Cold protection of tropical container plants

Q: I am long time customer of yours, I live in San Diego California and while the summer and Fall temperatures are warm to mild, the winter temperatures dip to a point where some tropicals die off. We are experimenting with different variations of way to heat and insulate the pots we have the tropicals planted in as a way to keep them alive during the colder winter months. I was wondering if you knew of the ideal soil temperature for these tropical in order to look their best year round. All of the heaters we have installed have thermostats and temperature adjustments so we can now keep the soil anywhere between a range of between 65-75 degrees. Any advise you can provide would be greatly appreciated.

A: This is a very interesting concept you are working with. Indeed, keeping pots/roots warm, may help a lot! We've been experimenting with cold protection for a long time - for the above-ground plant parts. For sure keeping roots protected (even with a thick layer of mulch) will benefit tropical plants during winter. In case with container plants, this may help dramatically.
The guideline is, tropical plants slow down or stop their metabolism at 65F. As long as you can keep soil above that temperature - this should work great. Of course, the higher the better.
Optimum temperature for growing tropical plants in general - 70-85F. Above 90F, metabolism stops too, unless it's a heat tolerant, desert plant.

Greenhouse in Virginia
Plumeria cold protection
Ghost Cold Protection
Seven rules of cold protection for tropicals
About Cold Protection
Cold protection - winter action for your plant collection
Tropical Treasures articles on zone pushing.

Ghost Cold Protection

Q: Has anyone ever tried using heat packs under frost blankets to protect tropical plants from frost?

A: The reality is, the heat packs used for shipping do not have enough heat capacity to create efficient warming effect. From our own experience, the best way is to use small 25W incandescent bulbs which produce lots of heat (considering observing all safety precautions and fire safety). Some gardeners use Christmas lights. See picture of our plants in the ground during a cold night. We called them Ghost Cold Protection! ;)

See more columns on cold protection:
Seven rules of cold protection for tropicals
About Cold Protection
Cold protection - winter action for your plant collection
Tropical Treasures articles

URBAN TROPICAL GARDENING:
10 secrets of successful Container Mango growing on a balcony.

Q: I live in Miami in apartment on a second floor, and I have a balcony with SE exposure. I wonder if I can grow a mango tree in a pot? Will it fruit for me? I recently moved to South Florida and I don't know much about tropical plants; but I tasted real fiberless mangos from someone's garden - it was so delicious and different from those in the grocery store. I wonder if I can have a fruiting tree on my balcony? And if yes, how do I plant and take care of it?

A: Yes, you can! Here is what you need to do:
1) Temperature. You are lucky to live in Tropics, keep it on a balcony year round.
2) Light. Position the pot in a spot with the most sun exposure. Mango trees can take filtered light too, but the less sun, the less fruit you will get.
3) Soil and Container. Use only well drained potting mix. Step up the purchased plant into next size container (3 gal into 7 gal, 7 gal into 15 gal). When transplanting, make sure to keep growth point (where roots meet the trunk) just at the top of the soil. Covering base of the trunk with soil may kill the plant.
4) Water. Water daily during hot season, but only if top of soil gets dry. If it still moist, skip that day. Mangoes (unlike Avocados!) prefer to stay on a dry side.
5) Fertilizer. Use balanced fertilizer once a month, 1 tsp per 1 gal of soil. Do not fertilize during fruiting - this may cause fruit cracks.
6) Microelements. Apply SUNSHINE-Superfood once a month. This will help your mango healthy, vigorous, and resistant to diseases. Use SUNSHINE-Honey to make your fruit sweeter.
7) Insect control. Watch for scales and mealybugs, clean with solution of soapy water + vegetable oil (may need to repeat 2-3 times with 10 days interval), or with systemic insecticide like imidacloprid only as needed (if non-harsh treatment didn't help). Most Flea shampoo for dogs contain that chemical, you may try that shampoo solution.
8) Trimming. Once potted, do not remove leaves that are discolored or have spots until new growth appears. Dark dots on mango leaves, especially in humid climate like Florida, may be signs of fungus. Treat with fungicide according to label, and remove only badly damaged leaves. Trim crown as needed after flowering and fruiting (by Fall). Train into a small tree, and you may remove some lower branches eventually.
9) Flower and fruit. Mangoes are winter bloomers with bunches of tiny flowers coming in thousands. Many of them set fruit (if pollinating insects present). Keep in mind that young trees can only bare a few fruit. Normally a tree will drop excessive fruit and keep only a few that it can manage. To save the young tree some energy, remove fruit if too many and leave only 2-3 for the first year. It will pay you next year with more abundant crop.
10) Variety. Last but not least: Choose the right variety for container culture! Pick from "condo" dwarf varieties such as Icecream, Nam Doc Mai, Carrie, Cogshall, Julie, Fairchild, Pickering, Graham, Mallika, and a few others - check out Mango Chart pdf and full list of our Mango varieties.

How to feed a Mango tree...
and to grow a Dwarf Mango

Q: My mango trees that I bought and planted last august now have fruit. I bought 2 types of fertilizer from you and never used it. Should I use your fertilizer now?

A: It is a perfect time now to fertilize your plants as they start active growth. For mango trees, we recommend liquid fertilizer Sunshine Booster - Mango Tango. It is formulated for Mango trees, especially for container grown. It improves quantity and quality of flowers and ability to set fruit, reduces bud-flower-fruit drop. Can be used as often as with every watering. For best results, use in combination with Sunshine Honey and Sunshine Superfood plant supplements. Its scientifically-balanced stable formula is organic Amino-acid based and has NO EDTA chelators to eliminate nutrients lockup; it does not affect crop taste.
Additionally, you may use slow-release granulated fertilizer Mango-Food once a month during hot season only. Dosage: 1 teaspoon per each gal of soil. Water-soluble fertilizers can be also used, however, those are usually EDTA-chelated which is not as efficient as Amono-acid based Sunshine Boosters and may create nutrients build up, especially if overdosed in containers.
For in-ground mango trees, you may use all the above, and slow-release granulated fertilizer can be applied in larger quantities: spread a handful around the drip line.

Remember that only liquid Sunshine Boosters can be applied year around. With other fertilizers, you need to be careful not to overdose, and apply only during hot weather (when night temperatures are steadily above 65F).

Q: I received the Ice cream mango tree in great condition (thank you for the ingenious packing job) on Wednesday and have planted it in a pot slightly bigger than the root ball. I plan to grow the tree on my front porch, so how big a container should I ultimately use when the tree outgrows this pot? How big a container does it need to fruit? I hope to keep it around 6-7 feet high, if possible. I live in Hawaii.

A: Ice Cream mango is a perfect variety for container culture, and it should be happy in Hawaii. You did everything right. Keep it in this small pot for now and wait until it starts vigorous growth in Summer. Once it starts growing (and you will notice roots growing too, sometimes they try to grow through the holes in the bottom of the pot), then it's time to step up into a bigger container (7-10 gal). Eventually you may use container size as large as 15 gal. Ice cream mango is slow growing and compact, and you will be able to maintain it under 7 ft with very minimal pruning if any.