As cold weather arrives in North County, the ground begins to freeze, a seasonal turn that can cause damage to plants. Gardeners can take many steps to preserve their rose bushes and other perennials while preparing vegetable gardens for the spring.
“I treat annuals the same as vegetables,” Master Gardener Joan Veach said.
She explained that vegetables and annuals need to be planted each year while perennials grow back.
The WSU Extension Master Gardener program trains volunteers to be effective community educators in gardening and environmental stewardship. Master Gardeners provide information generated from research at Washington State University and other higher education systems. The program hosts classes and workshops around the county each year while also participating in community outreach.
Veach, a Master Gardener for more than 10 years, said the most effective way to prepare a garden for winter is mulching dead plants and leaves to put in the soil.
“Take a look at your garden and cut back dead and dying vegetation,” she said. “I tend to mow over it and create mulch.”
Veach said mulch protects the roots from the cold before breaking down in the soil and filling it full of nutrients for spring. She said she covers the top layer of her garden with mulch to protect and feed it.
“You can also compost the leaves if you have the ability to do that,” she said. “Anything to keep the (leaves and plants) out of the landfill.”
Veach said shredded leaves make great mulch. She uses the material for both her annual plants and her perennials.
“Right now, you can still dig up your perennials and divide them,” she said, adding that heartier perennials such as chrysanthemums can still flower this time of year.
Veach said the mulch will protect perennials’ roots throughout the winter and provide nutrients for spring, much like it does for annuals.
Veach said the same process goes for rose bushes with a few other steps involved such as cutting down the canes (the branches that bear leaves and thorns of a rose bush) down to about 3 feet in height.
“Cutting them down prevents wind damage,” Veach said. “But you don’t want to cut them super short because they may freeze and you want to protect part of the cane.”
According to Veach, the mulch should be placed 6 to 12 inches deep in the soil for the best outcome. Veach later explained that mulch is good for rose bushes but not so much for bigger bushes such as rhododendrons and trees.
“As for shrubs and bushes, bark makes a good mulch because it breaks down slowly,” Veach said.
She warns gardeners not to pile up mulch near trees and shrubs because it can cause damage.
Aside from mulch, Veach spoke about weeds in the garden and preventing their return in the spring. She broke weeds into three categories — “baby” weeds, perennial weeds and invasive weeds.
“If you have baby weeds, put down a layer of cardboard and put the mulch on top,” Veach said. “This will control the weeds without herbicides.”
She said the cardboard breaks down in the soil, leaving nutrients for spring flowers.
Veach said cardboard is great for “baby” weeds, but when it comes to perennial weeds such as dandelions, the best way to get rid of them is digging them up.
“The grounds is still soft enough right now to dig up these weeds,” she said. “If you wanted to use cardboard on these (perennial) weeds, you would need three to four layers of cardboard.”
As for invasive weeds, Veach said herbicides might be the only option as these weeds can overtake the garden and eat up all the nutrients. Despite digging them up, invasive weeds come back.
“Make sure you follow the directions on the spray you are using and cover up all the plants you want to save with cardboard,” Veach concluded.