These are the average bloom times for a typical year, 1998. Please be aware that blooming dates are very variable from year to year due to weather conditions.
Dumbarton Oaks in April - GardenRant
Patrick Dougherty — Dumbarton Oaks
Explore the Gardens — Dumbarton Oaks
Lilac Circle — Dumbarton Oaks
Hugh Livingston — Dumbarton Oaks
Dumbarton Oaks at Cherry Blossom Time
Bloom - CD
Bloom - CD
Fountain Terrace — Dumbarton Oaks
User's Guide to Dumbarton Oaks in the Spring
Blissing Out at Dumbarton Oaks