Recent overnight freezes brought a reminder that this is still winter, but the prevailing sentiment among my gardening buddies is that we are trapped in a sort of twilight zone autumn that never ended.

We know this to be wrong — the crocuses are up, the early daffodils, too, and the tree buds are dropping their protective scales — so we are gliding into spring. What we’ve experienced since the new year began is neither a late fall nor a precocious spring, but an unusually mild and snowless winter that has demonstrated the value of planting for winter effect.

The winter that never was remains an unsettling thing, but not to revel in its positive effects would be churlish. If you had in your garden such hibernal bloomers as hellebores, mahonias, sweetbox, Cyclamen coum, witch hazels, edgeworthia, daphnes, camellias, violas, autumn-flowering cherry trees and wintersweet, to name a few, you would have hit the jackpot in 2020. Although they are advanced, they are not precocious spring bloomers; they are plants that are programmed to flower in the winter but are usually stymied by the volatile weather of the Mid-Atlantic. This year, we didn’t see the grudging blossom sequence of a roller-coaster winter or the bloom-and-zap destruction of a sudden deep freeze or the fleeting flower-and-fizzle display of 70-degree days. No, it has been cool but mild, coaxing a long and measured display that began early and endures.

Nowhere is this better expressed than at Winterthur, the estate north of Wilmington, Del., whose garden and grounds were planted by its consummate plantsman owner, Henry Francis du Pont.

Its creator died a long time ago now — 1969 — but his spirit lives on in March Bank, named for its perch on the side of a stream valley and the month of its main show (normally). Amid towering columns of 150-year-old tulip trees and oaks, the woodland floor launches the growing season with tens of thousands of flowering bulbs first planted a century ago by du Pont and since increased by ­self-seeding.

He planned a sequence of late-winter, early-spring flowering effects heavily reliant on bulbs. The first to appear is the winter aconite, essentially a ground-hugging buttercup above lacy green foliage, followed by a perennial named adonis (here, an early variety, Fukujukai), with a showy, golden yellow bloom, bare at first but then supported by a growing, feathery tuft of foliage. Then the snowdrops pop, starting with the giant snowdrop and moving to the daintier common snowdrop. This chorus builds on itself until at the end of February and early March, the woodland floor is awash in pools of gold and white. Except this year, the show began in early February or before, and was peaking when I was there last week.

This is followed by March Bank’s even more popular progression, when this mix turns blue with the appearance of scilla (Alpine and Siberian) and glory-of-the-snow. “It’s like blue snow, three to four inches tall,” said Chris Strand, director of garden and estate. “It’s very surreal-looking.” As these beauties fade, they are succeeded by carpets of the Italian windflower. The estate opens to the public Feb. 29, though members have garden access year round.

Given the current trajectory of the weather, said garden curator Carol Long, the blue phase will probably start in a week or two and will last up to three weeks if the weather stays cool. Their lingering foliage offers a week or so of green respite — and then spring kicks in with effusions of dicentra, uvularias, bloodroot and trilliums, with some Italian windflowers and Virginia bluebells joining the party.

Less frenzied, the winter show is thrilling. This year, it seems unbeatable.

Linda Eirhart, director of horticulture, said that in the past 11 seasons, only two — 2012 and 2013 — matched this year’s earliness. In the other years, the current display was delayed as late as mid-March.

In 2007, I was viewing the snowdrops on March Bank when it started sleeting and then snowing until the nodding blossoms were blanketed in the stuff. The snowdrops were unaffected, but I barely made it home in one piece.

Most gardens planted a century or more ago, to the extent they survive, look as dated as a Model T Ford, but March Bank is a timeless evocation of the woodland idyll and is du Pont’s faithful replication of the type of romanticized garden scenes pushed by the Victorian tastemaker William Robinson.

The unmediated meeting of tiny late-winter bulbs and the pillars of giant trees on a panoramic scale is powerfully moving, but the effect is heightened by the knowledge that some of the plants are hard to establish and rare in commerce today, and that the scene before you takes decades to achieve.

Because they are seedlings, the snowdrops are full of quirky individual variation in petal size and display, as well as the markings of their inner petals.

Strand and Long lead me to the bank on the other side of the stream and to a large wooded pocket where a snowdrop relative named the spring snowflake is beginning to appear. The plant is a little taller than the snowdrop, the blooms bigger and more spherical. “This is starting to come in early,” Strand said. In a couple of weeks, “it will be like white marbles floating in the air.”

One of the reasons the bulbs thrive here is because the trees are so tall and the woodland floor is neither too bright nor too dark. Another is that they are not smothered by wood mulch. The gardeners simply shred the fallen leaves in fall.

On the lawn of the East Terrace, right by the mansion, sits three old tulip poplars and a beech tree. The lawn has the pale violet haze of thousands of Crocus tommasinianus, which is the earliest crocus to appear but is still three weeks early.

At March Bank, the weeks of bloom, and the sequencing of it, are a reminder that you can achieve astonishing effects with the tiniest of plants if you plant enough of them, in layers.

“I wonder if people had this type of garden,” Long said, “they would feel differently about winter.”

Tip of the Week

Electric heat mats, placed under seed trays, will speed the germination of vegetables and annuals and are recommended to coax slow germinators such as peppers and eggplants into life.

— Adrian Higgins

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