Cold weather doesn’t have to impede outdoor planting.

For us northern gardeners, outdoor planting isn’t in full force until May – meaning several months of progress can be thwarted by the looming threat of frost.

Unfortunately, we can’t change the weather. But, we can use a cold frame.

What is a cold frame?

Essentially, a cold frame is an unheated greenhouse.

It’s a transparent, bottomless enclosure that sits low to the ground, protecting plants and seedlings from harsh weather conditions. The structure creates an insulated microclimate allowing soil and air inside to stay several degrees warmer than outside temperatures.

A cold frame refers to a general structure—the size and materiality of cold frames can vary widely.

How it’s used

Put simply, a cold frame is used to extend your growing season.

More specifically, there are three primary uses:

• Getting a head start on sowing seeds or young plants in the spring

• Keeping plants or crops growing past the first frost in the autumn

• Overwintering plants that are usually annuals in your area

To start, place your cold frame outdoors—either directly over soil (if protecting plants in the ground), or on a porch or patio (if protecting seedlings or pots).

The top of the cold frame can be opened or removed when the temperatures are warm, to encourage ventilation, and closed overnight or on cool days.

Here are a few practical examples of what you can do with a cold frame:

• Hardy annual seeds like sweet peas and pansies can be started indoors, and moved into a cold frame once they germinate. This allows them to acclimate to colder temperatures before being planted in the garden in March or April.

• Tender annuals like zinnias or tomatoes can be sown a month before the last frost under a cold frame, then moved outside of the cold frame after the threat of frost has passed. This will result in earlier blooming and fruiting.

• Cold-loving salad greens like winter lettuce, spinach or kale can be grown and harvested throughout the whole winter season if planted in late summer/early fall and grown under a cold frame.

• You can overwinter plants in containers that are usually annuals by placing the container in the cold frame. In my zone 6 climate, geraniums (pelargoniums), annual salvia and dusty miller can be successfully overwintered using a cold frame.

Make your own cold frame

A number of great cold frames are available for purchase—from local nurseries or sites like Gardener’s Supply, Amazon, even Pottery Barn. Most of these are portable options, meaning you can remove and store them over the summer when they’re not in use.

If you’d rather not spend the money, making your own cold frame is super simple.

There are a few options for DIY cold frames:

• If you’re comfortable with a bit of light building, a simple box can be made of 2x4s and a clear cover (an old window or a sheet of plexiglass, for example). GrowVeg has a useful step-by-step video if you’re interested in this method.

• If you have a raised bed in your garden, cover it with plastic (like plexiglass), weighed down on the corners with bricks, and you have yourself a cold frame.

• Easiest of all, just grab a clear storage bin (the kind you pick up at Target or Home Depot) and turn it upside down. Voila, a cold frame! This is an excellent choice for patio gardeners. I personally used this method for hardening off all my seedlings before I purchased a cold frame.

Depending on your use and budget, a cold frame can be at your fingertips in no time—and with it, an extended growing season.

🌳 Garden I’m admiring

The Sissinghurst Castle Garden in Kent. It’s one of the most popular of the UK’s plentiful public gardens. Established by Harold Nicolson and his wife Vita Sackville-West (who, fun fact, was also the lover of Virginia Woolf) in the 1930s, the couple transformed the former pig farm and POW camp into a lush, romantic landscape.

Today, the garden is run by the UK’s National Trust and is open to the public. It is known for its beauty, history and design, with the White Garden and rose collection drawing particular attention (writer Anne Scott-James considered the roses at Sissinghurst to be "one of the finest collections in the world”).

The National Trust continues to research the original designs and plants of the garden Sissinghurst and restore Harold and Vita’s original vision.

👩🏻‍🌾 Seeds I’m sowing

One of my very favorites, foxgloves. The tall, towering spires. The cheerful bell-shaped blooms. The exquisite, intricate patterns hidden inside each floret. I can’t get enough!

Growing these biennials from seed requires a bit of patience, however. Most varieties have a two year lifecycle, meaning they will sprout foliage in the first year, but will not flower until the second year.

They are entirely worth the wait, and once established will self-seed freely—ideal for a cottage garden feel.

📺 Series I’m watching

Shrinking on Apple TV+, as indulgent and feel-good as pizza on a Friday night. And Jason Segel is as Jason Segel-y as ever, which is always a win.

Okay, how are we feeling about cold frames? Thinking of giving it a go? Would love to hear what you’re growing—and feel free to reply to this email with any lingering questions.

xx

Courtney