When it comes to watering, sometimes less is more

Here’s a test for garden sleuths: I recently visited a garden where a large planting of big root geranium (Geranium macrorrhizum) was pale and struggling and ambitious weeds were creeping into what should have been an effective groundcover. Big root geranium is a particularly adaptable plant, rarely in need of any kind of attention, so this was odd indeed.

Further investigation showed rock-hard ground and no sign of the watering system there working, but that wasn’t the real problem.

What I think happened was that this planting had been frequently and lightly watered since it had been planted several years ago — a well-meaning attempt to care for the plants that had unintended consequences. If my theory is correct, I think these plants never had to go looking for water and therefore never grew deep roots, so when the water system they relied on failed, the stress was obvious.

There’s nothing like a heat wave to get gardeners thinking about water, but as the example above shows, there’s more to watering than just waving the hose around the garden, and it’s worth keeping some best practices in mind. 

The first is that when a heat wave is coming, its good for new and sensitive plants to be well watered from the get-go to reduce plant stress. Established plants will also appreciate being hydrated but are far more tolerant of high temperatures. When there’s not a heat dome on the way, new plants will appreciate about an inch of water a week.

Maximizing watering efficiency is always important, but particularly so during high temperatures, and this means watering the soil rather than the plants when possible. This may seem antithetical since rain delivers water in the opposite way, but consider that “good” rain showers last for hours, and rain that hits foliage drips off to the ground. So unless you want to spend hours impersonating a rain shower, the place to point the hose is at the roots.

Soaker hoses and drip irrigation do an excellent job of efficiently delivering water to the roots of plants. I would not be able to grow vegetables if it weren’t for drip irrigation connected to automatic timers because I’d never be able to water as regularly as vegetables would like. Drip irrigation also comes in handy in a bed with a lot of annuals, but instead of using a timer, I simply connect a hose to the drip tubing when necessary — something I’ve done only a handful of times so far this year — rather than water regularly.

And the sprinkler is always at hand and often in use, primarily to help establish new grass in lawn patches but also to water large, newly planted areas. 

But perhaps the best rule of watering is to skip it sometimes. Perennials, shrubs and trees should be watered deeply and infrequently, which encourages plants to put down deep roots, allowing them to be self reliant once established (usually a year for perennials and two for shrubs and most trees). 

And those deep roots mean that when the next heat wave comes, at least you won’t have to worry about part of the garden.