Growing bromeliads, orchids, and other tropical plants in north Florida is easy during the warmer months. In fact, most tropical plants do well right into fall.
Many gardeners think about building a greenhouse to protect their precious tropical plants, but often put it off. Now, it is nearly December and the chance of a hard freeze in the weather forecast is increasing.
A sense of dread falls over us as we start to haul our tender plants into the garage and then back out once it warms up, only to repeat this process for every freeze through-out the winter. We have all been there. Here are a few suggestions for a quick, last-minute makeshift greenhouse.
Look for any structure that you can throw a piece of plastic over. Some structures that may work are an old swing set, a potting bench, a group of outdoor chairs, a few tomato cages – most anything will do. You can also lean two wooden pallets together and create a little pup-tent. This may not be attractive, but it is quick and easy way to get through the winter. Just promise your spouse that, ‘next year’ you will build that greenhouse. I was able to use this excuse for at least three years.
A key point to remember is that the plastic needs to completely cover the structure and make contact with the ground on all sides. Use bricks or other heavy objects to keep the plastic from blowing around. A greenhouse works by trapping the heat from the ground, so any openings or gaps will reduce the effectiveness.
Hardware stores have a ready supply of plastic sheeting. The higher the mil rating (four or above is good), the longer the plastic will last. If you are trying to cover a large structure such as a swing set, you may not find one piece of plastic sheeting that will completely cover the structure. You can try to duct tape two pieces together, but this tends not to hold up very well. If you go online to a garden supply store, you can buy plastic sheeting in any length and width you want. When in doubt, go with a larger size.
You will need to monitor the greenhouse after the freeze to make sure your plants are not overheating during the day. A tightly closed greenhouse, especially in full sun, can get quite warm. Just pull some of the plastic back to allow for some air circulation. If it is located in a shaded area, this may not be a problem. In fact, placing the greenhouse under a large tree or near the house will add winter protection.
Here is a suggestion for those of us who wait till the day of the freeze. Go to the big box store and buy a plastic shelving unit that is commonly used for garage storage. They come with four or five shelves. Also, buy plastic sheeting to fully cover the shelving unit, with extra length to lie on the ground. Buy some plastic spring clamps to hold any loose ends of plastic together. It is kind of like wrapping a large Christmas present. So, for about $50 bucks you have a mini greenhouse. So easy.
Another solution is to use a utility trailer. I have friends with a large bromeliad collection. In late fall they collect all of their potted bromeliads and place them on the utility trailer. On cold nights the trailer gets rolled into the garage. Once it warms up, the trailer is rolled back out. Do not leave them in a dark garage too long, as this will harm the bromeliads and other tropical plants.
Windows in your garage door helps with the light. If you do not have a utility trailer, perhaps you can make a smaller version. Buy two flat moving dollies and nail some boards on to the dollies to create a level platform. Now you can roll your plants in and out. This saves having to move each individual potted plant.