How to save a half-dead plant

Summer vacations just complicate the problem; no one is around to make up for spotty or inadequate irrigation.

I was reminded of that this week the hard way. Before an extended trip, I had gathered several potted plants together; they usually were hand-watered along the edges of our patio. Instead, I positioned them in two rows so they would all be hit more or less equally by sprayers on a timer. It worked when I tested it. But upon our return, I discovered the plants (all mini roses) closest to the sprayers had grown – and blocked the spray from reaching some plants in the second row.

The first row of roses greeted me with new blooms; two in the second row looked extra crispy with brown leaves.

A similar situation hit my hydrangeas, notoriously thirsty shrubs. Some 6-foot cannas had fallen over and blocked the sprinklers that irrigate the hydrangea’s mixed bed; three bushes looked near death. (So much for those summer blooms.)

Such guilt-inducing summer scenes are common this July; even with fully functioning irrigation, gardens were stressed.

To start this month, Sacramento experienced eight consecutive triple-digit days. After a brief break Tuesday (in the mere high 90s), downtown Sacramento hit a record 113 on Thursday.

According to UC Cooperative Extension master gardeners, “Plants are injured if temperatures become too high in the canopy or root zone, dehydrating tissues and killing plant cells. Damage is more likely the longer plants are exposed to excess heat and if they are moisture stressed, otherwise unhealthy, young, or a species more susceptible to high temperatures.”

To save these heat victims, it’s time for green thumb triage.

First, check the soil moisture around the plant. If you can’t plunge a 6-inch screwdriver into the root zone, that plant is definitely suffering. Give it a long, slow, deep drink, allowing the water to seep in.

The rootball of extremely dehydrated container plants often contract, pulling away from the sides of the pot. The initial response is to fill the pot to the rim with water (and the hose blasting). But instead of moisturizing the roots, the water just shoots down the sides and out the bottom (if the drainage holes aren’t blocked).

To bring back those plants, pull it out of that pot and soak the whole rootball in water for at least a couple of hours or overnight (but not longer). Then, repot with fresh soil or potting mix. Put the plant in a shady spot, protected from afternoon sun, until it shows new growth.

With water, most plants will bounce back quickly. They likely will drop damaged or browned leaves; they’ll need some extra nitrogen to replace that foliage. Give them some well-aged compost mulch; that retains moisture while also slowly feeding the plant.

Without enough water in this triple-digit heat, tomato vines, squash plants and other summer staples may show some dieback. Foliage not only provides energy for the plant, it shades the plant’s fruit. Trimming off the dead leaves and deep-watering plants can prompt new growth, but remember to provide some temporary shade for those baby tomatoes and vegetables.

And don’t feed (fertilize) any plant until it has recovered; otherwise, it will just add to the plant’s stress.

For more information on heat injury to plants: https://ipm.ucanr.edu/PMG/GARDEN/ENVIRON/thermal.html.