- Horse Chestnut Seeds: How To Grow A Horse Chestnut Tree
- What are Horse Chestnuts?
- Growing a Horse Chestnut Tree
- Growing Horse Chestnut Seeds or Conkers
- Horse chestnut
- General use
- Side effects
- What’s the difference between horse chestnuts and sweet chestnuts?
- T.E.R:R.A.I.N – Taranaki Educational Resource: Research, Analysis and Information Network
- Life Cycle of a Conker
Horse Chestnut Seeds: How To Grow A Horse Chestnut Tree
For additional interest in the landscape, consider growing horse chestnuts. They’re perfect for adding drama either standing alone as a specimen planting or among other tree as a border planting.
What are Horse Chestnuts?
You may be wondering, What are horse chestnuts? Horse chestnuts (Aesculus hippocastanum) are large flowering trees, similar to buckeyes, with showy, white blooms in spring. These are followed by attractive, spiny, green seedpods from midsummer through fall. In addition to their beautiful flowers and seedpods, horse chestnut trees also exhibit interesting bark with twisted limbs.
One note of caution: do not confuse these ornamental tree with other chestnut trees (Castanea genus), which are edible. The fruit of horse chestnuts should not be eaten.
Growing a Horse Chestnut Tree
The most important factor when growing a horse chestnut tree is location. Horse chestnuts thrive in USDA plant hardiness zones 3-8 in areas having full sun and well-drained, but moist, humus-rich soil. These trees do not tolerate excessively dry conditions.
Horse chestnut trees are usually planted in spring or fall, depending on climate. Since they are normally purchased as container or burlapped plants, the planting hole should be about three times their width and deep enough to accommodate them with the top of the rootball flush with the soil.
Once the tree is placed in the hole, ensure it is straight before adding some of the soil to anchor it in place. Fill the hole with water, allowing it to absorb before adding organic matter and remaining soil. Tamp down lightly to eliminate any air pockets and add a layer of mulch to help retain moisture and keep out weeds.
Water newly planted trees regularly. Established trees require little care other than occasional pruning in late winter as needed.
Growing Horse Chestnut Seeds or Conkers
The horse chestnut can also be grown from seeds or conkers. The spiny seedpods drop from the tree in fall when ripened and crack open to reveal the horse chestnut seeds inside. Horse chestnut seeds should be planted as soon as possible. Do not allow them to dry out. They also germinate rather quickly and are best sown outdoors in a cold frame. They can also be placed in a plastic bag outside for a couple of weeks.
Once roots begin sprouting, plant them in pots of composted soil. Horse chestnut seedlings can be planted in their permanent locations the following spring or fall, or whenever they reach about a foot or so tall.
Growing a horse chestnut tree is easy and well worth the little effort involved. The tree makes a wonderful addition to the landscape for years of enjoyment.
The European horse chestnut, Aesculus hippocastanum, is the horse chestnut most frequently used in herbal medicine. It is a member of the Hippocastanaceae family. Horse chestnuts are in an entirely different botanical family from the well-known sweet chestnut tree, Castanea vesca. Horse chestnuts exist in nature as both a tree and a shrub, and are found in all temperate regions of Europe, Asia, and North America.
There are 15 recognized species of horse chestnut. The European horse chestnut is believed to have originated in the Balkan region of eastern Europe but is now grown in every country in the Northern Hemisphere.
The name Aesculus is actually a misnomer, coming originally from the word esca, meaning food. It was applied by ancient peoples to a certain species of oak; somehow the name was transferred over the years to the horse chestnut. The name hippocastanum is thought to refer to the horse chestnut’s ability to heal horses and cattle of respiratory illnesses. Another possibility may be that it is named for the small horseshoe-like markings that are present on the branches of the horse chestnut tree.
Horse chestnut trees grow in nearly any soil but seem to prefer a sandy loam. They grow very rapidly into tall straight trees that can reach heights of over 100 ft (approximately 30 m) tall, with widely spreading branches. The bark is grayish-green or grayish-brown in color, and the tree limbs are thick and have corky, elongated, wart-like eruptions that appear from a distance like ribbing. The interior of horse chestnut bark is pinkish-brown, with fine lines running its length. It is odorless and its taste is very bitter and astringent.
The characteristic horseshoe markings found on the branches are actually the scars from where leaves previously grew. Horse chestnut wood is seldom if ever used for lumber due to its soft and spongy character. Large leaf and flower buds are clearly visible even during winter months but are encased in a scaly, resinous protective covering that prevents damage from frost or damp. This thick sticky coating melts with the beginning of warm weather in spring, and flowers and leaves appear with remarkable rapidity, usually within three to four weeks.
The leaves are dark green, rough in texture, and large, with minutely serrated edges. Horse chestnut leaves can be nearly 1 ft (0.3 m) in length. They somewhat resemble a hand with five to nine leaf sections emerging from a palm-like base to form the finger-like projections. European horse chestnuts produce clusters of white flowers with a pale scarlet tinge at the throat or yellow mottling. American horse chestnut flowers can be white, pale pink, or yellow, depending upon the species. All types of horse chestnut trees, with their graceful wide limbs and showy flowers, are grown for their ornamental beauty.
The fruit of the horse chestnut is a dark brown smooth-surfaced nut approximately 2 in (5 cm) in diameter. It has a polished appearance except for the rounded dull tan-colored scar on the side that was attached to the seed vessel. Horse chestnuts are encased in a light green spine-covered coating that divides into three parts and drops away prior to the nut dropping from the tree. Horse chestnut nuts contain mostly carbohydrates which are generally indigestible until boiled. They also contain saponins, tannin, flavones, two glycosides, aesculin and fraxin, some crude protein, a fatty oil, ash and water.
Horse chestnuts native to North America are called buckeyes because of their large seeds which resembling the eye of a buck, or male deer.
American horse chestnuts are divided into four types:
- Ohio buckeye, or Aesculus glabra, is a medium-sized tree which grows from the southern United States to the prairies of western Canada. It is the state tree of Ohio, hence the state’s nickname of the Buckeye State.
- Yellow buckeye, Aesculus octandra, or Aesculus flava, is a tree which grows to heights of 40 ft (12 m) or more. It is fairly common across the central portion of the United States. Its leaves are somewhat smoother than those of other horse chestnuts.
- Red buckeye, or Aesculus pavia, is a shrub or small tree that generally is found in the southern United States. In early summer it develops brilliantly scarlet flowers in large clusters, and has dense foliage. The tree species of red buckeye grows to heights of between 15–20 ft (5–7 m) tall.
- California buckeye, or Aesculus californica, is a horse chestnut tree found all along the Pacific coast.
Horse chestnuts have been used as fodder for feeding farm animals, and some Native American peoples have included them in their diet. However, the outer covering of the horse chestnut nut is toxic, and the nut itself has to be boiled prior to being eaten safely. Its wood, which is too soft for furniture-making or construction, is used in building crates and other packing cases.
Both the bark and the fruit from horse chestnut trees are used medicinally to strengthen and tone the circulatory system, especially the venous system. It is used both internally and externally to treat varicose veins, phlebitis , and hemorrhoids. Horse chestnut preparations are particularly effective in treating varicose ulcers. Due to its ability to improve circulation, it is also helpful for the relief of leg cramps. Its bark also has narcotic and fever-reducing properties. A compound known as aescin, which is present in the horse chestnut fruit, is now often added to external creams and preparations used for the treatment of varicose veins , varicose ulcers, bruises, and sports injuries.
Horse chestnut preparations using the seed, bark, twigs, and leaves are all utilized in traditional Chinese medicine. Chinese herbalists consider horse chestnut to be a part of treatment not only for circulatory problems, but use it as an astringent, as a diuretic, for reduction of edema or swelling, to reduce inflammation, as an expectorant in respiratory problems, and to fight viruses.
Horse chestnut bark is removed in the spring in strips 4 or 5 in (10–13 cm) long, about 1 in (2.5 cm) thick and broad. The fruit of the horse chestnut is gathered in the autumn, when they fall from the tree. Both the bark and the fruit are dried in sunlight or with artificial heat, and are either kept whole or ground to a powder for storage. A decoction made of 1 or 2 tsp of the dried, pulverized bark or fruit left to simmer for 15 minutes in 1 cup of water can be either taken internally three times a day or used externally as a lotion. Horse chestnut preparations are also available as tinctures, extracts, capsules, and external ointments and lotions.
The outer husks of the horse chestnut fruit are poisonous. There are also reported cases of poisoning from eating raw horse chestnuts.
There have been reported cases of gastrointestinal irritation, nausea , and vomiting from taking large doses of horse chestnut. There are also rare reports of rash and itching , and even rarer cases of kidney problems.
Horse chestnut’s ability to reduce blood coagulation, or clotting, indicates that it should not be given to those with bleeding disorders or who are taking anticoagulant drugs. It is known to add to the action of such blood thinning drugs as warfarin or aspirin.
Grieve, M., and C.F. Leyel. A Modern Herbal: The Medical, Culinary, Cosmetic and Economic Properties, Cultivation and Folklore of Herbs, Grasses, Fungi, Shrubs and Trees With All of Their Modern Scientific Uses. NY: Barnes and Noble Publishing, 1992.
Hoffman, David, and Linda Quayle. The Complete Illustrated Herbal: A Safe and Practical Guide to Making and Using Herbal Remedies. NY: Barnes and Noble Publishing, 1999.
Taber, Clarence Wilbur. Taber’s Cyclopedic Medical Dictionary. Philadelphia: F. A. Davis Co., 1997.
Horse chestnut, any of several trees belonging to the genus Aesculus in the horse chestnut family (Hippocastanaceae), native to the North Temperate Zone. They have palmately compound leaves and erect flower clusters, often in the shape of an inverted cone. Prickly green husks ripen and split in fall to release one or two shiny mahogany-brown nuts. The tree’s common name is said to come from Turkey, where the nuts were fed to horses to cure broken wind.
Perhaps the best-known species is the common, or European, horse chestnut (A. hippocastanum), native to southeastern Europe but widely cultivated as a large shade and street tree; it grows to a height of 30 m (100 feet). The Champs-Élysées in Paris is lined with rows of horse-chestnut trees.
Japanese horse chestnut (A. turbinata) is as tall as the European species but is distinctive for its remarkably large leaves, up to 60 cm (2 feet) across. The Indian horse chestnut (A. indica), with slender, pointed leaflets, has attractive feathery flower spikes with a bottlebrush effect. Red horse chestnut (A. × carnea), a hybrid of A. hippocastanum and A. pavia, grows up to 20 m (65 feet) and has flesh-coloured to scarlet flower spikes.
What’s the difference between horse chestnuts and sweet chestnuts?
Chestnut is one of the world’s most popular and unique nut-bearing trees. Fresh chestnuts contain vitamin C and are much lower in fat than other nuts and contain twice as much starch as a potato, earning the chestnut tree the nickname “bread tree” in some regions of the world. Chestnut acreage in the U.S. has increased substantially over the past 30 years and Michigan boasts the largest number of growers and acreage in the United States. Michigan residents can benefit from our region’s agricultural diversity and often find Michigan chestnuts seasonally at local grocery stores, in roadside stands and at farmers markets.
Chestnut trees are found naturally in the landscape, in green spaces as ornamentals and are also planted in orchards for nut production. Edible chestnut species found in Michigan include the American chestnut, Chinese chestnut, Japanese chestnut, European chestnut and chinquapin. Consumers should be aware that the term “horse chestnut” is sometimes used to describe an unrelated tree in the genera Aesculus; trees in this genus may also be referred to as buckeyes. Trees in the genus Aesculus produce toxic, inedible nuts and have been planted as ornamentals throughout the U.S. and are sometimes incorrectly represented as an edible variety.
Left, edible chestnut with spiny husk and pointed tassel on tip. Center, fleshy husk of horse chestnut. Right, rounded toxic horse chestnuts without a tassel. Photos by Erin Lizotte (left) and Virginia Rinkel (center and right).
Edible chestnuts are easy to tell apart from unrelated toxic species like horse chestnut or buckeye. Edible chestnuts belong to the genus Castanea and are enclosed in sharp, spine-covered burs. The toxic, inedible horse chestnuts have a fleshy, bumpy husk with a wart-covered appearance. Both horse chestnut and edible chestnuts produce a brown nut, but edible chestnuts always have a tassel or point on the nut. The toxic horse chestnut is rounded and smooth with no point or tassel.
Quality, curing and season
The value of a chestnut is based primarily on its size and most nuts are sold fresh in the shell. Smaller quantities are available peeled and frozen or in value-added forms like chips, flour and slices. Chestnuts require a two- to three-week curing process to achieve maximum quality and sweetness. Chestnuts purchased from the store should have already undergone the curing process and should be ready to eat. Stores should be holding whole chestnuts under refrigeration for maximum quality. If you are purchasing chestnuts from a roadside market, be sure to ask if they have been cured. If you are collecting at a u-pick operation, it will be necessary for you to cure them yourself.
Peeled and frozen chestnuts. Photo by Erin Lizotte, MSU Extension.
During the curing process, starches in the nuts convert to sugar, making the chestnut taste sweeter. The best way to cure the chestnuts is to take time and store them just above freezing (32-40 degrees Fahrenheit) in your refrigerator for a couple of weeks. This longer, refrigerated curing process will increase their storability. The quickest way to cure chestnuts is to store them at room temperature for a few days; however, room temperature conditions will also dehydrate the chestnuts and so they will need to be consumed in a timely manner.
When selecting cured chestnuts at the store or market, consumers should inspect them carefully for quality just you would inspect a banana or pear. A ripe chestnut should have a slight give when squeezed, indicating they have been properly cured. A rock hard chestnut may require more curing time. A chestnut shell with a great deal of give indicates it is past its prime and has become dehydrated or has internal disorder. Lastly, when purchasing chestnuts, be sure the store or market is storing them in a chilled environment for maximum quality.
Chestnuts properly stored in a produce cooler at the grocery store. Photo by Erin Lizotte, MSU Extension.
When you get your chestnuts home, keep them cold but do not let them freeze (Due to their sugar content, chestnuts do not freeze until 28 F or below.). Store them in the produce compartment of your refrigerator where well-cured chestnuts can last for a few weeks. Ideally, place them in a plastic bag with holes made with a fork or knife to help regulate the moisture levels. If nuts are frozen, use them immediately after thawing.
The most recognizable and simple method of chestnut preparation is roasting. Chestnuts may be roasted in the oven, over a fire or even in the microwave. To roast chestnuts, be sure to score through the shell to ensure steam can escape and to prevent a messy and loud explosion. Scoring halfway around the equator works very well. Generally, it takes around 20 minutes in a 300 F oven.
For microwaving, the time can be as little as 2 minutes. Cook times can vary by microwave and oven, so some trial and error may be necessary and wrapping several nuts in a wet paper towel before microwaving works well. You can also try roasting them over an open fire or grill—though technically nestling them in the embers is best to prevent scorching. Depending on the temperature of the embers, this process can take anywhere from 15-30 minutes.
Cooked nuts should be tender, sweet and peel easily. Be sure to allow the chestnuts to cool before handling.
Remember, chestnuts aren’t just for roasting. Chefs around the world recognize their unique characteristics and produce delicious soups, pastas and spreads using this unique nut. Search online or in cookbooks to see how you can use this local food in your recipes!
For more information on Michigan produce, recipe ideas and preservation information, visit the Michigan Fresh page from Michigan State University Extension.
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Life Cycle of a Conker
by dontregartha October 10, 2017
Spend some quality time outside with your class and with nature to learn all about the great outdoors and the life cycle of a conker.
You will need…
- Shallow Gratnells tray with a 4-section tray insert.
- Horse chestnut tree bearing conkers
What to do…
- Head outside and find a big horse chestnut tree.
- Collect leaves, conkers in their casings, empty conker casings and ‘hatched out’ conkers.
- Place each item into a different section of the tray insert.
What is happening?
The horse chestnut is a deciduous tree. New leaves appear on the tree in early spring. In May the tree produces white and pink flowers. The flowers are pollinated by insects and each one develops into a conker (the seed) encased in a spiky green husk. In the autumn the husks split open, fall to the ground and the conkers fall out. Deer and other mammals like to eat the conkers, children also like to collect them and play the traditional game ‘conkers’ with them.
Further activities and questions?
Plant your conkers and grow new horse chestnut trees! Fill a deep gratnells tray half full with water and pop your conkers in. The ones that float can be discarded (or used for the other activities below), they have dried out and will not grow into new tree if planted. The conkers that sink can be planted individually about 2cm deep into posts of soil/compost. It is best to do this before the end of November. Water and place your pots in a sheltered spot outside. Protect the pots from predators and check regularly to see if they need watering. In the spring, re-pot young tress as they grow bigger. Once they are well established, plant your new trees out in a suitable spot – they will grow very large so think carefully about where to put them!
Play conkers: With the help of an adult, drill a small hole through the middle of your conkers. Thread ~30am string through the hole and tie a knot in the end so your conker cannot slip all the way through. Find a friend with a conker and challenge them to a match!
Conker creatures: Using conkers and other nature materials, make some minibeast inspired creatures or create your own mystical conker beast!
Health & Safety
As with all Gratnells Learning Rooms What’s in my tray activities you should carry out your own risk assessment prior to undertaking any of the activities with children.
I have been assured by a number of people that it is going to be a hard winter because the squirrels have been exceptionally active hoarding nuts. I want to believe this kind of observation because I want to tap into a knowledge that transcends and subverts the stultifying logic of measurement and science. I suppose the antithesis of this are the council goons that order chestnut trees to be cut down in case a conker falls on a passer-by or someone slips on a leaf.
A fully grown horse chestnut, Aesculus hippocastanum, will be more than 35m tall and almost as broad, and is unquestionably one of the finest flowering trees in the northern hemisphere. It is also one of those grown-up things that anybody in their right mind should celebrate, although conkers belong to children. I would love a conker to fall and hit me. Our own horse chestnut has not produced any fruit yet, but it is just six years old and they only start to flower around their seventh year. The flowers, balanced like pyramids of ice cream or white candyfloss, are at their best in early May, but the sticky buds break into glowing leaf in early April and the whole tree is a delight all spring and early summer. And in the hot, dog days of high summer, no tree casts such a congenial shade.
The conkers are the seed, with their pale hilum scar. The name comes from a dialectic word for snail shells, which were used for the game before the horse chestnut came on the public scene in the early 19th century. Before that they were the province of the private park, where all gathering of nuts, fruit or wild animals was considered poaching and punished with incredible harshness. So conker trees in public places represent a liberation of nature and public playfulness as well as decoration. It makes the action of the health and safety brigade doubly shameful.
Nothing has a sheen like a freshly exposed conker, and not many seeds are as beautiful as objects in themselves. I have just remembered that my twin sister and I used to make ‘beer’ by soaking handfuls of the empty seed shells or casings, which made a thoroughly satisfying froth and stained the water brown, which could then be poured into jugs. It had a sharp, slightly sour smell that was every bit as enticing as any proper beer has been to me since. In fact, the flower buds were occasionally used as a substitute for hops for making beer. In the second world war, conkers were roasted and ground to make a coffee substitute. By all accounts it was almost as disgusting as some of the insipid liquid that is often passed off as coffee by the various chains.
Horse chestnuts will grow fast and in just about any soil, reaching a great age. The oldest-dated trees in Britain are 400 years old now. They have been a completely friendly tree since they were introduced to this country in the early 17th century. They have no woodland or even rural association beyond a mannered parkland setting. Bushey Park has a superb avenue of them, planted by Christopher Wren in 1699, leading up to Hampton Court Palace. The Victorians loved them and you will often see them in parkland planted with similar huge exotics, such as with wellingtonias, copper beeches and London planes. For all their huge size, these are trees of domesticity. They are grown entirely for ornament, whereas almost all our native trees and quite a few introductions have had a range of essential uses throughout history. The timber of horse chestnut is soft and very white. It was apparently used for dairy maids’ buckets because, if kept wet, it is slow to rot. But the demand for dairy maids’ buckets has never warranted plantations of the trees even in the milkiest of times.
The red horse chestnut, A x carnea, is a cross with the red buckeye, A pavia, which is a very much smaller tree from North America, has rather dirty pink flowers which seem to me a pointless reduction of the incredibly beautiful white inflorescences of the original. It is smaller, rarely getting above 20m – which, I suspect, is why you quite often see it as a street tree.
A flava, or the yellow buckeye, has yellow flowers that open rather later and does best with some shelter until well established. There is also a cut-leaf job and a number of smaller trees, such as the sunrise chestnut (A x neglecta ‘Erythroblastos’) that read well on the page, but I confess I have never noticed them. The point is that the conker tree does it all.
The sweet chestnut, Castanea sativa, is a southern European tree and was almost certainly introduced by the Romans. It is happiest on well-drained or sandy acidic loams, so whereas the horse chestnut occurs everywhere, its sweet counterpart tends to be very localised. The casing of the nuts is as prickly as hedgehogs and they decorate the autumnal tree like limegreen Christmas baubles. The nuts are famously delicious but, unlike most nuts, they are relatively low in protein and fat but high in starch, so are traditionally used in chestnut-growing areas like the Pyrenees as a kind of flour to make bread and porridge. They need some warmth to mature, but perhaps one of the side benefits of climate change will be that we get a bigger and tastier chestnut harvest right across the UK.
The wood is fast-growing, hard and extremely long-lasting in the soil – ideal for fencing. The reason for this durability is that it forms a hardwood heart at a very early age and it is this that makes it able to cleave very cleanly and straight. I once bought 100 8ft chestnut stakes, each about 8in in diameter, and split them all into quadrants to use as the uprights for a woven hazel fence. Almost without exception this could be done cleanly using an axe and wedge. It was, slightly weirdly I confess, one of the most satisfying couple of hours of my life. Its ability to split into thin, strong posts make it ideal for paling or movable fencing that can be rolled up and quickly erected by the mile, yet remains almost as strong as oak. A thicker version of this chestnut paling was used in the Second World War to make over 1,500 miles of tank tracks on the Normandy beaches. Until 1900, all hops were grown up poles, each about 14ft tall and only about 1in in diameter at the tip. Each hop vine needed two poles, so around 2,000 were used for every acre of hops. This was serviced in Kent in particular (Herefordshire hops tended to grow up poles of coppiced ash) by coppices of sweet chestnut cut on a 10-year rotation. It is one of the best coppice trees, throwing up a mass of straight shoots with glossy saw-toothed leaves that have a remarkably exotic, almost tropical appearance.
This willingness to coppice can be used in the garden to make the tree into a multi-stemmed shrub, although if you have the space it makes a famously long-lived tree with close-ridged bark that often spirals around the trunk. The oldest surviving tree is reckoned to be between 3-4,000 years old and Sicily in particular has groves of very ancient trees. In this country there are numerous chestnuts that are medieval in origin although still callow in chestnut years, and if they are left to grow free from any council official fearful of branches falling on a litigious passerby, there is no reason to suppose they will not grow on for another thousand years yet.
Funnily enough a conker took my fancy on the way home a few weeks ago and I decided to grow it. Not having a garden outside at Loughborough, I decided to be awkward and do it the hard way: in pots. First thing I’ve done is pop the conker in some sllightly moist compost (reused as it happens) in a plastic tub with a lid and then stuck it in the fridge. Seems an odd things to do but the idea is to replicate the cold winter months – lots of seeds need such treatment to get them going.
When its been in there for a while I’m going to try a cheeky trick: I’m going to see if I can use tetrapaks to grow the seedling in (assuming it sprouts OK). I’ve got a stack of the blooming things and I’m determined to find a horticultural use for them! They should be a bit deeper than the average pot (especially if two are put together) so can handle a longer tap root from the conker. If it does take, I’ll then transplant it outside in the spring when the squiggles and other nut eaters won’t be so inclined to scoff it! Not quite sure where yet though.
When I was a kid I used the “chuck it in the ground in the garden, give it a water and watch it grow” technique. The tree grew to about 2m (took 5-6 years from what I remember) before it had to be removed as part of a garden redesign. The removal was “fun” – even a 2m horse chestnut has some serious roots and removing the trunk to beneath ground level just prompted it to put up a number of strong suckers in a couple of months. Digging all the roots out to stop this took ages. The moral of this story? Make sure that you plant the tree exactly where you want it to be for a long time! Away from buildings, drains, etc is a very good idea as well…
There’s also loads of acorns around this year so I’m also tempted to grow a few of those. I guess I should really wait until I’ve got some land to put a wood on first though!