Protecting Overwintered Spinach from Frost

Finally all of the snow has melted and I am beginning to prepare my garden for spring planting. I have a few spinach plants that have made it through the winter. Last fall, I piled leaf mulch around each of the plants. Despite the frigid temperature, I have green plants in my garden. I am experimenting with methods to keep the spinach alive long enough to grow to an edible size. Do spinach plants need protection from spring frost?

My over-wintered spinach! Some new leaves are sprouting.

My goal is to create a mini-greenhouse effect which will allow warmth to build up and encourage growth. I went to my local thrift shop and bought 2 large glass bowls and 1 large plastic bowl. My husband commented that the glass may block UV rays which would inhibit growth. I am testing out both and we will see if the UV rays make a difference. I have also left one spinach plant completely uncovered. 

So far, this method shows no advantage over just leaving the spinach to fend for itself. On the upside, the covered plants are still surviving. Here are some thoughts on flaws and improvements. First, lots of condensation form on the inside of these bowls. You can see that below. In general, wet leaves are a bad thing for plants. The moisture, among other things, prevents the plant cells from breathing. I also need to add materials that have a higher heat capacity under my bowls. Having a high heat capacity means that a material can store lots of heat during the day and then release heat at night. This mitigates the temperature drop at night. Water is the best option here but rocks can work well too. The verdict?

Check out that condensation. It's not good for the plants.

Spinach plants that made it through winter probably don't need the extra layer of protection. The seeds I just put in the ground need the heat more. I may transfer the bowls over key patches of seeds. Perhaps that will heat enough during the day to stimulate germination.

The Gist:

• Using leaf mulch to protect spinach plants over the winter: Totally worth it
• Using glass bowls to protect overwintered spinach plants during spring: More problematic than not

Do you protect your overwintered vegetables in the spring? Also, I had some carrot plants that made it but they were too young by the time winter hit. Have you successfully overwintered mature carrots? What time of the year did you plant them?