Delaware Nature Guide: May 2026
May is the climax of the Delaware nature year — the globally significant gathering of Red Knots and shorebirds on the Delaware Bay shore as the horseshoe crabs spawn, peak songbird migration in the woods, and wildflowers and trees at their fullest. For naturalists, no month rivals it.
What to look for this week
- Tens of thousands of snow geese crowd the Bombay Hook impoundments, rising in roaring white clouds — the heart of Delaware's winter waterfowl spectacle.
- The Quadrantid meteor shower peaks in a short, sharp burst around January 3; watch the northeast after midnight from a dark Cape Henlopen or lower-Sussex site.
- A kitchen-table planning week — order seeds and sketch beds, leaving any snow banked over perennials as insulation against the coastal-plain freeze-thaw.
- American holly, the state tree, stands glossy and red-berried through the bare coastal-plain woods, the signature green of the Delaware winter.
Birds This Month
May is Delaware's greatest birding month and the site of one of the natural wonders of the Western Hemisphere. As horseshoe crabs swarm ashore on the Delaware Bay beaches to spawn around the new and full moons, hundreds of thousands of shorebirds gather to gorge on their billions of green eggs — most famously the red knot, a long-distance migrant that times its arrival to refuel here for the flight to the Arctic, alongside ruddy turnstones, sanderlings, semipalmated sandpipers, short-billed dowitchers, and dunlin. The spectacle peaks in mid-to-late May at beaches like Mispillion Harbor, Slaughter Beach, and Kitts Hummock.
Inland, the woods are at peak songbird migration: waves of warblers — black-throated blue, magnolia, Blackburnian, American redstart, prothonotary in the swamp woods — move through alongside scarlet tanagers, rose-breasted grosbeaks, Baltimore orioles, and indigo buntings. The marshes are loud with breeding willets, clapper rails, and marsh wrens.
This month's tip: visit Mispillion Harbor or the Delaware Bay beaches on a rising tide around the mid-May full moon to witness the red knot and horseshoe-crab spectacle from the designated viewing areas — and never disturb the feeding flocks, which depend on every minute of feeding.
What's Blooming
May is the lush peak of the Delaware flowering year. The later woodland wildflowers come into their own: wild geranium, Solomon's seal and false Solomon's seal, mayapple, jack-in-the-pulpit, wild columbine on the rocky Piedmont ledges, foamflower, golden ragwort, and the lingering Virginia bluebells and violets along the Brandywine and White Clay Creek. The native pink azalea pinxter flower and the white-flowered mountain laurel bloom in the moist acid woods.
On the coastal plain and along the shore, the season takes its own form: beach plum finishes its white bloom on the dunes, fringe tree drips white from the woodland edges, and the first blue flag iris and swamp rose open in the wet meadows and marsh edges. Meadows brighten with wild strawberry, fleabane, and the first blackberry bloom. It is the richest, greenest stretch of the Delaware year, the whole low state in leaf and flower.
Garden This Month
May is when the Delaware garden goes full warm-season. With the last frost past statewide, set out tomatoes, peppers, eggplant, and basil, and direct-sow the heat-lovers the long First State summer rewards: beans, lima beans, squash, cucumbers, melons, watermelons, and sweet corn. Keep succession-sowing beans, corn, and lettuce every couple of weeks for a continuous harvest, and set out sweet potato slips toward month's end as the soil fully warms. Plant out summer annual flowers and dahlia tubers.
Watch for a rare late cold snap and keep row cover handy, especially in the cooler north. Mulch beds to hold moisture and suppress the fast-germinating weeds, and stake or cage tomatoes at planting before they sprawl. Harvest the spring crops now hitting their peak — asparagus, peas, spinach, lettuce, and the first strawberries — and keep the cool-season beds picked before they bolt in the warming weather. Watch for the first cucumber beetles, squash bugs, and Colorado potato beetles, and stay ahead of slugs in the damp coastal-plain soil. It is the most rewarding planting month of the year.
Zone 7a (northern New Castle County): the last frost has passed by early May here in most years — set out tomatoes, peppers, eggplant, and basil, and direct-sow beans, squash, cucumbers, melons, and sweet corn, keeping row cover ready for a rare late cold night.
Zone 7b (Kent, Sussex, and the coast): the frost-free season is fully open — plant all the warm-season crops early in the month and begin succession-sowing beans, corn, and cucumbers, watching for the cool, damp nights the bay shore can still bring.
What's at the Farmers Market
May reopens Delaware's outdoor markets for the season — the Historic Lewes Farmers Market at George H.P. Smith Park, the Saturday market in Milton, the Wednesday Dover and Newark markets — just as the First State's signature spring fruit arrives. Local strawberries ripen by mid-to-late month from the u-pick fields of Sussex and Kent, where the Chandler and Flavorfest June-bearing varieties carry on the state's long strawberry heritage. Asparagus is at its abundant peak, and the stands fill with spinach, lettuces, radishes, scallions, green garlic, and the first sugar snap and English peas.
The coastal-plain warmth means Delaware also sees the season's earliest hoop-house tomatoes and cucumbers begin to trickle in late in the month, ahead of much of the Northeast. Bedding plants and vegetable starts crowd the grower tables as gardeners stock up, alongside Sussex honey, pastured eggs, and the first cut peonies and snapdragons. Pick strawberries fully red and fragrant and use them within a day or two, kept dry and refrigerated unwashed; choose asparagus with tight, compact tips and greens with crisp, unwilted leaves. The Delaware market is at its bright spring abundance, the first homegrown fruit of the year finally on the table.
Night Sky This Month
Mild May nights are prime for Delaware's small but dedicated stargazing scene. The darkest accessible skies in the First State lie at the southern Sussex parks — Trap Pond State Park, which hosts community star parties over its bald-cypress swamp, and Cape Henlopen State Park, where the Atlantic horizon opens the southeast away from the Wilmington and Dover glow. In the Piedmont north, the Delaware Astronomical Society runs public viewing nights at the Mount Cuba Astronomical Observatory near Greenville. At Delaware's latitude of roughly 39° N the spring sky rides high and well-placed for the whole evening.
The constellation roll-call is the familiar spring lineup: trace the Big Dipper's handle to orange Arcturus in Boötes and on to blue-white Spica in Virgo, while the keystone of Hercules climbs the east carrying the globular cluster M13 and Vega rises to lead the Summer Triangle. The Eta Aquariid meteor shower, debris from Halley's Comet, peaks in early May, favoring southern latitudes but still throwing swift meteors low in the southeast before dawn. With shortening nights, this is a quiet month for hunting the galaxies of Virgo and Coma Berenices overhead.
Exact planet positions vary year to year — the printable Delaware night-sky guide carries this year's details for your region.
Butterflies & Pollinators
May fills Delaware with butterflies. The big swallowtails are now on the wing in numbers — eastern tiger swallowtail, spicebush swallowtail, black swallowtail, and the zebra swallowtail in the south where its pawpaw host grows in the floodplain woods — nectaring at lilac, dame's rocket, and wild geranium. Spring azures, pearl crescents, American ladies, red admirals, common buckeyes, and the big silver-spotted skipper brighten gardens and meadows, and the moist woods host juvenal's duskywings and the brief-flying falcate orangetip.
Monarchs returning from the south arrive this month and begin laying eggs on milkweed across Delaware, and the first home-grown caterpillars appear by late May. The great spangled fritillary emerges in the meadows, its caterpillars having overwintered to feed on violets. Now is the time to set out nectar plants and protect milkweed, and to watch host plants for the eggs and tiny caterpillars of the season's first broods. The full warm-season butterfly fauna of the First State is on the wing.
Trees This Month
By May the Delaware forest is in full leaf, the canopy closed and deep green. The late-blooming trees flower now: tulip tree opens its big orange-banded green tulip-shaped blossoms high in the canopy, black locust drapes the roadsides in fragrant white chains, American holly, the state tree, sets its small white flowers along the coastal plain, and black cherry and fringe tree bloom. The shrub layer is spectacular — mountain laurel bursts into pink-and-white bloom in the moist acid woods, alongside highbush blueberry and the native azaleas.
In the Sussex County woods, the loblolly pines push new candles of growth, and the Atlantic white cedar and bald cypress of the swamps flush soft green. The oaks — white, willow, southern red, and black — have fully leafed and hang their catkins, dusting cars and ponds with pollen. The transformation from the bare gray woods of winter to the lush, shaded green of early summer is complete across the whole low state, and the first sweetgum and sycamore stand in full dense leaf along the rivers.
Go deeper with the Delaware guides
The complete Delaware birding, native-plant, wildflower, and night-sky guides — or the whole year in one bundle.
Same month elsewhere: May in Washington, D.C. · May in Florida · May in Georgia