Pritha Golden Steele
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December 7, 2023

Using Row Cover And Mulch To Get More Out Of Your Winter Garden

Have you ever planted fall or winter veggies only to grow small plants that never reach maturity? Or have you lost your plants to frost before you even get to harvest them? By no fault of their own, many people plant vegetable starts from the nursery without knowing that the plant is being sold during a time of year when it will never become fully mature before cool temperatures slow the plant’s growth to a sloth-like pace.

First and foremost, knowing what to plant when is the foundation for success in a winter garden. Read our blog post Top Ten Winter Vegetables For Your Home Garden to learn more about when to plant some of the most popular winter veggies. Once you have established your fall and winter garden, you can use season extension techniques like row cover and mulch to enhance your harvest.

What is row cover ?

Row cover is an agricultural fabric designed to cover your crop. Some covers are primarily used to keep insects from your plants, while others are used to trap heat or for both. During the coldest months, we like to use a thicker row cover (also called frost blanket) which allows sunlight and rain in, is breathable, and acts as a miniature greenhouse by trapping heat from the sun during the day and slowing the release of heat at night.

When using a frost blanket in your fall and winter garden it has two primary functions. First, the constant increased ambient temperature causes more rapid plant growth. Second, it protects plants from frost damage.

When should I use row cover?

Below are some basic guidelines for when to use frost blanket in the fall and winter months in Portland, but keep in mind that these are generalized. Variety and maturity of the plant, your specific microclimate and winter conditions are all important factors affecting plant hardiness.

If you have fall or winter crops that are smaller than is ideal, you can speed up their growth by covering them with row cover once daily highs are below 65 degrees. To use row cover for frost protection, start tracking the night time lows in the second half of October. When you see night time lows below freezing it is time to cover select plants in your winter garden.

Lettuce, cilantro, bok choi, and celery will tolerate some light frost but repeated frosts or harder frost will damage and eventually kill the plant. Cover these plants with a frost blanket, and you will be amazed by how long you can extend their harvest into the winter.

Spinach, escarole, and scallions are quite frost tolerant in terms of survival, but cold and wind can damage their leaves and reduce the harvest. Use of a frost blanket will enhance both leaf growth and quality, notably increasing your harvest.

Collard greens, kale, chard, broccoli, cabbage, cauliflower, Brussels sprouts, parsley, arugula, leeks and many mustard greens are extremely frost tolerant and will produce high quality crops without any need for cover.

Mulch for season extension?

Typically our winters are mild enough that the soil protects root crops such as carrots, parsnips, beets, turnips, rutabagas and cold hardy radishes sufficiently from damage. To give your roots (especially radish) extra protection from our coldest temps, you can insulate them with 6” of dried leaves or straw in the fall. Keep in mind that while the leaves of some roots (like carrots) may die off during the winter, that does not mean the root is dead. In many cases the roots are even sweeter after a frost! So don’t forget to harvest your roots even after the leaves are gone.

How do I use row cover?

We like to make small “hoop houses” over our plants by simply pushing heavy gauge metal wires into the soil and then securing the row cover in the ground with metal staples. This keeps the cover off of the plant and often results in a higher quality harvest. This being said, frost blankets are designed to be able to sit directly on the plant without hoops as long as you leave some breathing room and fabric isn’t pulled tight against the plants.

Eat abundantly year round!

One great thing about growing veggies in Portland is that our location west of the Cascade Mountains has a relatively mild winter compared to many eastern counterparts at the same latitude. To the surprise of many, we really can eat a nice diversity of food from our gardens year-round here. If you are someone who wants to eat from your garden all year but has had mixed results, knowing these season extension tips will prove to be a great tool to have in your tool belt.

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