April Fool’s Day is past and I hope no one was fooled into planting their tomatoes outside yet! However, I’m sure some avid gardeners have planted their “very hardy” vegetables: asparagus crowns, broccoli, Brussels sprouts, cabbage, kale, lettuce, onions, parsley, peas, spinach and turnips. “Semi-hardy” vegetables such as beets, carrots, cauliflower, parsnips, radishes, Swiss chard and potatoes are planted from April 1 to May 1. “Frost-tender” veggies, including celery plants, green beans and sweet corn, go in the ground after May 15. The common favorites: cucumbers, eggplants, peppers, squash and tomatoes are all “cold-sensitive vegetables” and are best planted one to two weeks after May 15 to June 15.
Be aware that these dates are guidelines. Each area has its own microclimate and you need to know whether your last frost day averages May 15 or later. As I have mentioned in previous articles, I don’t usually plant cold-sensitive veggies until after June 1 in my part of Washoe Valley, unless I use season extenders.
A traditional season extender is the hot cap, used over individual plants.
“A hot cap is anything that covers a plant to retain the heat around it. Historically, large jars with the bottoms cut out were used for this purpose,” (Gatzke, University of Nevada Cooperative Extension).
Walls of water are commonly used, readily available, season extenders. They are plastic sleeves that go over plants. They are made up of about 16 cylinders that you fill with water to absorb heat during the day and keep plants warm at night. Supposedly, when you use them you can plant cold-sensitive veggies six to eight weeks prior to the last frost and they will be protected down to 16 degrees.
Some season extenders can be made from materials on hand. Put a clear glass or plastic panel in the top of a box to create a “hot box.” Place trash cans or upside-down five-gallon buckets over plants at night and remove them during the day. Or place a paper shopping bag over your plants at night. Weight the handles down so the bag stays in place. Blankets laid over arched frameworks will protect plants without weighing down tender seedlings. Or you can buy commercial “frost blankets” or “floating row covers.” Floating row covers don’t need a structure to support them because they are lightweight. They can provide an additional seven to 24 degrees of protection while still letting light through.
For more information, go to www.unce.unr.edu, and search for “Plant Season Extension in the Desert” under Publications.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at skellyj@unce.unr.edu.