When to water plants

Indicator plants shout out when they're thirsty and need water.

 Seasoned gardeners know which plants are quickest to show they want water — like the attention-needy third grader, waving a hand madly in the front row, yelling, “Call on me!”

When that plant signals, then everything gets watered. With winter coming on, and more houseplants tucked indoors, now is the time to think about which garden denizens are your indicators and how they tell you “Water me!”

The only difference between so-called “green thumbs” and “black thumbs” is the ability to pay attention to what plants are saying. Especially when it comes to their water needs.

My friend Debra Prinzing once described her lovely, but nongardening, husband as someone who could walk by a wilted plant stretched out on the ground, crawling like a thirsty man across desert sands. “And,” she says, “he won’t see it.”

Thanks for noticing.

So the first step is to pay attention. Lack of water shows up differently for various plants.

Some, such as my all-green spider plant, (Clorophytun comosum) turn their leaves to a grayish cast when faced with a water shortage.

Others, like Dracaena marginata, show their thirst by angling leaves downward first. Then, if not attended to, they simply support less foliage by dropping the excess.

My jade plant (Crassula ovata) tells me it’s thirsty by losing the shine on its succulent leaves. If I ignore it, each leaf becomes pitted like a pin cushion, as if it’s sucking in what moisture remains.

The shifting indicators
In general, large-leafed plants, or those with delicate foliage will be the first to shout out. Plants with gray-green, small leaves — or tough, hairy or succulent foliage — these are the stoics in the bunch.

However, other conditions can change the picture.

Plants newly arrived from a nursery are often grown in such light potting mix — not soil — that they can droop without additional water in half a day of strong heat.

Overcrowded roots in pots can also make a difference. For instance, on the patio my angel’s trumpets (Brugmansia ssp.) with their broad leafy foliage and abundant late-summer flowers are usually my indicator plants. When they hang their leaves straight down, I haul out the hose.

But this year brought a change. The night-scented jasmine (Cestrum nocturnum) now fully occupies its container. It might be rootbound. So even though it is a far tougher plant — some call it a weed in Los Angeles — and the leaves are considerably smaller than the angel’s trumpets, it wilts faster. This summer it moved up to No. 1 status as the indicator plant — where my eyes go first when I survey my garden.

Which plants are indicators in your garden? Which plants told you they were thirsty, but you didn’t listen? We all have stories about when we weren’t “plant whisperers” and the results end up in the compost. It’s not an accident that the words “ignore” and “ignorance” are so close. Indicator plants allow us to satisfy their thirst by pouring drinks at the right time.

Mary-Kate Mackey, co-author of “Sunset’s Secret Gardens — 153 Design Tips from the Pros” and contributor to the “Sunset Western Garden Book,” writes a monthly column for the Hartley Greenhouse webpage and numerous articles for Fine Gardening, Sunset, and other magazines. She teaches at the University of Oregon’s School of Journalism & Communication. She writes about water in the garden twice weekly for Diggin’ It. 

Editor’s note: Click here to read “How to overwinter tropical fruits and other tender plants.” To read more by Mary-Kate, check our blog archive. Gardening articles on a variety of topics can be found at the Monitor’s main gardening page. Also see our RSS feed. You may want to visit Gardening With the Monitor on Flickr. Take part in the discussions and get answers to your gardening questions. If you join the group (it’s free), you can upload your garden photos and enter our next contest.