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Question of the Week © 2017 Mike McGrath
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Growing Fruit in Containers on a Deck
Q. My kids and I want to grow fruit on our deck. I was thinking of strawberries and blueberries. We get plenty of sun and I'm just wondering what type of pots to use and when to start planting. I looked online for a few tips but they vary. Any direction on this would help tremendously.
---- Matt "in a townhouse outside of Philadelphia"
A. You don't know the half of it, Mattski! There's a huge difference between growing annual (i.e.; one season life span) plants like tomatoes and peppers in containers and long lived perennial fruits like blueberries (or short-lived ones like strawberries). Although both types of plants are relatively easy to grow with their roots tucked safely in the ground, it can be very difficult to grow fruits—heck, any kind of perennial—in containers in cold-winter parts of the country, especially up on a deck.
First, there's the whole issue of protecting the pots over the wintertime. And then there's the complication that most fruits have what's called a 'chilling requirement"; a certain number of hours that they must be exposed to temps below 45 degrees F. over the winter. So these fruit plants need to be outside to experience a chill, but any plant left outside in a pot over a wretched winter can freeze and die, especially if the pots are small. (The smaller the pot, the greater the risk of death by frozen roots.)
So what's a dad to do?
My first suggestion is going to be a little unorthodox—make the fruits citrus, like the famed Meyer lemon and the miniature orange and lime trees that are meant to go outside in the summer and be brought inside to a sunny, well-insulated South-facing window when the weather starts to get chilly. Then you get to grow fruit with your kids year-round!
(Yes, this is cheating. But "cheaters always win". Remember that, kids! )
So, no hope for berries?
Oh there's hope—even a good chance of success if the conditions are right and dad is willing to do somewhere between a little and an enormous amount of extra work. Now, he says that this deck gets "plenty of sun". That better mean at least eight hours a day. The fruits in question—indeed, most fruits—are sun-hungry crops. So let's assume enough sun.
We'll start with the blueberries. One of the secrets of growing perennials in pots in climates with real winters is to choose plants that are rated for survival in arctic areas—typically you want plants that are hardy down to USDA Zone 4; and Zone 3 would be even better. Low bush blueberries—the types that grow wild in the far North—are super-hardy; and their low growing habit would make them perfect for something like growing in a half-whiskey barrel.
…Which would also meet the 'big container' rule; just be aware that you often have to drill your own drainage holes in the bottoms of these monster containers—and the wood is thicker than I am. (That's thick!) But they are the most winter-hardy containers I know of.
We're also going to protect the plants over winter. Especially if the containers sit towards the far end of the deck and are exposed to cold winds. It would be much better if they could stay in a protected corner close to the house and out of the wind; but the areas of the deck that get the most sun are going to determine placement. Sun trumps all here.
Either way, I'd drape the containers with a lightweight row cover fabric after the leaves drop in the fall, and then switch to a heavyweight row cover during the worst of winter. If Dad wants to grow the much taller highbush blueberries, he'd have to use smaller containers that he can roll up against the side of the house and cover with shredded leaves over winter. (C'mon dad—don't be a wuss!)
Just be aware that it'll take a couple of seasons for the plants to grow big enough to produce a good number of fruits. And blueberries require a highly acidic soil, so you'll want to fill the containers with half milled peat moss (which is highly acidic); and make the other half equal parts of a soil-free mix and compost.
And strawberries? As we explained in a previous Q of the Week, there are several types. I would avoid the classic Junebearers here, as they take a year to establish and then only fruit once a season, which is fine in a big garden but not in a limited space situation. Everbearing and day-neutral types produce fruits their first year and have longer picking seasons. And no matter what type, strawberries are tons o' fun for kids; you buy big tangles of bare root crowns that you have to soak in water and then pull apart to plant.
Care: Strawberries want a naturally rich, well-draining soil; so half compost and half soil-free mix in their containers. And make sure the containers drain really well. Same winter protection as blueberries. Or don't worry about protecting them and buy a new batch of crowns every Spring, just like people do with tomatoes.
And before we leave, I must put in a plug for the little alpine strawberries I love so much. My little flavor bombs! Alpine berries are tiny, but explode in your mouth with indescribable flavor—and the plants are very cold hardy. Start them from seed in the Spring and you'll get some fruits the first year. Then you'll enjoy more of the little taste explosions every season as the clumping plants get older and more productive.