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What you can do to keep plants healthy during this early warm spell

A Peggy Clark ornamental Japanese apricot tree blooms at Botanica this week – two to three weeks early.
A Peggy Clark ornamental Japanese apricot tree blooms at Botanica this week – two to three weeks early. Courtesy photo

It wasn’t long ago we were bracing for the first freeze of winter.

But with a relatively warm season, we’re already holding our breath for the last freeze. As plants respond to relatively high temperatures, with no sign of frost in the forecast, spring flowers and summer fruits hang in the balance should a freeze come at the wrong time.

“This is the point where you start getting nervous,” extension agent Rebecca McMahon says of the early plant growth. “It’s either going to be like 2011 where we didn’t have a freeze after about March 4, or like 2007 where it’s warm early and things start growing, and then the first of April you get a devastating freeze. We’re waiting to see which version” we get in 2016.

People have been unsure about whether to prune rose bushes or treat weeds or stew over soaring tulip foliage.

While there’s nothing we can do to change the weather or slow plant growth, and we don’t want to do anything too soon when a chance of a freeze remains, we can help keep plants healthy by watering, according to Ward Upham of K-State. Watering will help plants weather any cold damage.

“When we do water, we need to water deeply so it goes down to the roots,” says master gardener and rose expert Norma Kemp. “And I think a lot of people are watering.”

Garden displays, yard accoutrements, plants anticipate season at Century II. (Video by Annie Calovich)

And after a mere  3/4 inch of precipitation so far this year, there is a chance of rain Saturday night through Wednesday night.

There’s plenty of time for Wichita to get a freeze, says meteorologist Eric Metzger of the National Weather Service in Wichita.

The earliest last spring frost (32 degrees or lower) recorded in Wichita was on March 10, 2012. The average date is April 11.

The earliest last freeze (28 or lower) was Feb. 20, 1905. The average date is March 29.

The main things to keep in mind are that any new growth on plants can be killed by a cold snap, including flowers that are in bud and any resulting fruit. The plants themselves usually aren’t killed, unless they’re already stressed. That’s where the watering can be of some help.

In 2007, a deep freeze right before Easter wiped out flowers and the peach and apple crops, required copious amounts of pruning of new growth that had gotten nipped, and even killed some trees and shrubs.

This year, people have been calling the master gardener hotline asking whether they should prune their rosebushes. Kemp is going to wait to prune hers.

I know some people want to go ahead and (prune roses), but should we have a frost, we’d have to cover them, and would it be enough to protect them?

rosarian Norma Kemp

“They’re leafing out, but I’m not going to do any pruning until, oh, toward the end of the month. Unless like some of your shrubs have some dead wood, you can always take that out,” Kemp says. “I know some people want to go ahead and do it, but should we have a frost, we’d have to cover them, and would it be enough to protect them?”

Since the weather has been so warm, one light frost won’t do much damage, Metzger says.

“What really hurts a plant is a hard freeze, when you get the ground frozen,” he says. “And when it’s as warm as it has been, it’s going to take more than one morning, a few hours at 32 to do that.”

You might keep a light sheet or a row cover purchased from a garden center to throw over sensitive plants or those in bud should temperatures be forecast to fall to 28 or below for multiple nights. The foliage of spring-flowering bulbs or cold-hardy vegetables won’t be harmed by the cold.

But if you have acres of bulbs, as they do at Botanica and Bartlett Arboretum in Belle Plaine, and the bulbs are in bud, the stakes are a little higher, and covers don’t come that big.

We’re turning on the irrigation early.

Robin Macy of Bartlett Arboretum

“We’re turning on the irrigation early,” Robin Macy says of the arboretum. “We are prayerful, and we know that spring’s going to be early, and we’re getting ready for that.”

The first scheduled event of the spring is Art at the Arb on April 9 and 10, but Macy will open the arboretum when the 40,000 bulbs planted there start blooming.

The only thing that might need fertilizing now is bulb foliage as it emerges. Lawns shouldn’t be fertilized until May at the earliest.

Some other things that are on the checklist:

▪ As far as weeding, it’s great to get out on a nice day and pull weeds. It’s still a touch early for crabgrass preventer, but you can also spot-treat broadleaf weeds such as dandelions, henbit and chickweed, McMahon says. Use 2,4-D or combination products that contain 2,4-D, MCPP and Dicamba (Trimec, Weed-B-Gon, Weed-Out), or Weed Free Zone (or Speed Zone). Don’t use Roundup or you could kill the grass. Bermuda never has gone fully dormant, McMahon says. Be sure the temperature is 50 or above if you spray.

▪ We’re also close to the time when onion plants, cabbage plants and broccoli plants can go into the ground, McMahon says. “They’re pretty cold-tolerant.” If you buy plants at the garden center or are bringing them outside from your house, be sure they are hardened off – that they have been gradually acclimated to the outdoor temperatures – before planting, she says.

▪ Tomatoes, eggplant and peppers can be started from seed indoors now or soon, unless they grow fast in your plant set-up, McMahon says. She grows hers in a warm office with lots of light, and they grow fast, so she’s going to wait so that the plants don’t get gangly by the time she’s ready to plant them outdoors, closer to May.

▪ When asparagus starts growing, if the shoots are going to get frozen, snap them off beforehand so new shoots grow, and otherwise leave it alone, McMahon says.

▪ Leave mulch on strawberries a bit longer. If it gets too warm and you want to remove it, rake it to the side and keep it handy in case you need to re-cover the plants, she says.

▪ Kemp has cut down her ornamental grasses and liriope so the new growth can come up and form tidy plants.

▪ Visit Botanica. “There’s a lot of stuff blooming that shouldn’t be blooming,” says Pat McKernan, garden supervisor, including the Peggy Clark ornamental Japanese apricot – two to three weeks early. “Enjoy it while it’s blooming, I guess.”

Annie Calovich: 316-268-6596, @anniecalovich