Guide

Go seePlants

Lilac season at the Arnold Arboretum, with leashed dogs

May

The Arnold Arboretum holds one of the oldest and largest lilac collections in North America, and its grounds are open to dog walkers as long as every dog stays leashed. In May the lilacs come into bloom on Bussey Hill over the course of several weeks.

Why this time of year

The Arboretum says its lilacs reach peak bloom during New England's traditional lilac time, the second through the fourth week of May. A cold spring can push peak bloom later.

How to notice it

  1. Walk your leashed dog up toward Bussey Hill, where the lilac collection grows, and wander the paths between the shrubs.
  2. Compare the shrubs as you go: the collection holds many kinds of lilac, and the Arboretum says they bloom over the course of several weeks rather than all at once.
  3. Keep your dog leashed the whole visit and pick up after it; the Arboretum requires both.

Try this with kids: Smell three different lilacs. Which one smells the strongest? Use your nose, not your hands.

Safety

  • Arnold Arboretum: 'Leash your dog, as coyotes are known to view small dogs as potential food and large dogs as competition.'

Sources

  • arboretum.harvard.eduPRIMARY, Arnold Arboretum visitor tips and guidelines (read 2026-11-10, via WebFetch; direct curl returned 403). 'Dogs must be leashed at all times.' 'Owners are responsible for removal and disposal of their dogs' waste.'
  • arboretum.harvard.eduPRIMARY, Arnold Arboretum wildlife page (read 2026-11-10, via WebFetch). 'Please help protect the flora and fauna by leashing your dog.' 'Leash your dog, as coyotes are known to view small dogs as potential food and large dogs as competition.'
  • arboretum.harvard.eduPRIMARY, Arnold Arboretum lilacs page (read 2026-11-10, via WebFetch). 'The following lilacs reach peak bloom during New England's traditional lilac time-the second through the fourth week of May.' Collection is 'one of the oldest and largest in North America'. Hedgerows on 'the east side of what is now called the Explorers Garden on Bussey Hill.'
  • arboretum.harvard.eduPRIMARY, Arnold Arboretum story, May 9, 2020 (read 2026-11-10, via WebFetch). Lilacs 'will bloom as usual over the course of several weeks'; peak later than usual that year because of colder spring weather; lilacs 'coming into bloom on Bussey Hill.'

Checked against these sources on November 10, 2026.

In the guide for May

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