Garden Care Guide

Black Locust Care

Robinia pseudoacacia

A fast-growing, drought-tolerant tree extremely well adapted to poor and dry soils. It tends to spread quickly by root suckers and produces fragrant flowers valuable to honey bees.

Hardy · -35 °C / -31 °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
  • Fertilizing: Not done; it produces its own nitrogen.
  • Pruning: The best time for structural pruning, clearing dead branches and especially cutting the root suckers that spread around.
  • General care: Keeping its spreading nature under control is the main cultural care.
  • Pests & diseases: Holes and sawdust piles in the trunk indicate damage by locust borer.
February
  • Pruning: Complete pruning and removal of root suckers by the end of the month.
  • General care: A suitable month for new plantings (but think carefully about its spreading nature before planting).
  • Frost risk: Protect newly planted seedlings from severe frosts.
March
  • Watering: Water a newly planted specimen more often than established plants during its first year, as its root system is still shallow.
  • 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: Good time for planting and transplanting.
  • Pests & diseases: Check the branches and trunk for brown, fixed bumps (scale insects).
April
  • Watering: Water a newly planted specimen more often than established plants during its first year, as its root system is still shallow.
  • 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: Good time for planting and transplanting.
  • 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
  • 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: Flowering begins. Drainage is vital for this plant. In heavy soil that holds water, plant it on a raised mound or berm 20-30 cm high, so the root collar stays above the surrounding soil level.
  • Pests & diseases: Check fresh shoot tips for aphids (small clusters of green or black insects). If there are few, you can knock them off with a strong spray of water. Check branches and stems for brown, stationary bumps (scale insects).
June
  • Watering: In a long drought, water deeply once a month.
  • Pruning: Do shaping and hedge pruning. Pruning in early spring increases the risk of bacterial wetwood disease; August-September pruning is preferred. Root suckers are invasive; keep them under control. Use protective gloves on thorny young branches.
  • 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: Flowering continues.
  • 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: In midsummer, deep watering every 15-20 days is enough. Established plants (over 2 years old) do not need watering in most years. The root zone should be wetted to a depth of 30-40 cm.
  • General care: Continue removing root suckers.
  • Pests & diseases: Check the trunk for woodpecker damage.
August
  • Watering: In midsummer, deep watering every 15-20 days is enough. Established plants (over 2 years old) do not need watering in most years. The root zone should be wetted to a depth of 30-40 cm.
  • General care: Continue removing root suckers.
  • Pests & diseases: Check the trunk for woodpecker damage.
September
  • Watering: In a long drought, water deeply once a month.
  • Pruning: Do the last formative pruning of the season; do not let it put out new shoots before frost.
  • General care: Seed pods form and may remain on the tree throughout winter.
  • Pests & diseases: Carry out a general health check.
October
  • Watering: Water a newly planted specimen more often than established plants during its first year, as its root system is still shallow.
  • General care: Good time for planting and transplanting.
November
  • Watering: Water a newly planted specimen more often than established plants during its first year, as its root system is still shallow.
  • General care: Suitable period for planting and transplanting. Make sure water does not pool in the root zone during winter rains; for this plant, drainage is more critical than irrigation. Collect fallen leaves; many disease agents and pests overwinter under them.
  • Frost risk: Protect newly planted seedlings during the first winter.
December
  • Pruning: You can start winter pruning and removing root suckers.

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.

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