Blueberries

Varieties

Select blueberry varieties that are optimal for your growing area. Most types are self fertile and do not need pollination from another variety but if you are planting several plants then it is good idea to mix the varieties. If however you choose say early or late varieties to spread the time of picking, there will be little help with the pollination as they will flower at different times!

Site

Choose a sunny site, and test the soil pH (a test kit can be purchased from any good garden centre). Blueberry plants prefer acidic soil with a pH of 4.5 to 5.0. This is more acid than most UK soils and more acidic than your normal soft fruit soils so do not expect the Blueberry plant to do well just because the soil is good for Raspberries or Strawberry plants – it won’t! It is therefore important to check this as it is one of the most common causes for plants not growing. Mix in any organic matter e.g. manure, shredded leaf compost and grass clippings to adjust the pH. Alternatively bark is excellent to mix in to the soil, or blueberries will be quite happy to grow in 100% bark (make sure the vendor has not added any lime to it!) For a very alkaline soil then sulphur is probably the best addition you can make to the soil to bring down the pH quickly. This is difficult to do accurately on a commercial scale, let alone on a small plot for a few plants and you will need 9-12 months to get this right as often more than one application is required, so wherever possible choose the site well in advance or use a higher proportion of brought in material in order to alleviate this problem. If you do want to try sulphur, as a guide for loamy ground that is pH5.5, start with 100g/m2 and monitor the pH every couple of months. Use 200g/m2 if pH 6 to start with. The full effect will not be seen for 6 months but you should get an earlier indication of the effect.

Blueberry roots like oxygen round them, and for this reason the roots sit close to the surface. The soil should not have a high (>5%) clay content as this both blocks the movement of oxygen to the roots, but also if the soil is allowed to get wet and then dries in the sun, the expansion and contraction will break the very fine fibrous blueberry roots that are near the surface as they are not strong enough to withstand such movements of the soil. The plants will be perfectly happy in 100% bark, but this can dry out fairly quickly, so according to the type of soil being mixed, vary the % of organic matter added to give a nice fibrous loose consistency that does not get water logged when watered or conversely dries out with a few days of sunshine. Blueberries like similar soils to Rhododendrons if you are more familiar with growing those species.

Polytunnel or Greenhouse

Blueberries grow well under cover even though they are naturally a woodland species, being related to Bilberries, Cranberries and Lingonberries. There is an increased danger of the roots drying out, so a mulch to reduce evaporation and give the correct environment around the upper root zone becomes more important.

Planting

This depends on the size of the plant, but assuming plant is 30-90cm (1-3’) tall, dig a hole about 60cm (2’) deep and the same in width for each blueberry plant. Space the holes around 1m (3’) from each other in the row, and if you are planting more than one row, space no closer than 2.5m across the row. If the soil is compact in the bottom of the whole then loosen this with a fork as well. Fill 30cm of each hole back up with pine bark or a suitable Rhododendron type compost mix then plant the plant. If the plant is pot bound i.e. the roots are compact and turning round in a circle when tipped out the previous growing container, then spend a few minutes breaking up the outside of the clump to allow plenty of surface area of loose material contact with the roots. Don’t worry if this means breaking the roots as this is preferable to planting a pot bound plant, as this plant will otherwise sit in the new location and probably not show much sign of growth for at least the first year, and may be permanently stunted, while it gets used to its new surroundings. Commercially there is a small risk of infection to these broken roots but this is very unlikely to be a factor in non commercial fields.

Back fill with more bark or compost mix. Concentrate on ensuring that the area round the plant is very loose fibrous material of the correct pH as either will give problems if not correct. Make sure that the crown of the plant is at ground level i.e. don’t plant deeper or shallower than the plant was before being planted. Finally place a 75-100mm thick layer of pine bark or other organic matter in a 1m diameter circle around each plant (or 1m wide if several plants together running down a row). This will serve two purposes, the first is to suppress weed growth and the second is to maintain a damp zone near the surface where the roots prefer to grow. Move the bark away from the area of 3-5cm around the stem of the plant to maintain the planting depth, but in the case of pine bark or anything very loose this is less of an issue as air will be circulating through the mixture.

Pots

Blueberries can also be grown in pots, and this has advantages and disadvantages. The main advantage is that the cost of getting perfect soil mix is reduced and more easily controlled. The downside is that the pot is more prone to drying out if not managed well, and the roots can become pot bound if not potted on at the correct time. A typical 1 year old 30cm high plant will need a 1l pot and then transferring to a 5L pot for 2nd year then a 20L pot for the 3rd year and a 40l pot thereafter, so a very large pot is required after the first 2-3 years (unless of course you do not follow the other recommendations in this advice, in which case the plant may never grow higher than when you planted it!)

Immediately after planting you must decide if the plant needs trimming back or not. Do not be afraid to trim the plant back to 30-50cm tall as the branches on the plant when you plant it are not going to give you anything other than the odd berry in the first year and the trimming will both stimulate new growth and also reduce any transplant shock. It’s highly recommended that you should concentrate on getting the plant growing in the first year in order to maximise the wood on the plant to bear fruit the year after. Obviously always cut off any dead or broken branches and also any that look like they are going to touch the ground and also any very spindly growth should be removed at ground level.

Water blueberry plants generously immediately after they are set in the ground. Continue to water the plants so the interface layer at the bottom of the mulch layer remains damp. Monitor this 2-3 times per week in the first couple of weeks to build up a picture of how often the watering will be required as this will depend completely on the location and soil. Commercially on a sandy soil with modern automatic fertigation equipment, plants might be watered up to 7 times a day in the summer with a small amount of feed with all applications. If the soil is heavier then once per day in the summer is the norm. In a non commercial or manual environment this is unlikely to be achievable so compromises must be made. Certainly watering less than weekly in the summer will affect the plants

Fertiliser

Little and often is the preferred approach and if a fertigation system is not in place then use slow release fertilisers where possible. The types and amounts of fertilisers to use are far too big a subject for this quick guide, and you have no time to research this further yourselves, then a monthly application rhododendron fertilizer will do the trick. Take care that any granular fertiliser applied does not touch the stem of the plant. Blueberry roots generally grow out in an area of around 70-80cm from the stem, and the best fibrous roots will be only a few cm under the surface, and if you have followed the above instructions then these roots will be thickest along the interface layer between the underside of the mulch and the top of the soil. After say one year in the ground, a measure of a healthy plant is that you should be able to grab handfuls of this root 5-8cm under the surface about 30-40cm away from the plant and these roots should look fibrous and white in a solid matt as the plants get older.

General Management

Mulching

Apply a 5-7cm layer of pine bark or organic matter around the blueberry plants in early spring every year. Keep this mulch topped up as required in order to maintain a nice damp layer at the root interface layer and also to keep weeds suppressed. Do not allow weeds to grow within 60-90cm of the plant stem as they will compete with the plant for nutrients and the larger you allow them to grow, could disrupt the plant root system when pulled out and it is also good to keep air moving round the plant, especially at bloom – fruiting time to minimise the risk of botrytis (mould).

Pruning

Again a subject in its own right and this alone code take up a small book, but the most important thing is to know to prune EVERY year and the time to prune is any time during the winter once the plants are dormant. There are some lower chill types that are grown in warmer climates that you may read about as being pruned in the summer (these are known as Southern HighBush types – often abbreviated to SHB), but disregard anything you see like this as the plants that grow in the UK are Northern HighBush (NHB) varieties such as ‘Bluecrop’ and these require winter pruning.

Pests and Diseases

This quick introduction will not deal with this in any detail so research this on the web. Blueberries however are remarkably resilient to many of the common problems that are associated with other soft fruits, but they do come with a list of their own things to contend with! Commercially Blueberries are treated for pests probably less than any other fruit and so you are unlikely to have any issues with pests. Look out for aphis in the spring and treat in the normal way if they become an issue, you do not need to worry about the odd one or two as you should not need to worry about them being a vector of viruses in the UK. Blueberry specific pests include thrips which are becoming one of the most serious commercial pests commercially, and leaf midge (although this is usually only minor damage) and although many pests inflict minor damage this is usually not worth treating. As a general point, if the plant does not look well or just simply refuses to grow, the roots are the first place to look to see if they are healthy. Look for over watering or under watering signs, signs of roots being eaten by Chaffer grubs or

Birds can be a localized issue, in which case the only solution is to cover the plants in netting. If you do this, then use a wide mesh net so that air can freely flow through the plant and also there is no build up in humidity. Cover from first blue fruit and remove when you have harvested all that you want. Do not make obvious mistakes and cover with a finer net at flowering stage as otherwise the pollination will not be great!

Conclusion

You may be frustrated to know that Blueberry plants grow like weeds if in the right environment, but paradoxically they are however extremely fussy about where they grow – a lot more so than other soft fruit plants. Your plant is probably going to do very well or look like it’s trying to emulate a poor looking bonzi plant – rarely in-between! The UK climate is not the best for Blueberries but don’t let this put you off, just be aware of the extra care you will need to give – an analogy is that Grapes grow well in the South of France but are increasingly grown in the UK as the weather seems to be progressively getting warmer. Blueberries, like grapes, need a nice long period of warm weather to maximize the flavour of the berries, so don’t be afraid to let the berries hang for a while after they turn blue. If you find you need to pick them the nanosecond they go blue to get there before the birds, then make the effort to cover with some netting as a shame to get so close to the perfect berry. Lastly your plant will last as long as you want to keep it - there are commercial fields that are well over 30 years old in Poland and still going well. A typical NHB plant will take 6 years in the UK to get to full cropping potential, with first fruit in the 2nd year so be patient and concentrate on getting the vegetative growth in the early years.

Good luck with your growing, there is a wealth of information on the net about how to grow Blueberries, but if you follow the basics of the guidance above, you will be well on the way to having some of your very own superfood to eat. If your first few plants do well, the blueberries freeze extremely well and lose very little of their goodness when frozen, so don’t be afraid to plant some more and any surplus will be a welcome healthy addition to the freezer. Only buy from reputable sources as often varieties that growers do not want any more end up in garden nurseries. This is not always bad as can mean a good deal on some genuinely surplus plants but be careful. If the seller does not know the variety then not a good sign! If they do tell you a variety name then make sure they write it on the invoice as well, as plants all look very similar when young and less scrupulous sellers will strangely always have the variety that you are looking for!