.
  • Pests & diseases: During humid and cool periods, monitor the leaves and trunk for signs of mold, spots and rot.
November
  • Watering: Not required, natural rainfall is sufficient.
  • Plant protection: If symptoms spread and treatment is needed, consult a licensed plant-protection supplier or an agronomist. Plant protection products are regulated; follow local rules.
  • General care: Collect fallen leaves; many disease agents and pests overwinter under leaves.
  • Pests & diseases: During humid and cool periods, monitor the leaves and trunk for signs of mold, spots and rot.
December
  • General care: The tree goes fully dormant.
  • Pests & diseases: Check the trunk and branches.

The care advice on this page is general and for information only; it is not professional advice. Plant age, soil and your garden’s microclimate can change the outcome. Plant protection products are mentioned only as general information; they are regulated, and the choice, dose and timing must be decided by a qualified professional under local rules. Consult a landscape architect or agronomist before applying.

Want reminders for every plant in your garden? Our garden-care app with monthly task lists and frost alerts is currently available in Turkish; the English version is on the way.

Browse all plant guides