One major influence on my approach to growing has been Mark Shepard. This pioneer of agroforestry moved to a part of the USA that everyone thought was too cold for chestnuts and proceeded to develop his own highly successful and productive forest system. His strategy was pretty simple- plant as much diversity as he could get his hands on and then let the plants themselves decide if they wanted to grow and produce or not. Every time a tree died Mark said thank you as it was weeding itself out of the gene pool. He now has his own locally adapted strain of chestnuts (among many other species) that produces well far outside the previously accepted range. When I reached out to Mark at the start of developing my farm his excellent advice was to start with the most locally adapted species, including our criminally underappreciated bunya nuts. I decided to at least dabble with chestnuts as well to see if I could develop them in the other direction to adapt to a hot and humid climate.
Chestnuts have some considerable advantages over other trees. The nuts they produce are rich in starch (unlike most other oily nuts), making them a useful staple crop. Ancient societies frequently relied on chestnuts for a substantial part of their diet, especially during years when their grain crops failed. The nuts form in spiny burrs that are quite effective at deterring parrots. The trees are also relatively fast growing and can mature quite quickly as well. Experimental breeding work in the early 20th century by the incomparable self-taught plant breeder, Luther Burbank, revealed it was possible for trees to start flowering six months from seed. This sounds incredibly exciting, but following up on this work it turns out those ultra-precocious forms put so much energy into nut production they struggle to grow into a reasonable sized tree after many years. Like most things in biology there are trade-offs between different functions so there is no free lunch. Chestnuts can produce 500-1000 kg of nuts per acre, comparable to industrial corn at 3500 kg per acre, but chestnuts do it without the annual ploughing and erosion and can be intercropped with other plants.
My initial experiments with chestnuts started with grafted and seedling trees bought from an interstate specialty tree nursery. This nursery produces excellent quality trees and stock varieties that are otherwise impossible to find, so I am very grateful that they are in business and charging the prices necessary to be sustainable as a business. The trees were planted in a section of orchard that I noticed had especially friable soil since I had read that chestnuts dislike waterlogged soil. They were planted into the weedy former cow paddock, given tree guards and watered a half dozen times with dripper bottles (1.25 L PET drink bottles with two holes drilled in the lid, placed upside down in the tree guards). While the trees seemed to grow reasonably well to begin over time they petered out one by one, often years after planting. Whether the cause was too much water or drought I don’t really care since I wasn’t going to break my back trying to mitigate either. One graft has persisted to this date and luckily it has some precocious and productive traits that are noteworthy.
At the same time I hedged by bets and tried a few different approaches. A bundle of seedlings arrived from an ebay seller in Townsville, with no information on their origins. These sad little plants arrived bare rooted, wrapped in damp paper and with barely any roots. I didn’t hold much hope of them growing but planted them out into tree guards, watered once and forgot them. Around the same time I also tried sowing chestnuts from the shops, both in pots and direct in the ground. Germinating chestnuts in pots is tricky since the large seed seem to need abundant oxygen to sprout without rotting. Barely burying them under a layer of coarse mulch or a sheet of hessian seems to suit them. Those in the ground were also barely covered. Those in pots germinated reasonably well but only gave less than 50% transplant success, another plant that resents root disturbance. Those direct sowed germinated at a bit over 50 % and I was surprised the rats didn’t take them all. Plants derived from all these different methods are now well established about five years later, with the tallest ones reaching 4-5 m in height. This is despite them not being watered, weeded, fertilised, sprayed or pruned and being buried in grasses and weeds most of their lives.
The seed grown trees are now reaching maturity, producing sickly smelling catkins in spring as the leaves burst out of winter dormancy. With a dozen or so mature trees flowering their wind pollinated flowers are more likely to cross with a neighbour. Like a lot of trees chestnuts benefit from growing in colonies with diverse genetics to ensure good pollination. In previous years seed has mostly set on my single grafted clone, presumably from pollen off some of the seedlings since its seed set improved dramatically as they started to flower alongside it. These seed that are produced in autumn are germinated each year and planted out the following spring to fill in gaps in the chestnut grove. Every year, especially during our hot and wet summers, a tree or two drops dead. As long as enough remain to produce seed and start new generations I am not too worried. If they all die then I will probably end my chestnut experiment, satisfied I gave it a decent try. If not they will continue to settle into the farm and spread to any space that suits them.
9 thoughts on “Plant Profile- Chestnut”
You should check out varieties from Galicia, Spain,:Martaiña, Longal for example. It is a very humid climate that has been growing chestnuts for thousands of years, sometimes as a staple. Although the summers here are dry, our springs are wet, so the flowering here happens during rain, And we have chestnuts here growing alongside wetlands.
I would love to get wider genetic diversity of chestnut but we are very restricted in what we can bring into Australia. For that reason it is likely chestnut will always be a marginal crop for me here, though you never know what random crossing of what we have might turn into.
Don’t know if you’ll see this comment on an old post, but Mark is the one who layed out the swales here and planted chestnuts from his farm. As you say, the genetics are whatever has survived so far, but ( in general) his are a mix of Chinese (castanea mollissima) and American (castanea dentata) chestnut. Which leads to my question- Are yours primarily or wholly Chinese? If not, the blight might well be a factor also.
Anyway, my big problem was deer predation before I got the protection adequate. The best are still not nearly as large as yours. What is the dormancy period for them in your climate? Since we have long winters here, they lose a lot of growing time each year.
Australian chestnut genetics is mostly European but there might be some Chinese in the mix. We definitely are starved for choice in genetics compared to Eurasia and north America. Chestnut blight hasn’t officially made it to Australia (though there have been limited outbreaks in the cooler south where chestnut orchards are usually found). It is a bit sad since so much work is being done with blight resistant genetics overseas. If we converted to these superior forms then we wouldn’t need to worry about the high chance of blight eventually getting established here. As it is we are just waiting for disaster in established orchards when it finally gets out of control.
My trees drop their leaves around May and leaf up again in September, so a very short dormancy compared to colder climates. Some trees vary by a month or so either side since my genetics is whatever I could find. Our main herbivore here is kangaroos/wallabies, but they generally don’t come over to where the chestnuts are currently growing. As my stocks increase I will be planting seedlings out in the bigger kangaroo paddock and will see how they go. They generally don’t like tannin rich plants so hopefully the impact will be minimal. If newly transplanted trees are getting hit hard by deer it might be due to them being rich in trace elements from fertilisers while in the pot. I mostly lose trees during our hot/wet time of year when the weather is like northern Florida, though we often get very hot summer droughts that are similar to coastal Texas. Suddenly transitioning from hot/dry to hot/wet kills off a lot of established plants, but the chestnuts seem to mostly handle it here. I read the some of the American native chestnut species grow on magnesium rich clay, so maybe our weird soil is close enough to that to actually suit them.
Another comment on an old post – hope you see it. Have you tried air pruning beds for nut tree production from seed – like Edible Acres and Twisted Tree Farm? I tried it last year for the first time and it worked really well. It is apparently a gentle way of killing off the tap root and persuading the trees to switch to a fibrous root system which makes transplanting much more successful.
I do have a stock of root pruning pots but find them difficult to keep the medium in and keep moisture levels up. I will try them for some chestnuts, but they seem to prefer a mineral type native soil which might come out the holes too easily. Taproots are an advantage in my mind if you can get the seedling out quickly enough (or better yet direct sow).
I completely agree about root pruning pots but an air pruning bed is quite different and is very good at maintaining moisture levels if done properly. I agree tap roots are ideal but incredibly difficult to achieve if germinating big seeds like chestnuts (and most nuts) in a nursery situation. Direct seeding would be ideal – I must put some thought into how to protect the seeds in the ground before they germinate.
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Some of my plantings were done with this type of seedling. The tubeling worked well for the tap root type of tree like the chestnut. These were live late spring plantings, not bare root dormant. Timing is important. Your weather is different, so maybe not as tricky.
This business is defunct, but their website is still up. I imagine the tubes are available at nursery suppliers?
Of concern with chestnut planting even like this is that the nut will attract critters and end up damaging or killing the plant when going for the nut. wire cloth or other protection is needed.
My best chestnut trees were from direct seeding, though the success rate varies a lot in different years. Vertebrate pest pressure is surprisingly variable as populations shift and vary. Given the long time to maturity and long lifespan of trees I wonder if it ends up being more practical to do direct sowing, provided of course you have plenty of seed to “waste” during unsuccessful years. Even if you only get good germination once every five years direct sowing for five years versus potting, watering and then planting out (assuming that none of those steps go wrong either)…..my gut feeling is you would need to have less than one in ten successful direct sowing years for growing in pots to be less resource intensive. Natural forests often have this dynamic with effective seedling recruitment for trees only happening at widely spaced intervals in time when conditions are just right.