We may be one month into spring, but May flowers may not bloom in Chicago with winter-like temperatures still in the forecast.
A chance for frost hits the Chicago area overnight Thursday and into Friday morning, which is bad news for plants and flowers. To make sure your springtime gems aren't wasted this year, follow these tips to protect them.
Plants Most Susceptible to Frost Damage
Today’s Homeowner says the plants most vulnerable to frost damage include houseplants, tropical plants, spring-blooming shrubs and trees (e.g. azalea, rhododendron and cherry), citrus trees, tender bulbs (e.g. dahlia and elephant ear), warm-season vegetables (e.g. tomato, corn and pepper) and warm-season plants (e.g. impatiens, petunia and geranium).
It's important to note that different types of plants react differently to frost. While both tropical and annual plants cannot survive freezing temperatures, short-lived annual plants at least disperse seeds as a way to restock their numbers upon warmer weather. Plants most suited to withstand or recover from freezing temperatures are root-hardy and full-hardy perennials (plants that live for more than two years).
How to Protect Plants from Frost Damage
Bring Plants Indoors
Bring frost damage-prone plants in containers indoors during cold weather. It is recommended to dig up tender bulbs and store them in a cool, dry place.
Water Plants Before Nightfall
Watering plants helps prevent further damage by releasing moisture into the air around plants, which keeps the air somewhat warmer.
Provide a Slight Breeze
The Garden Helper blog notes that even a slight breeze helps prevent cold air from settling near the ground at night. Artificial breeze via electric fan can be used to provide this slight breeze. Just make sure to protect the fan and all electrical connections from water and the elements.
Cover Tender Plants Before Dusk and Overnight
Covering plants up before nightfall allows plants to keep as much stored heat in your garden as possible. Some of the best items used to cover up plants can be found in your household: linens, cardboard boxes, plant containers and plastic row covers.
Regardless of what you use as a cover, make sure to have one that can also cover the soil on each side of the plant. Remove covers once the frost has thawed.
The Morton Arboretum recommends adequate mulch to help moderate soil temperatures and protect roots. A depth of 3 to 4 inches is sufficient for trees and shrubs. A 1 to 2 inch depth is good for perennials.
Purchase cold frames to go over tender plants, such as vegetables.
Plant a Frost-Resistant Garden
Growing a garden geared towards surviving frost and freezing conditions is the best preventive measure.
In addition to choosing plants built to withstand frost and freezing temps, The Garden Helper recommends planting tender plant species on higher ground or slopes where the cold air will flow past the plants as it moves to the low point. In other words, “any sloping area is far less prone to frost because the cold air can’t settle there as easily.”
As far as fertilizers go, discontinue fertilizing plants in early September so that no new foliage is on the plant once cold weather hits. Older leaves are tougher and less prone to frost damage.
The Morton Arboretum recommends planting plants from warmer climates or plants that have been grown in greenhouses after May 15, the last frost day in northern Illinois.