Growing Blueberries in Containers
Blueberries can be easily grown in containers and flower pots, just be aware of blueberries specific needs regarding soil, nutrients, moisture, sun exposure etc. When grown properly, even small varieties can yield impressive amounts of these healthy fruits per individual plant.
Containers and Pots For Blueberries
Although blueberries have relatively shallow root system, one has to use larger containers and pots. Pots with diameter of at least 50cm (20 inches) are recommended and if one is using rectangular containers, they should be at least 35-40cm wide (14-16 inches) with plants being spaced apart at least 40-50cm (16-20 inches).
Of course, these sizes and distances depend on plant sizes and for container cultivation, low-bush type of blueberries are preferred types (for example, Sunshine Blue, Patriot and Top Hat varieties). If one has room for larger containers, feel free to choose blueberry varieties that can grow up to, or even more than 1.8m (6 feet).
However, for small gardens and similar locations, small(er) varieties are recommended.
Containers and pots for growing blueberries should have enough of drainage holes, since blueberries prefer moist, but not soggy soil. In heavy, soggy soils, root rot can develop and kill the plants.
Blueberry Soil Mix - How To Make Acidic Soil
One of the specifics when growing blueberries is their acid soil requirement. They will grow in soils with pH between 3.5 and 6.5, but they prefer soils with pH between 4 and 5.
And this can be sometimes really hard to achieve in home gardens for longer period of time. But, when growing plants in containers, one can choose and prepare soil for that type of plant specifically - in this case, blueberries.
There are several ways one can prepare proper soil for blueberries. One of the simplest ways is to mix two thirds of ordinary potting mix and one third of potting mix designed for plants like azaleas, rhododendrons, camellias, hydrangeas etc. or one third of peat moss. Also, adding pine bark, humus and similar organic matter can help in keeping pH levels in optimal 4.5 - 5 range.
One similar blueberry soil mix recipe:
- three fifths of ordinary potting soil,
- one fifth perlite,
- one fifth of pine bark, shredded, at most 6mm (0.25 inch) in size.
Perlite is great for keeping the soil well aerated and the pine bark adds organic nutrients and keeps the soil acidic.
Blueberries will suffer mineral deficiencies in higher pH soils - especially will suffer from iron deficiency as their ability to absorb iron decreases with higher pH. Iron deficient blueberries have yellow leaves, grow slowly, are prone to diseases and have very low crop yield, if any.
Blueberry soil mix should keep moisture well, but also be well aerated and any excess water should be able to drain away easily. Also, adding humus and pine bark mulch enriches soil and keep acidic level in check.
Fertilizing Blueberries in Containers
Blueberries don't require plenty of nutrients, however, when fertilizing them, one has to try to keep pH levels around 4.5 - 5.
Use of organic fertilizers is highly recommended: compost, humus, cottonseed meal, feather meal and similar. Also, when using artificial fertilizers, choose fertilizers for acid loving plants - such plants prefer nitrogen in ammonia form (NH4), while typical fertilizers have nitrogen mostly in a nitrate form (NO3).
It is recommended to add fertilizers twice a year. However, it is perhaps better (at least, I like it that way) to add smaller amounts of fertilizers more often, even on monthly basis. This will keep nutrient levels more or less constant and adding acidic fertilizers will keep pH level where it should be.
If possible, use more expensive NPK fertilizer optimized for berries with gradual (slow) release of nutrients – such fertilizers feed the plants up to 4 months and help with keeping pH around 4.5 - 5.
Watering Blueberries in Containers
Blueberries require between 3 and 5 cm (1-2 inches) of water per week. Of course, during summer heat, water them more often - almost on a daily basis. Also, positioning the plants to be in half shade during summer heat can help, just be sure to move plants back on full sun positions after the summer is gone.
The hard water reduces the acidic level of the soil and makes it more alkaline (pH rises), inhibiting the uptake of iron and other nutrients by the blueberries - it is good practice to check pH levels of the soil mix in containers regularly, if possible on a monthly basis.
Pollination and Other Issues
Although some varieties of blueberries are self-pollinating, it is always better to have at least 3 blueberry plants for pollination and keep them close to each other. Also, having different varieties can extend blueberry season significantly.
To protect blueberries from birds, cover the plants with light net few weeks before fruits are ripe.
Root protection in containers - when growing on garden soil patch, roots are protected by soil layer from sun heat and winter cold, but when growing in containers, roots come in contact with inner side of containers. During winter, cold can damage roots in the containers - if possible, put containers away from cold winds and prevent them from freezing. When choosing containers and pots, be sure to stay away from dark colors - such colored containers can reach rather high temperatures during summer and can damage the plant inside, plants that come in direct contact with them and can even cause burns on humans and pets!
Growing blueberries in containers, long story short:
- choose pots and containers according to the size and number of your plants,
- choose varieties according to your location,
- soil must be acidic, should keep moist well, but also it should be well aerated,
- use organic fertilizers and fertilizers with gradual release of nutrients,
- water regularly, just be sure that any excess water can drain away,
- birds like blueberries, so be sure to protect blueberries from them.
For more on growing blueberries, feel free to check How to Grow Blueberries article.