In my first book, The Year Round Vegetable Gardener, I detailed the many ways I use cold frames to extend my homegrown harvest into winter. However, a cold frame is also an easy way to get a jump start on spring, planting weeks – even months – earlier than in traditional vegetable gardens.
Spring cold frame tips:
- Clean! On a mild day, spring clean your cold frame tops! Whether glass or plastic, the sashes can eventually get grimy and giving them a quick wipe down will allow more light to reach your plants. More light = healthier plants and faster growth.
- Vent! Whenever the temperature climbs above 4 C (40 F), I crack open my cold frames to prevent heat build-up. Crops that are grown too warm will have soft foliage and be prone to damage if the mercury suddenly drops. I keep it simple and use a piece of scrap wood to prop open the tops. On mild rainy spring days, let Mother Nature water your crops by opening the cold frame completely.
- Sow! It’s best to direct seed veggies into your cold frames. Transplanting seedlings that were started indoors usually results in disappointment as those tender plants aren’t tough enough for the temperature fluctuations found in a spring cold frame. However, you can use your frames as a seeding bed to start crops like broccoli, kale, and cabbage, eventually moving them to the open garden when the spring weather is more settled.
- Feed! Once your early cold frame crops are done, pull up any debris and amend the soil with compost or aged manure. I often give the soil a boost by growing green manure crops in my frames – an easy – and cheap – way to improve the soil.
Spring cold frame crops:
- Greens! All of the cool and cold season salad greens can be planted in an early spring cold frame. Common crops like lettuce, spinach, and arugula, as well as lesser known ones like mizuna, mibuna, and broccoli raab.
- Roots! My favourite roots for cold frames include baby beets, Japanese turnips, radishes, and carrots.
- Onions! Scallions are one of the easiest crops to grow in a cold frame. My go-to scallion is Evergreen Hardy White, which is reliable and very cold tolerant. Or, try baby onions like Purplette! Ready just 2 months from seeding.
What do you have growing in your spring cold frames?