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Cold Frame Salad Gardening

Cold frames are like outdoor mini glasshouses for winter vegetable and herb growing.

Garden-fresh eating does not have to end in the fall. The onset of chilly weather means it’s time to enjoy cold-frame salad gardens filled with easy, cool-season greens, root vegetables, and annual herbs. These crops are fast to germinate and grow, and they will tolerate serious cold weather if your frame garden is properly placed, prepared, and maintained.

What is a Cold Frame?

In 2012 I co-wrote an article with John Everard about how to build your own cold frame. This is the cold frame that he designed! (See building details in the linked article below.) (Image by Jessie Keith)

A cold frame is a cross between a raised bed and a small, sunken, covered greenhouse. It is lowered into the ground to reduce winter freezing of cold-tolerant greens, herbs, and root vegetables. Most cold frames are designed with sturdy sides of either wood, stone, or brick, and they are topped with framed glass or plexiglass lids that can be lifted on unseasonably warm fall and winter days.

Cold frames were first popularized in Europe, where winter growing conditions are generally mild, but they are also useful for American gardeners. You can build your own cold frame or purchase a premade one. Building your own has its advantages because you can create something more for less, if you know what you are doing. For a great step-by-step building guide, please click here to read this article that I co-wrote with biologist and builder John Everard for Wilder Quarterly in 2012. John created a very useful design that can be sunk into the ground in our USDA Hardiness Zone 7 area.

Cold Frame Siting

Cold frames further south can be shallower because it’s warmer.

All cold frames should be placed in a somewhat elevated location with full sun and soil that drains well–standing water and vegetable cultivation do not go hand in hand. Some steps regarding cold-frame gardening depend on one’s location and climate. In the north, a cold frame should be placed in a sunny, south-facing spot close to the home. If you can, sink the frame a few inches below the soil level. The reflective heat from the home will provide a little extra winter protection, the south-facing sun will help heat the cold frame all winter long, and the added depth will reduce the chances of freezing on cold nights. Further south, you can choose a spot away from the home, and sinking the frame is not necessary. No matter where you live, be sure to be watchful of your cold frame on uncommonly warm winter days. Prop the tops open during the day to keep the internal temperature from getting too hot and stressing your greens.

Cold Frame Soil

Rich, dark soil is best for cold frame gardens.

Dark, lofty, highly amended soil that holds water well will yield the best vegetables. Start by amending the ground soil in the frame with good compost, like Black Gold Natural & Organic Garden Compost Blend. A 1:2 ratio of soil to compost is recommended, especially if the soil is high in clay or sand. Another option is to fill the bed with Black Gold Natural & Organic Raised Bed and Planting Mix. Adding a layer of compost as a protective mulch is also important and can serve as further insulation. (Click here to learn more about creating the best soil for raised beds.)

Cold Frame Salad Crops

Rather than harvesting whole lettuce heads, I recommend snipping away leaves for cut-and-come-again salads.

It is essential to grow cool-season, frost-resistant crops. These are largely cool-season greens, herbs, and root crops. There are lots of greens for the job such as mâche, kale, lettuce, mizuna, spinach, and Swiss chard. Any lettuce will do, but small, fast varieties are most favorable. Salanova baby lettuces (55 days from seed) produce sweet and crunchy heads of green and purple very quickly, and the looseleaf lettuce Baby Leaf Mix is a reliable cut-and-come-again mix. Spinach thrives in cool weather and may have smooth or savoyed (puckered) leaves. I recommend both the 1925 heirloom ‘Bloomsdale’, which has large, savoyed leaves and is slower to bolt than most, and the smooth-leaved ‘Corvair’, which is resistant to the fungal disease, downy mildew. Arugula cultivars vary in leaf shape, color and heat. The popular ‘Wasabi’ is an easy-to-grow selection with leaves that truly taste like hot wasabi, and the newer ‘Dragon’s Tongue’ is a visually pretty, finely cut variant with purple-red venation.

In the deep winter, cool-season root vegetables bulb up more slowly.

The best root crops include winter carrots and radishes. Radishes are by far the fastest, and my favorite variety for crisp, sweet flavor is the French breakfast radish D’Avignon. Click the following link to learn more about growing winter root crops and click this link to learn more about growing cool-season greens.

For delicate cool-season herbs, try cilantro, dill, and parsley. Cilantro likes it cool and may produce leaves throughout winter. When the weather heats up, it will produce starts stems of white flowers and bulbous seed heads that can be dried and crushed to make the spice coriander. Dill will bear ferny leaves that taste great in salads, spreads, and fish dishes. Lush clumps of curly or flatleaf parsley will also flourish in cold frames all winter long.

All of these plants can be directly sown into the frame from seed. They sprout fastest in the fall when germination temperatures are more moderate–between 70 and 40 degrees F. Some need to be sown on the soil surface, particularly the small seeds of lettuce, which need light to germinate. At sowing time, start by wetting the soil, and then gently sow and pat the seeds down. Follow up with a little more water to wet the seeds. Be sure to label all seed rows with labels showing the plant names and sowing dates.

Harvest salad leaves, herbs, and roots as needed through winter–I tend to use shears to trim off what I need on a given day. By early spring, the cold frame garden will begin to look tired. Feel free to clean it out and begin planting new vegetables for spring.

How Do You Safely Overwinter Rose Containers?

How Do You Safely Overwinter Rose Containers?

“I have roses in containers. What is the best way to overwinter them in zone 6b? I have a Winchester Cathedral, a Young Lycidas, and a Jubilee Celebration. There is another one that looks similar to the Young Lycidas, but the flowers and scent are a bit different. It is also a David Austin rose, but it was unmarked when I got it from a nursery a couple of years ago.” – Question from Kristen of Stephens City, Virginia

Answer: Start by identifying the hardiness zones for each rose, if you can. In this instance, Winchester Cathedral, Young Lycidas, and Jubilee Celebration are all hardy to USDA Hardiness Zones 5-11. The rule of thumb is that potted shrubs must be at least two hardiness zones hardier than yours to reliably survive winter in an exposed container. Because you live in a Zone 6 area, and your roses are not hardy to Zone 4, you will need to protect your potted roses from hard freezes.

How to Protect Potted Roses from Hard Freezes

There are several methods. Just remember, that regardless of where you place your rose, the pot cannot become completely dry. If placed in a garage or under a patio or eave, supplemental water will be needed to keep the plants alive. Too much moisture can also be detrimental, so I recommend twice-monthly watering through winter, to be safe. Here are four reliable methods of protection.

  1. Protect the pots and roses where they stand. Mound Black Gold Garden Compost Blend around the base of the rose, wrap the top in burlap (tops can be tied or lightly pruned to make this process easier). Mound mulch or moistened chopped leaves along the base of the pot as insulation.
  2. Move the pots of a protected area against the side of the house away from wind. If you live in a very windy area, use this outdoor method. Mound compost around the base of the rose, and wrap the top in burlap. Mound mulch or moistened chopped leaves along the base of the pot to act as insulation.
  3. Move the pots to a protected garage. Place your pots in a safe zone in the garage. Slightly dry roses overwinter better than overwatered ones, so maintain light watering as detailed above.
  4. Move the pots to a protected basement or root cellar that remains cold enough to keep them dormant. Freezing or near-freezing temperatures are necessary.

In the spring, remove any protective coverings and organic layers. It is especially important to move the compost away from the base of the rose and into the garden.

I hope that these tips help!

Happy gardening,

Jessie Keith

Black Gold Horticulturist

How Much Cold Can Petunias Handle?

How Much Cold Can Petunias Handle?

“What is the coldest temperature petunias can handle?” Question from Barbara of Racine, Wisconsin

Answer: Petunias are true warm-season annuals that cannot withstand really chilly temperatures without damage. Ultimately, they grow best when nighttime temperatures are between 55 and 65 F. (14-16 C.) and daytime temperatures are between 61 and 80 F. (16 to 20 C.). Many newer cultivars are able to withstand hotter temperatures, but no petunias thrive in chilly temperatures. When spring temperatures dip below 40 degrees F, either cover your outdoor petunias with frost cloth or bring them indoors. Temperatures below freezing will kill them in a jiffy.

Happy gardening,

Jessie Keith

Black Gold Horticulturist

My Spring Bulbs Seem to Be Emerging Early. Will It Hurt Them?

 

“Winter is not over, but we have had warm spells. Daffodils are already pushing up. Will another hard freeze kill them?” Question from Richard of Winston Salem, North Carolina

Answer: You need not worry. It is not uncommon to see blooming bulbs in the snow, daffodils included. That’s because most of these early bulbs are very tough and resilient to spring cold snaps. It would have to get into the teens or even single digits Fahrenheit to really do emerging spring bulbs serious damage. So, let them be and emerge in their own time. They will bloom and flower for you with no trouble.

Happy gardening,

Jessie Keith

Black Gold Horticulturist

How Much Outdoor Cold Can Ginger Plants Survive?

“What is the minimum temperature for growing ginger plants outdoors?” Question from Susan of Pembroke Pines, Florida

Answer: Culinary ginger (Zingiber officinale) is a true tropical plant that originates from Southeast Asia. It survives in USDA Hardiness Zones 9 to 12, which means that it can withstand outdoor cold reaching down to 25 to 30 degrees F, no colder. Temperatures on the coldest end will still stress plants out and cause their foliage to die back, so it’s best to keep them in a warm, humid location if the weather really takes a cold turn. But, ginger should grow really well in your zone 10 location under normal weather conditions.

To learn more about growing ginger, click here!

Happy ginger growing!

Jessie Keith

Black Gold Horticulturist