Why would you consider growing blueberries in containers?
There are several good reasons.
And in fact, planting your blueberries in containers might be the easiest way to grow blueberries in your location (and the only way in some locations).
If you live in a location where the soil is far from ideal for blueberries, you’ll probably find growing blueberries in containers to be both easier and more successful than growing them in the ground.
Though certain varieties of blueberries can attain the size of small trees, their root systems are much smaller than most trees.
The root systems of blueberry plants tend to be shallow and compact. This makes blueberry plants far more tolerant of the relatively restrictive confines of a planting pot or planting barrel.
So if you've been told that your soil is no good for growing blueberries, don't despair. You can still look forward to harvesting your own homegrown blueberries. You'll just need to run an end-around past your blueberry-unfriendly soil.
Let's begin by choosing the right container for your plant.
There are several different types of blueberries. At maturity, the largest of these might soar to well over 10 feet tall (20 feet, even!). The smallest, though, might just barely reach to a foot and a half.
Obviously, a cute little container that would be just fine for the little guy isn’t going to work for the big guy.
The popular dwarf variety Top Hat (which is often grown as blueberry bonsai) will do just fine in a petite 5-gallon container.
But a larger variety such as a rabbiteye or highbush needs a container volume of at least 20 to 30 gallons.
Half whiskey barrels and wine barrels are popular planters for larger blueberry varieties.
(It doesn’t have to be a real wooden barrel, of course. Plastic versions like this will do just fine.)
When selecting a container, keep in mind that if all goes well your blueberry plant should live for many years. So you’ll probably want to select a container that will hold up to years of use.
If you’re using a wooden container, it might be best to start with one that’s brand new, rather than one with its best days behind it.
Whatever type of container you select, be sure that it has adequate drainage for your blueberry plant, since blueberries are very intolerant of ‘wet feet.’
If you’re using something like a whiskey barrel that doesn’t have built-in drainage, drill some holes in the bottom – at least a half dozen. Make them good-sized holes, too, so that they aren’t easily plugged. 1/2 inch diameter holes would probably work fine.
Here are a couple of options that would work just fine for growing blueberries:
Wooden Half Whiskey Barrel
Plastic Barrel Planter
Half Wine Barrel Planter
Unfinished Half Whiskey Barrel
When you're growing in the ground, you have only a certain amount of control over the root-zone environment of your plants.
But that's not true of container growing, where you have complete control over the root-zone environment.
Take full advantage of the control you have when growing blueberries in containers by making your container soil absolutely perfect for blueberries.
You can make your container soil perfect by optimizing 3 basic criteria:
The ideal soil pH for blueberries is in the 4.0 to 5.0 range. You can assure that the pH in your container is just where you want it by making peat moss the featured ingredient of the growing media you’re using.
Blueberries love peat moss, and you’d probably do fine growing your blueberries in 100% peat. And using lots of peat moss will also provide the organic matter that blueberries love.
But mix in some peat-based potting mix along with the pure peat moss for balance.
Use no less than 50% peat moss in formulating your potting mix, and be sure to test the pH in the container before planting.
If the pH is above the 4.0 to 5.0 range, just lower the pH by increasing the ratio of peat that you’re using in the mix. (If you’d rather not do any mixing at all, you can buy peat-based potting mixes that will do the job.)
Drainage should be fine with all of that peat moss in your potting mix.
But if you want, you could add a bit of perlite to your potting mix if you wish to further facilitate drainage.
Perlite is an absolutely wonderful addition to potting mixes. It helps to assure good drainage. And yet - because each perlite grain holds water in its many tiny nooks and crannies - perlite also helps to assure a constant supply of water to roots.
How do you know if the drainage in your container is OK?
Just use this simple test: When you pour water in the top of the container, there shouldn’t be much of a delay before water is draining from the bottom.
If it takes a while for water to begin draining from the bottom, you probably need to work on your drainage a bit more.
If you're OK on numbers 1 & 2 above, you should be in good shape on this one. Your potting mix will be composed of mostly organic matter.
Just in case you're wondering, though: DO NOT add any soil to your container - not even your best garden soil.
You don’t need it.
By adding soil to your container, you’d be adding a bit of an unknown, even if you’ve had your soil tested.
Why risk adding disease pathogens and pests to the wonderfully utopian environment you're creating for your blueberries?
Your blueberry plant will do just fine with the container ingredients mentioned above. And you’ll be sure that you’re giving your blueberry plant exactly what it needs to be healthy and productive. No soil required.
If you’re growing blueberries in containers, you’ll care for them in much the same way as blueberries planted in soil. But there are a few small differences in caring for container-grown blueberries...
Blueberry plants don’t like wet soil. But they’ll also have trouble if the roots get dry.
Since the root zone can dry out much faster in a container, you’ll need to monitor the moisture level in the container a bit more than you would for blueberries planted in the ground.
The root zone needs to stay moist, but not wet. Water thoroughly when the surface of the potting mix is dry to the touch – and only then. Don’t water when you can feel moisture on the surface.
Mulch can be a great tool in helping to stabilize moisture in container blueberries, just as with blueberries planted in soil.
And because the limited volume of the container increases the risk of salt buildup and pH fluctuation, you’ll need to be a little careful about the quality of the water you use.
Low sodium water is best. Rainwater is low in sodium, and you can also collect air conditioning condensate to water your blueberries and other plants. It’s essentially man-made rain, having been squeezed out of the air by the cooling process.
And if the pH of your water is alkaline, you can acidify it by adding some vinegar (try about a tablespoon of vinegar per gallon of water).
(Note: Soil moisture meters like this one can be quite useful in managing container-grown plants.)
When growing blueberries in containers, you can fertilize them with the same blueberry fertilizers that you’d use for blueberries planted in the ground.
But you'll need to fertilize more often than with in-the-ground plants. That's because water will be cycling through your plant's root zone more frequently, and therefore leaching soil-borne nutrients out more quickly.
Plan on fertilizing about once per month during the growing season.
One other caution about growing blueberries in containers: don’t let the roots freeze.
It's true that blueberries are cold hardy plants – the most cold tolerant lowbush varieties will survive extremely frigid temperatures. But your container plants will be vulnerable to sustaining freeze damage to the roots during very low temperatures because they don’t have the protective insulating effect of the ground surrounding them.
So during cold snaps you might need to move your container blueberries into a more sheltered environment, such as a garage.
Another alternative is to dig a container-sized hole in the ground, and put your container in the hole during cold weather (or for the entire winter if you wish).
And not just in the traditional sense, either.
Sure, you can expect your container blueberries to be very productive. You can look forward to many years of harvesting plump, sweet, juicy berries.
Yes, the blueberries will be delicious, and yes, they’ll be very good for you.
But growing blueberries in containers will also provide a feast for the eyes.
Blueberries are very attractive plants, and whether you place your pots on the patio or scatter them about as attractive lawn ornamentation, you’ll enjoy the beauty they provide as much as you enjoy the bounty they produce.
Well – almost as much, anyway. Blueberries sure are yummy!