Winters with alternating freezes and thaws are bad for roots, but on the bright side, they improve the structure of soil. (Barbara Damrosch)

April’s here, and, weather-wise, anything can happen. Northerners know better than to put away their snow shovels, and even a Mid-Atlantic gardener might think twice about putting all the tomato plants in the ground, springlike though it may be. Snow or frost may still appear.

Gardeners tend to be philosophical about weather events, partly because they’re beyond our control and partly because there’s usually an upside to them.

Snow is a case in point. To a cold-climate gardener, a consistent snow cover that lasts all winter is nature’s mulch. It protects any perennial plant hardy enough to take the cold, without the heaving and breakage of plant roots that comes with alternating freezes and thaws. On the other hand, freezing and thawing is great for the soil’s structure, opening up crevices that absorb water, nutrients and air.

Snow is also referred to by old-timers as the poor man’s fertilizer. That’s because snow and rain absorb nitrogen from the atmosphere and carry it to earth, adding as much as 10 pounds per acre in a form (nitrates) that plants can use.

Snow does it better than rain, because it seeps slowly into the soil rather than washing away as runoff.

Unfortunately, air pollution now adds way more acidic nitrates to precipitation than before, leading to algae blooms, damage to animals and plants, and other woes. So while a storm might make the air seem fresh and cleansed, it may have brought some trouble with it at ground level.

An excess of water, whether from heavy rain or rapid snowmelt, can be good or bad depending on how your ecosystem is managed. Flooding can lead to the loss of precious soil if a gardener leaves it exposed, without the protection of nature’s catchment system of plant roots. In ancient Egypt, the annual flooding of the River Nile was so beneficial to the fertile lands on either side that the river was believed to embody the god Osiris. It’s all about giving water a right place to go.

Wind is another great force in which nature giveth and taketh away. It’s annoying when it drifts snow onto the driveway, knocks over the corn or rips the row covers off the broccoli. But a windy night lessens the chance of frost. A windy day makes it harder for mosquitoes to fly.

If you live by the ocean, sea breezes not only cool and refresh, but they also carry a bit of the ocean with them. Seawater, in the form of windblown spray, delivers a healthy dose of trace elements that make garden plants thrive. No wonder seaweed fertilizers are so effective.

We all know by now that fire, despite the destruction it can cause when it runs wild, has its benefits, too. Fires caused by lightning (as opposed to campfires and tossed cigarettes) are part of a forest’s natural cycle, in which too much brush and too much dry tinder is cleared out, giving what plants remain a healthier life. The layer of burned foliage adds nutrients to the soil. Open clearings in a wooded area increase diversity and sustain plants and animals that don’t thrive in shade. A number of species will grow only after a fire, when their seeds are released by the extreme heat. All this renewal supports a greater diversity of animal life as well.

The sun, which drives the engine of life as our planet circles it in space, would get a 100 percent approval rating if it weren’t for sunburn, skin cancer and environmental crimes traceable to ozone-depleting chemicals used in modern life. Like Osiris, the sun was a god to the ancient Egyptians, who called him Ra.

But what about tornadoes? There is no tornado god I know of, though a large number of sports teams have adopted them as mascots. The best you can say about them is that they renew the landscape by ripping it to pieces. That they sometimes pick up seeds and resow them in another county. That they are amazing, monstrous whirling towers of terrifying force, and we have no business asking any favors of them because nature is in charge, and all they owe us is a reminder of that.

Tip of the Week

Dandelions and common blue violets announce their presence with flowers in early April: Both hold tenaciously to the ground but can be efficiently removed without pesticides with a fish-tail weeder.

— Adrian Higgins