Plant Protection from Frost - Florida DIY Greenhouse & More Frost Protection Tips

Plant protection from frost

So, it is forecasted to be a little chilly for Christmas here in Florida, which means that plant protection from frost is on all gardeners' minds, especially those of us who grow our own food. 

frost in St. Augustine Florida

From 60 degrees to 25 degrees Fahrenheit at night here in St. Augustine, the local gardeners are in prep mode, all while the kids are hoping for a white Christmas. 

This fall we built our own greenhouse, a temporary Florida greenhouse for plant frost protection, but we weren't planning on using it until January or February. Thankfully it is already set up and ready to go, and all we need to do is move plants around and tighten it up. 

How to build your own greenhouse

When you live in zone 9a/9b, it is tempting to push the growing zones as we have very few nights with a chance of frost, and many tropical fruit trees will do fine down to 28 degrees, if they are mature and the trunk size are of a certain size. However, as a frugal gardener we start fruit trees from seeds, cuttings and buy them small, which is the reason why we expanded our temporary greenhouse this year to one with a DIY greenhouse with a more permanent skeleton.

Plant Protection from Frost: 

Plant protection from frost in Florida does not mean that you need to go out and build a fancy greenhouse. As we explained in our build a cheap greenhouse post, it can be done on a budget as low as $12 - $20, and this simple set up is what we have been using for years in addition to the occasional cover with sheets.

  • Consider how temporary you want your greenhouse
  • How many plants do you have to protect?
  • How big are the plants you want to protect from frost?
  • How cold hardy are the plants and tees you're trying to protect?
  • Do you have other protections against cold?
  • Grow your plants close to your house for frost protection
  • Create a microclimate by planting in between two homes, near structures, concrete walls and fences.
  • Do you want to be able to stand and move around inside of your temporary frost protection?
  • Easy access
  • Access to a water source
  • How can you source affordable materials?
  • How will you attach your materials?
  • Make sure you have something to keep the frost protection tied down in case of winds. We like to use bricks and heavy pots for this purpose. 
  • Make sure that the diy greenhouse is taller than your plants, so plants won't get burned during the daytime.

We've been collecting free wood from the side of the road and through Craigslist for a few months, and it is amazing what you can gather for free, if you just keep your eyes open, or you can join your local Buy Nothing Group as well.

Where to find free wood
Free wood

Hubby's summer boss gifted a big clear tarp used for roofing for our project, but you can find it cheap at Lowe's, Amazon or Home Depot etc., or see the links below for other options. We got the 6 mil plastic, which should hold up for a while. If using plastic, only use it for one year or it will start disintegrating.

As with most building projects at our house, it is a shared project with vision, sketches and practicality in mind, and these husband-and-wife projects always test our communication skills, but in the end two heads are better than one, and sometimes the kids help out too.

Build Your Own Greenhouse Cheap:

  • Get free materials or use secondhand materials
  • Source materials on the side of the road, from friends and family, through Craigslist, Facebook marketplace and your local Buy Nothing group.
  • Use plastic materials such as high density drop cloths, or for better quality use something like this 6 mil greenhouse plastic or this clear tarp with grommets. Plastic should only be used for a year, or it will start deteriorating.
  • The best solution is if you can source plastic roofing panels for free, or want to invest into a more permanent soulution, these work well too. 
  • Measure, and double measure
  • Sketch out your project.
  • Lay out your materials before you start cutting.

How to protect plants from frost

The vision was a semi-permanent structure that will last a few years, where it is possible to cover up a large area in very little time for cold nights...and arctic fronts, while it should be easy to pull back and open up on sunny and rainy days.

How to protect plants from freeze

For the past year or so, our old tomato garden at the side of the house has been replaced with a nursery for young tropical or semi-tropical trees and plants such as mango trees, Jamaican strawberry, cherry of the Rio Grande, jaboticaba, black sapote, white sapote, blackberry jam tree, a dragon fruit area with five different types, chaya, pigeon peas, salad trees and more.

The entire area is surrounded by passionfruit vines currently with fruit, and on the outside we've got peppers, tomatoes, papaya, herbs, moringa and Mexican sunflowers growing tall.

Florida DIY Greenhouse for plant frost protection

We had relocated any plants and trees that needed protection at around feezing, but with temperatures forecasted to reach as low as 25 degrees, we will pack the area even closer and add as many potted plants as possible including some of our tropical spinaches.

We're counting on the heat from the house to help aid in keeping the temperatures above freezing, the fence on the side to keep cold winds out, and gallon jugs filled 2/3 of the way with water placed inside the greenhouse and the closeness of the plants will also help keep them safe.

Covering plants for frost protection 90 competition

Now, we have lots of bananas that we are worried about, including our current double-blooming Dwarf Musa Cavendish and lots of papaya, but they will ultimately have to fend for themselves as they have done so many times before albeit never below 29 degrees. 

frost protection Cranberry Hibiscus

We also have volunteer tomato plants and cranberry hibiscus that are currently setting fruit, and anything in pots will be relocated. The Cranberry hibiscus will usually die back and come again, but the seed pods are not quite mature enough to be picked yet, so the ones in pots will have to be protected.

tomato frost protection

It will be a test of the time for many Florida gardeners, especially those of us in North Florida, and we encourage everyone to prepare as much as possible.

How to Protect Plants from Freeze:

  • Plant between structures
  • Create microclimates
  • Plant cold-sensitive plants in pots, so you can move plants to safety in case of frost.
  • Plant cold-sensitive plants close to your home.
  • Keep your tropical fruit trees pruned small. 
  • Take cuttings of plants and trees and start indoors for spring planting
  • Cut down plants, if they get frost damage, but give them time to recover first. 
  • Water before and after a freeze
  • Use bulb Christmas lights to warm up trees.
  • Add bottles with water (not completely full) inside your frost protection 
  • A tree canopy can help protect the plants below it against frost and hard winds.
  • Mulch well with woodchips, leaves and hay (make sure it is not contaminated).
  • If you cover with plastic, make sure to remove the plastic in the morning to prevent burns. 
  • If your plants suffer frost damage, give them time to recover. This is especially important for bananas and papayas. We usually leave our bananas alone until the chance of frost has passed, and then we cut off damaged leaves, but we leave the trunks intact. For papayas, we will assess where the damage is, and cut off at an angle below the damaged trunk. 

In addition to providing protection in the shape of plastic or sheets, we also encourage you to take cuttings to start inside. We will be taking cuttings of all of our tropical spinaches and starting them inside to make more plants and potentially to replace any plants lost to a freeze. As we like to experiment, we will make sure we leave some plants outside of the frost protection are, if we have more than one plant, just so we can see how these plants manage against the frost.

How to protect plants from freeze

We are lazy gardeners, but we are not foolish gardeners, and while we aim not having to put any plants to bed, this year the reality is that many of our young fruit trees and tropical spinaches need protection, especially against an artic front with temperatures as low as 25 degrees, something we have not personally experienced with our tropical plants. 

This year all I want for Christmas is for the temperatures to stay above 32 degrees F.

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