In a chestnut
Knowledge is key when it comes to deciding which type of chestnut you want to grow in the garden.
Was there ever a common name that could both excite and disappoint as much as ‘chestnut’? It describes a variety of tricksy trees, the edible version having a green hedgehog wrapped around its (often small) nuts, and the non-edible one having large, easy-to-pick-up, luscious-looking nuts – oh, and it is annoyingly prolific. So what’s going on and why can’t we eat both? The answer is because, while they share the chestnut name, they come from two different genera and therefore have quite different attributes and characteristics. You will find the edible version is Castanea and the nonedible, also called horse chestnuts, is Aesculus.
CASTANEA
The chestnut up first has a long history. It has been cultivated as a food crop for more than 3000 years, including being taken to England by the invading Romans.
Castanea sativa, the sweet or Spanish chestnut, is a large tree, with the ability to grow up to 15–30m given (a lot of) time, so choose your placement with this in mind – you may not get to see it at this size, but future generations will. The leaves have serrated edges and a shininess to them that is attractive, and the flowers appear as long creamy catkins (usually both male and female) in midsummer, then develop into prickly cases surrounding the nuts, often three nestled together. For a good crop of nuts, cross-pollination is required. For a self-fertile chestnut, plant C. sativa ‘1005’. Reaching ‘just’ 10m, it has the additional advantage of producing one decent-sized chestnut instead of three smaller ones. Plus, you don’t have to wrest the nut from the prickly case as they easily fall out.
There is another edible chestnut, a variegated variety called C. sativa ‘Albomarginata’ that used to be available in New Zealand. I don’t know if it still is, but I am hoping that it is still around and that someone, somewhere, is propagating it. Look out for it as it is a handsome beast – the leaves have creamy-white edges and the spines on the burrs are white also.
EATING CHESTNUTS
I have memories of being in my happy place in front of my nana’s open fire, roasting chestnuts, splitting them open when they were done, then adding butter, salt and pepper – just yum. The taste is hard to describe, sort of like a dry kūmara. They can also be boiled, baked, cooked in a fry pan or microwaved. Make a little hole in the nut to avoid any explosions. While some recommend you soak them before roasting, I haven’t noticed any advantages in doing so.
CULTIVATING CASTANEA
Castanea trees are hardy, coping with drought once established. They enjoy slightly acidic, freedraining soil and cope with frost, wind and so on.
AESCULUS
The horse chestnut is another substantial tree growing to 15m, and the one that you see planted as a street or park tree. When in full-on flower, these trees stop you in your tracks; it just doesn’t get any lovelier.
Aesculus hippocastanum, the common horse chestnut, is the ‘conker’ tree that is used in those fierce English conker games. The nuts (two of them) are contained in cases that look a little like armour or the maces that used to be used to crack heads. Big, bold, 30cm conical white flowers, with a touch or red and yellow, appear in spring among the fan-shaped leaves.
A shorter version is A. hippocastanum
‘Baumannii’. It grows to 8m, and this time the white flowers are double and, pleasingly, it stays in flower for longer than A. hippocastanum.
Another white-flowerer is the Indian horse chestnut, A. indica. The panicles of frilly, daintylooking flowers that appear in early summer are flushed with pink – and 36cm long! The leaves merit a mention – they start off bronze in spring and turn dark green, finishing with an orangeyellow flourish in autumn. This is another biggy, growing to 15m in height.
If you fancy pink flowers instead of the white, choose A. × carnea, the pink horse chestnut. Producing large 20cm-long rose-pink coneshaped flowers with yellow blotches, it grows to a more diminutive height of 7m.
For red flowers, there’s A. × carnea ‘Briotii’. A compact grower to 6m, the sizeable red flowers appear in late spring and the colour pops against the green of the leaves. This variety does not produce nuts.
You may have heard the term ‘buckeye’ in relation to chestnuts. A. pavia, the dwarf red buckeye, and A. flava, the yellow buckeye, are both American in origin. They differ in height and flower colour, with A. pavia growing to 4–5m tall and producing red flowers, whereas A. flava grows to 12m or more and has yellow flowers.
There are some less well-known Aesculus varieties worth a hunt. A. × neglecta ‘Erythroblastos’, the yellow (or Carolina) horse chestnut, produces shrimp-pink leaves in spring, turning a pale yellowy-green as they age and is modest in height at 5m – keep it out of the wind to preserve the foliage. Another is A. turbinata, the Japanese horse chestnut, which needs space to grow, reaching up to 15m, with white flowers in late spring. The fan-shaped leaves are oversized, and the nuts are a little different to the others, being not just smooth instead of bumpy, but also pear-shaped.
GROWING HORSE CHESTNUTS
Horse chestnuts like moist soil, fertile if possible, and they prefer to be out of strong winds – though I have seen them coping with the strong nor’west winds down in Canterbury.
ANYMORE TO KNOW?
It’s probably wise to mention that horse chestnuts are unfortunately toxic (the poison aesculin is present) to horses, and humans. About the only animals that can tolerate them are deer and pigs.
Chestnuts – both edible and non-edible – are great trees to plant if you have the space to let them grow up and out. Plant one for the chestnuts and the other for the flowers and you will have the best of both worlds.