Getting through a cold night

We had an unexpected cold snap just last week. We were going along fine. It was an overly warm spring with temps in the 90s when they should have been in the upper 60s. I decided to play it safe because it was my first gardening season in about 6 years so I timed everything to be in on or around the last frost date. I took an extra long time preparing the planting beds and even more time with the planting holes. In the end I would say I was right on track for our Northern Prairie climate, getting tomatoes in on May 24th and peppers in between June 1 and 6. Then everything went wrong.

Somewhere around June 8th it got cold and wet. That was fine for most of the garden, but I was concerned about the peppers. For most of the peppers I picked off the flower buds as I planted so I would get extra strong plants but for a few I left them on so I could compare the difference and hopefully get some nice early peppers. The day and night temperatures weren’t too far apart at about 50F. Then on the 11th and 12th the low was between 4 and 6 C (40 F). This wouldn’t do. I was worried the buds would drop and the plants would get stunted.

A nice thing happened on the afternoon of the 11th - the sun came out. Not a lot but enough to warm that black solar IRT plastic mulch I was using which in turn helped warm the soil just a bit. I had some cozy coat season extenders on my tomatoes which were at the end of their season so I moved them over to the peppers. I didn’t have enough to do all my peppers but I stretched them out at the base making the as wide as I could at the bottom. I had some milk jugs out in the garden filled with water in case of an emergency frost and so I made sure they were in the sun to warm up. Once the evening came I moved the milk jugs onto the black plastic in between the plants where there was a gap from the lack of cozy coats.

Things were working out pretty well for one reason only - no wind. Had there been a wind the warmth given off by the season extenders and milk jugs would have been carried away. On a calm night though that warmth will help displace the cold air and keep it just a couple degrees warmer, which may be enough to help your plants.

If you are faced with a cold forecast early in the season for your peppers or melons and you don’t have the option for a fancy row tunnel, here’s some options:

• Season Extenders - these are cylindrical shaped plastic that you form into a cone and put over your plants. They have several small tubes that you fill with water. They water stores heat in the day and releases it at night. These don’t help the much in the event of frost because the water probably won’t store enough heat to make it through until dawn when needed most. Where they do come in handy is pure shelter. They keep the wind off the plants and will retain some heat for a period. Even better, by sheltering your plants from the wind, the heat already stored in the soil radiates upward toward the top of the cone where it gets trapped. It works better yet if you planted on black plastic mulch because that soil will be even warmer. This is perfect for a cold night. Remember to close the top of the tube at night.
• Milk Jugs - like the season extender above the milk jug will hold some water to give of heat later. I always keep these around in the garden until the weather is predictably warm. The problem is that a one gallon milk jug only holds one gallon. A season extender like mentioned above holds 3 gallons. This isn’t bad, but it is limited heat. Again, this works best on calm nights when the heat stays near the plants. If you have a bad forecast that calls for wind, you can still use a milk jug full of warm water to provide shelter from the wind for young transplants or smaller plants like peppers. One thing I like about milk jugs is that you can fill a couple with hot tap water and put them out later in the evening or right before dawn if necessary.
• Floating Row Covers - also known as frost blankets. This is a simple woven fabric blanket that you throw over the row. These will protect against a frost by about 2 degrees. They are good for cool nights and in my opinion would work best with black plastic because they would help trap in some of the heat radiated from the ground. The problem with peppers is they have pointy growing tips which could rub against the fabric and require protection from breaking. Again, floating row covers would be best used on a calm night as any movement could damage the plants. They would be more appropriate on melons or cucumbers on a windy night as they could be anchored without damaging the plant. Suppliers like Johnny’s Selected Seeds carry quality row covers for the home or commercial gardener. I recently bought a frost blanket locally and found that it was too expensive, and not nearly wide enough to fit over top of a simpy row of peppers that are 18” apart and have bamboo sticks for support. Buy a quality blanket that is wide, long and strong enough for your needs. Then buy a few more to keep around for late summer frosts.

There you go. Some ideas for getting through a cold night. There are countless others but I haven’t personally tried them. Many, such as hot caps, only work with small transplants and wouldn’t have been a good fit for pepper plants which have been well started indoors and nearing their maximum size. Hot caps and cloches would be a good fit for melons and peppers while they are still small. However, if you are resorting to these techniques when planting early in the season then the plants will soon outgrow the hot cap and your weather may not have warmed up. In this case you are better with something like season extenders for peppers or row covers and poly tunnels for peppers and other crops like melons which will give you consistently warm day temperatures and plenty of warmth at night. This way you can ensure nothing will keep you from harvesting your early garden plenty early.