When the temperature starts to drop….protect your plants!

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Fine Living: Shield your plants from winter’s chill
By PJ Bremier
IJ correspondent
Marin IJ

Posted:   01/12/2013 06:30:00 AM PST

MARIN’S FAMOUSLY gorgeous weather took a dip into the frost zone, which prompted Sloat Garden Center to issue one of its rare email alerts to gardeners on its mailing list.

“We only sent one out last year and that was in November when temperatures went down to the 20s after a really hot spell,” explains Katy Thompson, the green goods coordinator for Sloat. “We do it because people aren’t always thinking about the freeze protection, and the plants they love — their hanging baskets, their special begonias, their cymbidium orchid — are doing OK. But, all of a sudden, it’s 25 degrees outside, and the plants they love are dead.”

The first line of defense is keeping your plants well-watered a day or two before an expected frost, she says, especially citrus, tender perennials and subtropicals such as banana trees, fuchsias, hibiscus, bougainvillea, brugsmansia or anything from South America.

Like poinsettias, for example?

“Well, actually, some people put those outside intentionally,” she says with a laugh. “That’s how to get rid of them without feeling guilty!”

Moisture is key, she says.

“We’ve had a lot of rain this season but when it turns dry in the winter, the water evaporates and is used up quickly by the plant,” she says. “When a leaf doesn’t get water, it gets dried up like up just like our lips get chapped. Keeping the soil hydrated is important, especially for plants in containers.”

Gardeners can take further protections by using several products on the market, including Cloud Cover, an anti-transpirant, that comes in either ready-to-use ($13 a quart) or concentrated ($17 a quart) formulas.

“Cloud Cover is a spray-on polymer that coats the pores of the leaves so they don’t lose moisture but doesn’t prevent the plant from breathing,” Thompson explains. “The majority of frost falls on the top of plants — that’s where you’ll see the most damage — and that’s where you want to do the most protection.”

A ready-to-use quart should give full coverage to two to three average-sized garden plants. It should be applied after watering and a day before the frost sets in.

“You don’t have to spray it every day for it to be effective,” she says. “You’ll only have to reapply it after sufficient rains.

Other protective measures include N-Sulate Frost Protection Blanket ($17 for a 6-foot square) or Easy Gardener Frost Protection Bag ($15 for a 40-by-45-inch size).

“The heat from the soil escapes at night so blankets and bags trap warmth and as the heat rises from the earth they act as an insulating cover, like a comforter on a bed,” she says. “They can increase the air temperature around a plant by 2 to 3 degrees.”

Blankets are suitable for large plants or accessible trees, but they must be clipped on the plants so the cover doesn’t blow away. Thompson suggests potato chip bag clips or office binder clips. Bags work well for smaller plants and containers.

“They are just like the gauzy fabric of the blanket but they’re like a giant sock with a drawstring on the bottom so they won’t blow away if a wind comes up,” she points out.

She also suggests burlap totes, which cost about $6 for an 80-inch square.

“They’re old school but they’re very useful,” she says. “You can also use them just like a sack to carry leaves from the garden to the Dumpster or composter.”

She has a word of warning for gardeners who cover plants with plastic bags.

“Don’t let them actually touch the plant,” she cautions. “They need some support, like stakes, to prevent them from touching the foliage. The plastic can absorb the air and make it even cooler.”

And, if any plant is damaged by frost, don’t prune it now.

“Once the sun warms up, you’ll see the tips of plants turn black or brown and the temptation is to go and clean everything up,” she says. “If you do that, and another frost hits, you’ll damage it more. Wait until all danger of frost is gone and until new leaves emerge to prune it.”

So, which techniques does Thompson use in her cold Novato garden?

“My brugsmansia is old enough and comes back every year so I don’t worry about it and, except for my 12-year-old Owari Satsuma and my son’s project plants that I put inside my greenhouse, I let things die. It gives me a hole to plant something new.”

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