Winter jasmine fully abloom. (Adrian Higgins/The Washington Post)

The extreme El Niño winter has got even non-gardeners talking about plants, which is a sign of its conspicuous nature, so to speak.

One of the most grotesque responses to temperatures that climbed into the 70s recently is the elongation of ornamental cabbages, which are only remotely ornamental if they stay hunkered down in the cold. With the sort of consistently balmy days Washington has had recently, the cabbages have stretched to a foot or so on their way to opening up and producing flower stalks. In full bloom, they look interesting, even pretty, but it is the stages in between that are deeply worrying.

Now halfway stretched, they could subject themselves to the full force of single-digit temperatures, should they ever come, and in a late-winter thaw they will either rot or turn brown. In other words, ornamental cabbages have already passed their prime.

Many people think spring has arrived already with the cherry blossoms. This is because they are seeing a cherry tree designed to flower sporadically during mild spells in autumn and winter before a final flush in March. However many times you point out that this is the autumn-flowering cherry (Prunus subhirtella var. Autumnalis), folks just want to believe that Washington’s famous cherry trees are flowering and, thus, April will be all played out.

Ornamental cabbages stretch in the heat in downtown D.C. (Adrian Higgins/The Washington Post)

This is not to say that the precocious full flowering of this cherry tree and other plants in the garden is not unusual and unsettling. It is. For the gardener, much of December has been like living in the Gulf Stream-bathed gardens of the western British Isles, with winter jasmine fully abloom and the snowdrops up and nodding. The difficulty is that we aren’t in West Cork, and if and when Washington’s winter reverts to some normalcy, plants will be harmed by their half-hearted hibernation.

It was another prunus tree that I was wondering about — the Japanese apricot or Prunus mume — because this is the first real proto-spring prunus to flower, normally blooming in late February or early March. I called Scott Aker at the National Arboretum.

One early variety had already done its thing, its blooms were fading, he said. Another, a rose-red, double-flowered variety named Matsubara Red, “is going to be done here in a week, and the others in succession if we continue this warmth,” he said.

A less conspicuous woody plant named fragrant wintersweet is in full bloom, cloyingly sweet and about six weeks early for these parts. In my garden, nigella seedlings that usually sit out the winter at an inch or so are up to about nine inches in parts. They look vulnerable.

Apart from setting up the risk of freeze damage, all this mildness has less obvious effects. Aker pointed out that certain spring-flowering beauties — peonies, lilacs and irises — want a long bone-chilling spell to do their best at blossom time. “They’ll still grow and bloom, but if it stays mild they won’t be as spectacular,” he said.

Lettuce growing in the community garden. (Adrian Higgins/The Washington Post)

The orchard grower hankers for a deep, steady winter, not just to avoid blossom freezing in early spring but to give the apples, peaches and plums the chilling period they need for good bud development. “I think in the Shenandoah Valley they’re cold enough, but for the home orchard around here it could affect things,” Aker said.

It is not all gloomy: I have been harvesting fresh greens for weeks, not just hardy kale and collards for soups but mustard greens, tatsoi and arugula for salads. The more tender lettuce is just hitting its stride, thanks to row cover blankets on the couple of nights it dipped below freezing. Other lettuce growers in my community garden tell me theirs is already over the hill — bitter and preparing to bolt — but I sowed mine late, on Sept. 27, and it has yet to fully mature.

Another advantage of a mild winter is the chance to get all those maintenance jobs done that have been stacking up. For me, that is scraping away the top two or three inches of the earthen paths around the vegetable plots so I can add a fresh, thick layer of wood chips. At this time last year, the ground was unworkable, and didn’t thaw until early April.

More from Home and Garden:

What this mild autumn means for your plants

Why manicured lawns should become a thing of the past

The real forest that inspired the stories of Winnie-the-Pooh