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With this year's less than normal winter weather, I have been giving some thought as to planting non-hardy tropicals in pots and then planting them directly into the garden this year. I have heard people mention having done so themselves. If I choose to go this route, I have a few questions for those who have done this before.
1) I have various sizes of growers pots which the local nursery let me take home from their discarded pile this summer. Would these be good pots to use?
2) What would be the best type of potting soil to use? Would it be one of Al's special potting mix blends which would be catered to each type of plant?
3) For tropicals such as non-hardy Hibiscus, what size pot would be best?
4) Should I lift them and bring them inside each winter regardless of frost or freeze warnings? Or should I leave them in the ground and only lift them *if* there is a frost or freeze warning?
2) Hydrologically speaking, what you're creating are mini raised beds, and water will behave differently in those beds than in conventional containers. For that reason, it's not necessary to work as hard at making sure aeration is adequate. As long as the soil the pots are in drains well, the earth will act as a giant wick and eliminate your perched water concerns, so you can use more water-retentive soils for your app.
3) The bigger the better - you can't over-pot using the method you described, which is a minor variation on pot-in-trench growing.
4) If the roots don't freeze, you can cut the plants back hard & they will produce basal sprouts.
Al, thanks for your response. But I have a follow up question regarding your answer to #4.
How am I supposed to know whether or not the roots have frozen? Would I need to lift the pot from the ground & remove the plant to inspect the roots?
Normally, in the previous 7 years, our winters have been so mild that tropical Hibiscus lived fine in pots outside in winter. Even the few that died back during one of our rare below freezing days, began to grow once the weather started warming up. However, due to a surprising twist this winter, we were visited by the polar vortex, and received a 2 day mix of sleet and ice, & a few days below freezing at other various times, which is why I decided to pose this question.
Just in case, we experience another surprising wintry twist next year, would you suggest lifting the pots of Hibiscus & bringing them inside or just use really good protection/covering for them?
By the way, this year is my first year using your fast draining potting mix for the plants I did pot up and bring inside for winter. Like you, I don't mind having to water everyday. I have to say it is awesome knowing my plants' roots are not suffering, especially the ones who spend the winter in the cool garage (where temps can range from 49 to 65 degrees) under fluorescent lights. In the past, their soil would take so long to dry during lower temps, but this year, with your mix, I don't have to worry! No rotting roots this winter! Woohoo!
How am I supposed to know whether or not the roots have frozen? The plant will be dead, fine roots will have decomposed or will be mushy, and in mature roots the epidermis and cortex will easily slip off where they interface with the endodermis. Would I need to lift the pot from the ground & remove the plant to inspect the roots? If you leave the plant out all winter, you can physically inspect the root mass to see if it's viable, or you can wait for the onset of growth. Hibiscus in the ground won't do much until the soil warms to well above 60*, so be patient.
Just in case, we experience another surprising wintry twist next year, would you suggest lifting the pots of Hibiscus & bringing them inside or just use really good protection/covering for them? If you want to be certain, lift & bring indoors. They'll winter well, almost dormant, if you stick them in a cool dark place and allow them to go quite but not completely dry. If you're a risk taker, evaluate the risk & take your chances. I'm not being snarky, just pointing out what's probably already obvious to you.
Glad you like the fast-draining and well-aerated soil program. It sure makes life easier. ;-)