The month of April kicked off with severe storms soaking much of the country. The old adage would have us believe that all this rain bodes well for next month's blossoms. But do April showers really bring May flowers?
No more so than showers in May or September. Exactly which rainy period has the biggest effect on growth depends on whether you're looking at perennials or annuals. Perennials, which are plants whose roots stay alive even after the part aboveground dies, usually pop up as the first proud trumpeters of spring. If you're in Maine or England, that's likely to be in May; farther south, it makes more sense to call them late-March and early-April flowers. (Some perennials like the Cyclamen coum have the audacity to show up and thrive as early as January.)
Regardless of when the perennials bloom, the rainfall of the previous month isn't that relevant. Plants such as tulips and daffodils, two common perennials, sprout from bulbs that have been in the ground since at least the previous autumn, which is when their buds were forming and roots were growing. So if there had been a severe drought in September, the tulips and daffodils may suffer months later. Once the foliage starts peeking through the soil in early spring, rainfall again becomes important. If there's a drought, the perennials won't grow as high, and they wither faster. But in most years, there's enough moisture in the soil from the winter's snow to sustain the spring flowers.
Whatever effect April's showers do have on May flowers tends to be negative. Too much rain while the plants are blossoming makes them more susceptible to diseases like Botrytis blight, which causes buds to shrivel before they open.
For annuals, which are the flowers that must be replanted every year, lifespan and growth are influenced by the rainfall in the months immediately after they're planted, not the month before. Summer annuals like petunias, marigolds, geraniums, tomatoes, and cucumbers go into the ground after the frost-free date, which varies by region but hovers around late April. Once planted, they must receive enough water during the next few months to stay healthy. (The exact amount depends on heat and wind, but a good rule of thumb is that if you stick a finger into the soil and feel some moisture, you're good.) Too much heavy rain can beat them down or, if the soil isn't draining properly, drown their roots and kill them. But April showers would have no effect on annuals planted in May.
The one place where April showers would truly bring May flowers is the desert. In arid regions like the Mojave, plants sit under the sand, sometimes for years, just waiting for enough water to send up shoots and leaves. A few weeks—or sometimes even days—after a heavy rainfall, the desert will explode with color.
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Explainer thanks Charlie Nardozzi of the National Gardening Association, Phil Normandy of Brookside Gardens, Jody Payne of the New York Botanical Gardens, and Thomas C. Vogelmann of University of Vermont.