Cold Frame Gardening

Asked February 16, 2019, 5:04 AM EST

I recently built two cold frames to try and get a jump start on my garden. I made a mix of coco coir, home made compost, bonemeal, calcium, Epsom salt and a 4-4-4 organic fertilizer for my soil. It is mostly just coco coir and compost though. I planted carrots, radishes, spinach and lettuce on Feb 14th. While it has mostly been around 40-45 degrees during the day and around 30 at night the cold frame seems to maintain a temperature around 10-15 degrees warmer. My question is, with the temperature fluctuations like they are, would I expect to be successful in the germination of the mentioned veggies? I have an automatic lid lifter for the cold frames that open the lids when the inside temperature reaches around 75-80 degrees. And once they germinate and get around an inch or so, would I need to be concerned about damaging them due to the colder weather? Thank you.

Lane County Oregon fruits and vegetables season extension cold frame

7 Responses

Are you planning on growing them in the cold frame until harvest? If so, be sure to thin adequately. All but the carrots should do well. Carrots are very slow to germinate and in cool soil may take a month or not germinate at all. Have you taken the soil temperature about 9 am? If the soil is under 50, all germination will be pretty slow. Once germinated all these crops are quite happy even when cold. The lid lifter is a crop saver for sure.

Good luck

Thank you for your help. Yes, I plan to keep them there until harvest but am going to plant broccoli, kohlrabi and cauliflower to plant out later. Regarding the carrot seeds not germinating, I placed them in a pint jar with water and left them close to our woodstove. It took 5 days for them to germinate and I plan on putting them in soil in the cold frame today. I don't know if it will work because the germinated seeds might get too cold, I don't know, it's just an experiment. Thanks again for your help.

I would love the result of pre-spouting the carrots. I know of no one who has done this and you may be onto something. You are really on top of the timing, congratulations.

The little sprout coming out of the carrot seeds are about 1/4 inch long. About 70% of them have germinated so I think I'll wait another day or two and then plant them out. I was thinking it would be pretty tedious and hard to plant the germinated seeds in soil so I am going to mix cornstarch and water together and boil it until it gets a gravy like consistency. Then I am going to cool the mixture and very carefully fold the seeds in the mixture. Then I am going to pour the mixture with the seeds in a zip lock bag and cut a little of the corner off. Then make my furrows and squeeze the mixture with the seeds into the furrow. Cover lightly with vermiculite and keep moist. I have no idea if this will work. If the seeds can take the cooler weather after they have geminated, I think they will be fine. Time will tell and I will let you know. The temp in my cold frame today was 80 degrees and the outside temp was around 40. I am amazed at the cold frames. I wish I had used them more in the last 50 years. Us old folks don't like change much haha.

Great idea. I am excited about your experiment. Trying to just plant the tiny germinated seeds would be indeed difficult. I have used a Knox gelatin mix for sowing little seeds in the past, but they had not yet germinated.

So....I squeezed the germinated carrots in the cornstarch mixture into potting mix and covered with vermiculite. It was pretty cold outside but warming up to around 60-70 inside cold frame. As of 03-10-19, I would say about 70 percent of them have emerge from the mix and are about 1-2 inches tall. So I experimented again. Placed a bunch of carrot seeds on wet paper towels and put into a zip lock bag. All germinated in about 5-7 days. I then picked each one up and placed them on top of potting mix and covered with vermiculite (inside of house). As of today (03-10) they are doing great and are about 2 inches tall. I placed them outside in the cold frame today so we'll see how they do. Also, my spinach, lettuce and radishes are going gangbusters outside in the cold frame.

I am excited about your technique with the carrots as they always cause me problems of germination and growth! You are an extraordinary grower. How exciting.
Thanks for the follow up.