Growing blueberries in containers

Growing Blueberries in Containers

With just a little effort, home gardeners can successfully grow blueberries in containers.

Vijai Pandian, UW-Extension Brown County and Rebecca Harbut, UW-Madison Horticulture
Revised: 12/9/2010
Item number: XHT1196

The blueberry is a wonderful fruit rich in vitamin C, dietary fiber, and vitamin E. Due to its popularity, there is a growing interest among gardeners to plant blueberries in backyard gardens. One of the most critical factors for successful blueberry production is providing an ideal soil pH in the range of 4.5 to 5.0. This is a challenge in many parts of Wisconsin where soils are typically too alkaline (i.e., the soil pH is too high – above 7.0) for blueberries. Highly alkaline soils that are clay or high in organic matter can be amended by adding large amounts of sulfur to lower the pH, but will require repeated amendments over time to maintain an ideal pH. Therefore, attempting to lower soil pH may not be a viable option for backyard gardeners who have an elevated soil pH. An alternate option for producing blueberries is to grow them in a container filled with an acidic soilless growing medium.

How do I prepare the growing medium? To prepare an acidic soilless growing medium, use a mix of one part sphagnum peat moss and one part shredded pine bark. Another growing medium that works well is a mix of two parts coir (shredded coconut husks used in the greenhouse industry), two parts sphagnum peat moss and one part perlite. Mix all ingredients well. Fill a five-gallon container with whichever mix you decide to use, and plant a single blueberry plant in the container. As the plant matures, repot it in a larger container (e.g., a 16 or 20 inch pot) or in a barrel, once again filled with the acidic soilless growing medium of your choice.

What cultivar of blueberry should I use? When selecting blueberry plants, choose half-high bush cultivars as they are hardier in Wisconsin, and are relatively short in stature. Some popular half-high cultivars recommended for Wisconsin (i.e., hardy in zones 3 though 5) are ‘Northblue’, ‘Northsky’, ‘St. Cloud’, ‘Polaris’, ‘Chippewa’, ‘Northland’, and ‘North Country’. You can also select low bush blueberry cultivars such as ‘Top Hat’ (hardy to zone 5) for container production. Low bush cultivars have a dwarf (i.e., maximum 12 inch height) and spreading growth habit and typically produce smaller fruit. Most blueberry cultivars are self-fruitful and do not require another cultivar for cross pollination (‘St. Cloud’ and ‘Polaris’ are exceptions). In general however, growing more than one blueberry cultivar will improve pollination and enhance yield and berry size.

How much water will my blueberry plants need? When growing containerized blueberries, closely monitor growing medium moisture levels. Blueberries do not like to have ‘wet feet’, but insufficient moisture can also be a problem. Therefore, try to maintain a moist, but not wet/soggy, growing medium. Frequent, light watering is ideal, with an occasional ‘drench’ to eliminate soil salts. Mulch the soil surface with two inches of pine bark or chipped hardwood bark to conserve moisture. Avoid using black containers for planting blueberries as such containers absorb heat leading to more rapid moisture loss. If using drip irrigation, place two emitters in each pot on either side of a plant. Another way to reduce heat stress and water loss is to bury containers in the ground. Buried containers can be left in ground for over-wintering. Water quality is as important for growing blueberries as the composition of the growing medium. Collected rainwater is ideal for watering, and typically is not as ‘hard’, nor has as high of a pH as well water.

How do I overwinter my blueberry plants? Because containers do not provide adequate insulation from the cold, be sure to protect container-grown blueberries during the winter to prevent root damage. In mid- to late October, bury containers in the ground at a site where snow is likely to accumulate and where plants will be protected from cold winter winds. Mulch the soil surface with four to eight inches of straw in mid-November or cover the bushes with burlap. Prevent rabbit damage by placing chicken wire fencing or hardware cloth around the bushes. During early to mid-spring, remove containers from the ground and place them in full sun. Alternatively, containers can be left buried in the soil as long as the containers have proper drainage holes and the site where the containers are buried is well drained and exposed to full sun.

How do I properly fertilize my blueberry plants? A combination of supplemental liquid and slow-release acid fertilizers is recommended. Avoid overapplying fertilizers, as blueberry roots are sensitive to fertilizer salt injury. Apply slow-release acid fertilizers (e.g., elemental sulfur) four weeks after planting in the first year and then top dress the growing medium surface lightly the following spring. Make sure you follow the recommended rates described on the fertilizer label.Slow-release fertilizers will typically need to be supplemented periodically (usually every two weeks) with more fast-acting acidic liquid fertilizers (e.g., Miracid) when the blueberry plants are actively growing during the spring through mid-summer.

For more information on growing blueberries in containers: Contact your county Extension agent.

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Tags: container gardening Categories: Fruit Care

Containers planted with spring flowering shrubs that also deliver a hefty punch of autumn color are a stylish addition to the porch or garden. But if the shrubs you choose to grow in containers are blueberries, they’ll also serve-up sweet taste.

Growing perennial fruit where you normally place zinnias and coleus, may seem a bit of a stretch, but consider the appeal of blueberry’s three-season show with the added benefit of the highly nutritious berry. Blueberries are an extremely attractive plant and are very well suited to container growing.

Blueberries are among the easiest fruits to grow. They are relatively pest and disease free. But they can be finicky about a couple of things. Blueberries love acidic soil and they need moist and well-drained growing medium. A big benefit of growing them in containers is that you can easily control each of these soil conditions.

In a container, achieving the acid levels you need is easy. Start with an acid potting soil or a mix of coir, some organic matter – like leaf mold – and condition the mix with an organic soil acidifier. Coir is a good choice for blueberries because coir holds water longer. It’s also good to routinely feed the plants with an acid based fertilizer or organic cottonseed meal or feather meal that will also add acidity to the soil. Fertilizers designed for azaleas, rhododendron, hollies or evergreens will work for blueberries. The best pH for blueberries hovers between 5.0 to 5.5. Feeding with fertilizers designed for acid plants will keep your potting soil near that range, but if you’re concerned and want it to be exact, soil pH testers, like our electronic soil tester, are available.

Choosing the right variety of plant and the right size container is important. Look for shorter growing varieties. Some excellent choices are Blueberry ‘Top Hat’ which tops out at around 2 feet tall sporting white flowers and feisty orange fall color, or three-feet petite Blueberry ‘Sunshine Blue’ with pink flowers and burgundy fall foliage or even the slightly taller Blueberry ‘Patriot’ with subtly pink-tipped white flowers and orange to red autumn tones. Most blueberries need another type of blueberry nearby for pollination. Check this with each variety. Blueberry, ‘Sunshine Blue’ is self –pollinating.

The container should be large enough to balance the size of the shrub. Think five gallons of soil with a container diameter at nothing less than 24 inches. There are a couple of design approaches you can take. You can start with a slightly smaller container and allow the plant to grow until it fills it, then transplant the blueberry into a larger container. A fun way to go, is to plant in the largest container your space and pocketbook allows, and fill in around the blueberry with annual flowers for a classic container look. Contrast the blueberry’s warm, fall foliage color with spunky fall flowers like asters and mums. Depending on the container, consider planting more than one blueberry together. Pretty and easy in pots, blueberries do require a little extra watering consideration.

Blueberry roots grow close to the soil surface. Watering them is a bit counterintuitive to the seasoned garden because frequent shallow watering works better than deep soaking watering. Containers dry out quickly, so it’s important to routinely water. Berry size and blossom formation will be improved with adequate water. Be careful, overwatering can also damage the roots.

With a little attention to acidity and water, blueberries thrive in containers. Containers become more than ornamental. They serve the extra function of providing food. It’s not often that you can do something simple that simultaneously bumps-up the impact of your gardens, while producing a berry that can impact the quality of your health.

Growing blueberries

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Planting

Remove the blueberry plant from the original pot you purchased it in within two weeks from purchase. For the most optimum potting mix for your blueberry, combine 50% coarse pine bark (20 – 25mm in size) with 50% of a premium quality Camellia/Azalea potting mix. This provides a well aerated potting mix which will extend the life of your blueberry in a pot considerably. Do not tease the roots of the plant before planting as this will severely affect the plants establishment. When transferring your newly purchased blueberry into a larger pot ensure the top of the potting mix remains at the level it was at in the pot you are moving it from. Add a layer of pine bark to the top of the pot to protect the surface roots and minimise moisture loss from the potting mix.

Why Premium potting mix?

Premium potting mixes are the first choice when you want the very best for your plants. They have a greater water-holding capacity, contain added nitrogen and other plant nutrients, and remain at peak performance for a longer period compared to cheaper alternatives. They are a worthwhile investment, especially for those superior plants which you need to keep looking spectacular as decorative specimens. Premium potting mixes are marked on the bag by Red Standards Marks ‘ticks’

While blueberries require a pH of 5.0 – 5.5 most Camellia/Azalea potting mixes are already in this range, however it is good idea to check it anyway. A pH soil test kit purchased from your nearest garden centre or hardware store is easy to use and is ideal for checking soil pH over your entire garden area. Add a good quality 3 month slow release fertiliser to your potting mix and mix in well if it is not included in the potting mix purchased. PlantNet recommends these potting mixes above to help keep the pH low/acid and to provide a well drained and open potting mix for good blueberry root development. Blueberries produce masses of fine roots which mat together when growing well. Without a well aerated potting mix (using pine bark) all blueberry varieties will only have a life of around 2-3 years in pots. This premium potting mix should extend the plants life well beyond this.

How to Grow Blueberries

Blueberries bring a unique combination of delicious fruit and striking, year round ornamental beauty to the garden and landscape. They’re relatively easy to grow and require minimal care. By following just a few basic steps, your blueberry plants will thrive for many decades and provide you with abundant fruit every year. We highly recommend you read the Blueberries Simplifed section of our site for a primer on selecting varieties. Below are some basic tips to help ensure your success with blueberries:

Site Selection and Preparation

Select a sunny location with well-drained soil that is free of weeds and is well-worked. It’s best to locate your blueberry plants in an area where irrigation is readily available as best results will be achieved by keeping the root zone moist throughout the growing season.

Where the soil is not ideal or marginally-drained, raised beds are an excellent option. Blueberries also do well in patio containers and offer a great way for apartment and condo dwellers and those with little or no yard to enjoy blueberries.

Blueberries prefer acidic soils. A fail-safe way to grow blueberries in almost any soil is to incorporate peat moss into the planting medium. For planting directly in the ground, work up a planting area approximately 2½ feet in diameter and 1 foot deep for each plant. Remove 1/3 to 1/2 of the soil. Add an equal amount of pre-moistened peat moss and mix well. (One 4 cubic foot compressed bale will usually be sufficient for 4-5 plants.) For raised beds mix equal volumes peat moss with bark (not cedar or redwood), compost or planting mix. Talk to your local garden center. They’re experts in your area and can best advise you on soil amendments.

Spacing

Blueberries can be planted as close as 2 – 2½ feet apart to form solid hedgerows or spaced up to 6 feet apart and grown individually. If planted in rows, allow 8 to 10 feet between the rows depending on equipment used for mowing or cultivating.

In most areas, it is ideal to plant in the fall or spring although in many regions you can plant year round.

If you purchased containerized blueberry plants, remove from pot and lightly roughen up the outside surface of the root ball. Mound the plant’s top soil about 1/2 inch higher than the existing ground and firm around root ball. Then mound soil up along sides of exposed root mass and water in well.

Mulching

Blueberries do best with 2-4 inches of mulch over the roots to conserve moisture, prevent weeds and add organic matter. Bark O Mulch, acid compost, sawdust and grass clippings all work well. Repeat every other year. Do not use bark or sawdust from cedar or redwood trees.

Pruning

It’s a good idea to allow blueberries to get established before allowing them to bear fruit. If you start with smaller plants, simply remove most of the flower blooms as they appear. In future years, blueberry plants should be heavily pruned each year to avoid over-fruiting which results in small fruit or poor growth.

In our three decades of experience at Fall Creek, we know that one of the biggest mistakes home gardeners make with their blueberries is lack of pruning. We assure you that aggressive, annual pruning will result in healthier, more vigorous plants and more prolific fruit production. Here are some simple tips:

Remove low growth around the base.
Remove the dead wood, leaving bright colored lateral branches. Cut out any short, discolored branches.
Continue pruning until you have removed 1/3 to 1/2 of the wood out of your plants each year. Remember, this will promote growth and berry production so prune away!

Fertilizing

Once established, blueberries like acid fertilizers such as rhododendron or azalea formulations. (Ask your local garden center for recommendations.) Take care when fertilizing, since blueberries are very sensitive to over-fertilization. Follow label instructions.

It’s ideal to fertilize once in early spring and again in late spring. Be sure to always water thoroughly after fertilizing. For organic fertilizers, blood meal and cottonseed meal work well. Avoid using manures as they can damage the plants.

A NOTE TO HOME GARDENERS: We regret that we don’t have staff available to respond to home gardening questions on the phone or by email. If you have more questions, please contact your local garden center or extension agents. They’re the experts in your area.

Blueberry plants are compact deciduous shrubs, which drop their leaves in winter. They bear white bell-shaped flowers in spring, followed by the clusters of fruit which gradually ripen to deep blue through the warm months of the year. In growing terms, they prefer a sunny spot (though some light shade during the day is fine) and they do best in acidic soil or potting mix.

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Pot Growing Basics

1. Choose a dwarf variety such as ‘Blueberry Burst’, which grows only about 1m high and 75cm wide. It’s also self-pollinating, which means you don’t need to have another bush nearby.

2. Select a pot which is about 40cm wide and deep, and fill with an acidic potting mix – any of the mixes formulated for azaleas and camellias are suitable.

3. Position the pot in a sunny location before you plant, as it will be heavy to move after planting. Remove the blueberry plant from its plastic pot, gently tease out the roots and position it so that its surface sits a couple of centimetres below the lip of the pot. Backfill with more potting mix, firm down and water in well.

4. When flowers and fruit start to form, feed regularly with a soluble fertilizer, such as Yates Thrive Strawberry & Berry Fruit Liquid Plant Food. Keep the plant well watered through the summer months.

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Blueberry Growing Guide

Blueberries are an increasingly popular addition to Kiwi backyards. A fruit high in antioxidants, easy to grow year-round, with attractive foliage and suitable for smaller spaces, it’s easy to see why they are a superfood of the garden!

The blueberry is a good example of a fruit taken from the wild and transformed into an easy to grow edible delight. They thrive in New Zealand’s varying climatic conditions.

Blueberry plants grow naturally as a bushy shrub, up to 1.5m tall or can be pruned to keep at 1m tall. The blueish-grey-green leaves make a striking show in the summer garden. Flowers appear in clusters of pink and white, which are attractive to bumblebees.

Edible hedge

Blueberries make a wonderful edible hedge. Plant around 1m apart to form a delicious and attractive edible hedge. Varieties which go well together to create a hedge include: Misty and Marimba; Climax and Tifblue; Bluecrop and Dixi.

Prepare

Blueberries can be planted year-round. The better the soil, the better your berries will grow. Blueberries prefer a free draining, more acidic soil with a high proportion of organic matter. They are best planted in a sheltered, well drained position in full sun.

If you are starting with an existing garden bed dig in organic matter like Tui Sheep Pellets and compost to your soil. Then you can add a layer of Tui Strawberry Mix or Tui Peat Plus to the planting area. If planting in pots and containers fill with Tui Strawberry Mix.

Choosing a variety

Consider your climate when choosing a variety as blueberries love a certain amount of chilling time. Select a plant that will suit your environment. Most blueberries are at least partially self fertile but planting a combination of varieties of the same type will ensure good cross pollination and therefore good cropping. Different varieties also have different foliage colours in summer and autumn, which look really stunning.

Top varieties to plant include:

Blueberry Northern Highbush – varieties suited to the more temperate regions of New Zealand. These varieties flower in mid spring and produce berries from December to February.

  • Bluecrop
  • Dixi
  • Duke

Blueberry Southern Highbush – varieties best grown in warmer areas of New Zealand as they have a low chill requirement. Fruiting from later spring to February.

  • Marimba
  • Misty
  • Petite Blue

Rabbiteye – best grown in warmer areas of New Zealand as they require less winter chilling. Fruit from January through to April.

  • Climax
  • Delite
  • Tifblue

Plant

Check plant labels for individual planting instructions. The best times to plant are early in the morning or late in the day, so the plants aren’t exposed to the hot sun straight away.

Planting blueberries in the garden:

  • Soak your plant in a bucket of Tui Organic Seaweed Plant Tonic before planting and allow to drain. This will help prevent transplant shock and give your blueberry a healthy start.
  • Dig a hole approximately twice the depth and width of the root ball of your plant and partly fill with Tui Strawberry Mix.
  • Gently loosen the root ball of your plant.
  • Place the tree in the hole, and fill in with Tui Strawberry Mix, ensuring the tree is no deeper than it was in the container or bag.

Planting blueberries in pots and containers:

  • Soak your plant in a bucket of Tui Organic Seaweed Plant Tonic before planting and allow to drain. This will help prevent transplant shock and give your blueberry a healthy start.
  • Partly fill with Tui Strawberry Mix, and tap on the ground to settle the mix.
  • Gently loosen the root ball of your plant.
  • Place your tree in the pot, and fill in with Tui Strawberry Mix, ensuring the tree is no deeper than it was in the container or bag.

Don’t let your blueberries produce too many fruit when young. They tend to overfruit when young, so not enough energy is put into root and branch development.

Nourish

Feed your plants and they will feed you. Replenishing nutrients used by your blueberries ensures they will grow to their full potential. For blueberries planted in garden beds feed in spring and summer with Tui Citrus Food, it has extra potassium for flowering and fruiting. For blueberries in pots and containers use Tui NovaTec Premium fertiliser.

Water to keep moist throughout the growing season, though don’t let the plant get too wet or too dry. Well watered, well nourished blueberries will have a better chance of keeping insect pests and diseases at bay.

Tui Tips

  • The fragile branches need care when pruning. Not all blueberries lose their foliage over winter, but if they do this is a good time to prune. Blueberries fruit on the previous season’s wood, so be careful not to remove too much of this when pruning as you will end up with less fruit in the upcoming season. Prune out any dead or diseased wood and branches that are crossing over one another to allow more light and air in.
  • Birds love blueberries so protect your bush with netting.
  • Add Debco SaturAid to the soil to prevent it from drying out in the summer months.
  • Pick the fruit that ripens first to bring on the other fruit that has yet to mature.
  • Blueberries are ideal for freezing, as they keep their shape and flavour. They can also be cooked from fresh or frozen.

For tips on growing other berries read our Berry Growing Guide >

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