Plant Profile- Blueberry

Some plants are more generalists that can potentially grow in a pretty wide range of conditions, while others are specialists that are only viable or competitive with other plants in a pretty narrow range of conditions. The plants we have domesticated are generally at the generalist end of the spectrum since we prefer to plonk them down where we want them to grow like pieces of cheap furniture and expect them to tolerate our clumsy abuse. Weeds are usually fairly generalist plants that take advantage of the disturbance we create wherever we go. By contrast specialist wild species are a huge challenge to cultivate, requiring the right combination of soil structure and chemistry, local topology, temperature, rainfall patterns and soil microbiology along with other crucial factors. Get one factor wrong and they simply refuse to grow.

Blueberries are pretty unusual for domesticated species in being fairly specialist in their requirements, though they were only domesticated quite recently. The modern farmed types trace their parentage back to wild species that grow in regions just a bit higher than swamps, with nutrient poor acidic soils with a fairly constant level of moisture, growing widely in the USA. The more northern species Vaccinium corymbosum was domesticated as the northern highbush blueberry, and was hybridised with Vaccinium darrowii to make the more subtropical southern highbush blueberry, along with a couple of other species. Various species of blueberries are found across Asia and as far south as Costa Rica, Hawaii, Madagascar and South Africa. The wider Vaccinium genus includes other fruiting species like cranberries that grow in even wetter conditions.

My own experiences with blueberries got off to a pretty rocky start that was ultimately informative. Their fine, fibrous root system means that transplantation is always slow and difficult, and their very particular soil requirements mean it took a lot of trial and error to find places where they could grow well. My oldest and largest plant is growing on the edge of a dam in a fairly dry looking spot, but I strongly suspect ground water accumulates coming down the hillside in this location since it stays green for longer than other places during droughts. Our soil is a cracking clay for the most part with a pH around 5.1. Blueberries are more competitive around 4.5, so lower spots that tend to accumulate acidic leaf litter are best, though they need to be well drained and not prone to becoming boggy.

This inspired me to trial planting some in an odd location on the bank of our creek. The area is hollowed out from the bank like a natural amphitheatre and the soil on the lower part remains boggy even during prolonged droughts, while a little further up is almost never muddy, meaning ground water is close to the surface in between. This ground water is apparently coming down the hill above, which acts as a massive water tank for the amphitheatre. To improve the acidity and leaf litter I planted casuarinas in a ring around the highest and driest part of the amphitheatre, which should also provide a little light shade. A test planting of a half dozen small plants that were ignored once planted yielded two successfully established, not a great rate but fairly typical for store bought plants. We did go into a hot and dry spell immediately after transplanting as well, but the location is a long way from the house and I had other things to worry about.

Killing expensive store bought plants gets old after a while, so I decided to propagate my own. Cuttings were very hit and miss (apparently benefitting from misters on automatic timers and plenty of rooting hormones….too much bother for me). Seed seemed like a better way to generate a large number of vigorous and diverse plants to establish larger plantings- I could easily use a few dozen bushes. Fruit were collected from a few different bushes and mashed in water by hand. This year I am doing the processing in a blender since the seed are so tiny they aren’t damaged. The pulp is sieved so the seeds can pass through, though I often water down the unsieved pulp to save a few larger seeds. The seeds sink to the bottom so the skin fragments and pulp can be decanted off. With a few repeated washings clean seed can be produced. This seed needs a period of chilling to germinate, so I put it in a zip-lock bag of damp peat moss in the fridge over summer. After a few months a few white sprouted seeds should be visible. I then tip out the peat moss into a pot to sow, with extra peat mixed into the seed raising mix. They love being damp so sitting in a shallow tray of water works well. I tried germinating seed from commercial frozen berries and some fresh berries from the shops as well and had some come up, while the home grown seed germinated strongly. Seedlings were transplanted into individual small pots when they were 1-2 cm tall and grown on. Their vigour is very encouraging with the largest already over 20 cm tall after about nine months from germination, and they will be planted out in the amphitheatre and a damp gully in my orchard once the summer rains start up. I’m hopeful these smaller plants will establish more readily since their root systems aren’t as congested as the larger cutting grown plants you usually find in nurseries.

This genus holds a lot of promise in my eyes. They produce at a very useful time of year around December, when not much else is producing. The fruit don’t seem to be that interesting to our local birds either, with decent harvests without netting. This might change as I plant more of them if the birds change their minds. The biggest potential however lies in the huge genus of related species. The highbush blueberries went from locally adapted wild species to commercially viable strains within a single person’s lifespan. I hope I can reproduce this feat with other species on my farm. With Vaccinium my plan is to track down some of the more subtropical species and try a bit of hybridising for myself, but first I will need to establish decent stands of locally adapted commercial types. This remarkable genus also reminds me of the advantage of growing the right plant in the right place. Rather than choosing where I want to grow blueberries then forcing the soil to be damp, acid and peaty by using loads of inputs I have the option of exploring the wider landscape to find the locations that are already suitable. Zero input agriculture means accepting that you can’t grow every plant in every location.

My largest and oldest bush on the dam edge. Fruit are netted to prevent birds taking them but unnetted fruit are ripening nicely anyway.

My largest bush in the amphitheatre.

A wider shot of the amphitheatre. This was once 6 feet deep in Setaria grass, a few stragglers of which were recently sprayed. Bamboo and Casuarina line the steep banks.

Cleaned blueberry seed ready for chilling in the fridge.

Last years blueberry seedlings waiting for rain before transplanting.

A small handful of fruit in front of my muddy dam. That large bush is producing well despite this being one of the driest springs on record and receiving zero irrigation since planting.