Are you a dedicated vegetable gardener? If so, I know you thrive on growing plants. Do you marvel at tiny seeds sprouting and growing to vegetables? Nothing better for the soul or our stomachs!
20 years ago, I embarked on the journey of winter growing. I wanted to extend our harvest seasons and to have vegetables over the winter. I wanted to have early spring crops. I wanted—nature laughed!
So here are some tips and strategies based on what I have learned (and continue to learn) about growing in the winter months. Winter is a challenge for us here in Delaware, because our days are shorter, and the night-time temperatures are below freezing.
Look for cold-hardy varieties that can handle the level of protection that you can provide. Adjust your expectations of how quickly things will grow. Supplemental heat makes a huge difference, but you have to evaluate the cost of heating compared to what you get out of it.
Here are some strategies to start:
1. Light—as much as possible! Anything with a flower needs at least 10 hours of daylight in order to flower, pollinate, and produce. However, plants that do not flower can get by on 4-6 hours of daylight. Good thing, because the winter months are often cloudy, and the light is often diffused for much of the day.
In Delaware, where we are, we lose our 10-hour mark on November 15, and go back above 10 hours on January 26. Google knows the answer to your 10-hour marks.
So, what grows in lower light levels? Lettuce, arugula, chard, collards, kale, mustard greens, mizuna, spinach…you get the idea. The leafy greens. Plus, you can grow beets, carrots, radishes, carrots, daikon, turnips. They grow in the dark, underground, but need light to feed the top growth.
2. Wind protection—winter winds are ferocious on plants! Some sort of protection is necessary, keeping in mind that you want to let in as much light as possible. You can build a cold frame, cover with row cover, build a lean-to, use container pots in a sun room in your house, build a mini-greenhouse with glass walls and roof.
Anything with glass or greenhouse plastic will amplify any sunlight and help warm the plants up during the day. Night-time temperatures, though, can get pretty cold. Each unheated layer that you give the plants gives you about 4 degrees of protection. If it goes down to 20, you will have 24 degrees inside your area, without supplemental heat. If you add a row cover over your plants plus the outer cover, you have 8 degrees of protection.
3. Growing time without heat—this is a tough one. Basically, you need to have your plants at close to maturity before you go to fewer than 10 hours of daylight (which usually coincides with cold nights and cooler days). Your plants will sit there and not grow very much until you get above that magic 10-hour mark (which coincides with better daytime temperatures and slightly higher night time temperatures). You will be able to harvest from your plants, but they will not be growing very much to replace what has been harvested until early March.
4. Growing in a lean-to or mini greenhouse. I get it, I do. The temptation to put in lots of shelves and pack that space with seedlings and plants is overwhelming. Especially if you are putting a little heat in there to promote growth. However, plants on lower shelves get less light than those on upper shelves. Consider rotating the plants on the shelves to give them access to light. Container pots that can be staggered in their stacking are a great way to use your vertical space and still provide adequate light.
If you have a structure up against a house wall, it gets the benefit of residual heat from the house. Have the structure so that you are south facing for maximum sun exposure.
It’s hard to believe, but you also need to keep in mind venting on sunny days, as it can get too warm too quickly in a little house. You will get a build-up of condensation, which drips on the plants and can cause mold. A fan, or a way to crack a door or window, is helpful to keep the air circulating and bring some fresh air into the house.
5. Where do those aphids come from? You have seen them appear all of a sudden on house plants or in a greenhouse. They are a complete nuisance in a closed setting. Proper air circulation and venting help a lot in keeping aphids out of your plants. Inspect your leaves regularly and wash off promptly. We use a peppermint solution which helps if those pesky critters show up. We also have fans which run 24/7 in our tunnels.
This is a lot of information to take in, and there is more to come. Visit us at our farm market at 1431 Foulk Road, Wilmington, Delaware, to see what we are growing all winter.
Follow us on Facebook @highlandorchards and Instagram @highland_orchards for behind-the-scenes views of what we are doing. Feel free to email with questions or comments to [email protected].
Part II, with 5 more tips will be coming soon. Thank you for being part of the growing community!