Brr ...cold protection strategies part 1
Mini-greenhouses for your plants
Many tropical trees only bloom once. If you want to have a bountiful harvest next year and save your tropical and subtropical trees from potential death by cold, here's what you need to do:
~Cover your plants with a frost cloth. This can be purchased at big boxed stores and online. Heavy sheets, blankets, or plastic pots can be used as well. Make sure the covering isn't too heavy that it breaks the branches. If this is a concern, construct a bamboo or PVC structure as a mini-greenhouse.
~Make sure your coverings are secured to the ground tightly and cover the whole base of the trunk. If you leave the trunk exposed, it's like wearing capris pants out on a freezing night. Those calves freeze! Either use stakes, rocks, or bricks to weigh down the edges of your covering.
~If your tree is too big to cover, you can still ensure the freeze damage is less harmful by covering the lower trunk to protect the graft union.
~Remove the covering the following day once the temperatures have reached back into the 50's.
~If you know you're going to have multiple days in a row of below-freezing temperatures, you can leave your plants cozy under their frost blankets. Check on your coverings daily to make sure they're still secure.
List of edible plants you should cover
Perennial edible spinaches and tree hibiscuses
Non-Mediterranean herbs: things like Mexican oregano, toilet paper plant, tulsi basil, lemongrass etc
Warm annual vegetables, herbs, and flowers(tomatoes, eggplant, peppers, squash, basil, sunflowers, zinnia, etc)
Subtropical and tropical fruit trees:
~Mango, starfruit, soursop, sugar apple, cherimoya, banana, lychee, longan, avocado(young,) jackfruit, papaya, Barbados cherry, cherry of the Rio Grande, grumichama, guava, citrus, Mysore raspberry, canistel, strawberry fruit tree, black sapote, white sapote, macadamia (young,) passionfruit, akebia, etc
No need to cover hardy annual vegetables and herbs (brassica family, alliums, garlic) AND temperate fruit trees* (mulberry, peach, plum, nectarine, quince, Asian pear, pear, olive, fig, loquat, persimmon, elder, blackberry, grapes, blueberry, che, mayhaw, etc.
*Unless these trees have fruit on, then the young fruit will need to be protected from the frost.
covering with water
~Running water over fruiting trees like citrus and peaches is a common commercial strategy for fruit protection during below-freezing events, but we find it tricky for homeowners to accomplish well with home irrigation systems. If you're a commercial grower or farmer, then we recommend this strategy.
~Once you start to develop a certain size system, it can be a great burden to cover all of your tropicals in a freeze event. Unless you're a farmer or have very special grafted varieties, we suggest using the die-back strategy for some of your edible plants. The die-back strategy can be thought of as our "winter. These freezing events, just like winter up north, contribute many beneficial services to the health of the overall ecosystem. They help knock back bad bug pests cycles, slow or eliminate the spread of problematic species in conservation lands, and can sweeten the fruit and leaves of many of our favorite crops. The Caribbean fruit fly and papaya wasp, a bane to gardeners in the subtropics, is knocked back by these types of freezing events. Rejoice in balance!
What is a die-back strategy?
Let some tropical plants "die-back" or be pruned to the ground by the freezing event. This may look like armageddon but as long as these are mature (3-5-year-old trees or shrubs for most species,) then they will regrow in the spring and continue to produce abundantly the following year. Species like katuk and other perennial greens, and fruit trees like starfruit are good candidates for this strategy*.