The Common Horse Chestnut, Aesculus hippocastanum

https://theecologist.org/2017/may/12/demise-horse-chestnut-tree-armageddon-or-scaremongering

https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.13116

The Japanese Horse Chestnut, Aesculus turbinata, not.

Owen Johnston has identified a tree in the Horse Chestnut collection at the front of Hadlow College as the Japanese Horse Chestnut, Aesculus turbinata.. I think that this species is really very similar to the common Horse Chestnut, A.esculus hippocastanum., but the tree identified is fairly certainly the Yellow Buckeye, Aesculus flava.

The pear-shaped(really?) fruit of pure Aesculus turbinata is without spines, although they may be warty and the hilum on the conker is much bigger than Aesculus hippocastanum, making the species easy to distinguish when with ripe fruit. There is a full range of hybrid types!

The leaves of Aesculus turbinata are a little more regularly toothed, narrower, to 40 cm, not so obviously wide above the center, and tapering more gradually to the tip. The leaflets do not have a petiolule, unlike the Indian Horse Chestnut, Aesculus indica. The underside of the leaves should be glaucous green, with hairy veins, rather than yellow green. The autumn colour is supposed to be "distinctive" - reddish perhaps. The buds are viscid. 

The flower spikes or panicles are bigger (25 cm x 6 cm) but supposedly rather less obvious, a little more "hidden" than those of Aesculus hippocastanum, and produced about 2 - 3 weeks later. The petals should be cream with red spots. 

There are two trees there at the moment, one bigger, one smaller, both in early stages of leafing out - could one of them, or both, be it?? Neither tree matches Aesculus turbinata. My best guess is that the biggest tree is Aesculus flava, and the smaller is Aesculus indica.

The interesting tree at Luddenham Court, visited in the second half of April, next to the Red Horse Chestnut, Aesculus x carnea, is quite a possibility. The leaves are already quite tattered, a bit like a Common Horse Chestnut, which I haven't seen in the on-line pictures much. however the key feature I was looking at was the absence of spines on the first stage of the developing fruit, so I was pretty sure it was not Aesculus hippocastanum.  The leaflets did not have red petiolules, so it could not be Aesculus indica, the other major possibility.  However the flowers were very white rather then cream, rather pretty and bright, and the leaves did not look that much different from Aesculus hippocastanum. Also, I didn't note any obvious glaucous underside of the leaves. 

The Red Horsechestnut, Aesculus x carnea, including 'Briottii'

The "Red" Horse Chestnut is a (tetraploid?) cross between the shrubby Red Buckeye or Firecracker, Aesculus pavia of the mid-west USA and the Common Horse Chestnut, Aesculus hippocastanum, of South Eastern Europe. The hybrid appears to have been around since early Victorian times, possibly arising in Germany by 1820.


It is a generally "desired" tree although Alan Mitchell, writing in the 1970s,  disparages it greatly, as dark and uninteresting, but thankfully short-lived! Does not get much Horse Chestnut Leaf Miner, which is a relief. A bit less troubled by diseases than A. hippocastanum, but does seem to have physiological bark breakdown problems and to get bleeding canker a lot, limiting its life span.

There are three red horse chestnut trees at the front of Hadlow college, one by the road and two by the river. They vary slightly in the hue or "redness" of the flowers, but whether one or more is actually "Briotii" is a guess well above my pay grade - but I think NOT. 

Could this one be 'Briotii'?

According to the RHS Dictionary, the tree is "low-domed" but this must be relative. The bark is said to turn from dull green tinged pink, becoming red-brown and rough with distinct lenticels. The branches are said to be twisted and spreading, with drooping tips.

 The buds are terminal, often in pairs. They are up to 2.5 cm long, ovoid and slightly resinous.

There are 5 - 7 leaflets per leaf, each sub-sessile, obovate up to 25 cm long, actually broader than in A. hippocastanum (?), wrinkled, dark green above, lighter green beneath, double crenate, the leaf with a petiole of maybe 23 cm. The leaves should often be recurved and twisted. Midrib is red at its origin?

The flowers form panicles 20 x 10 cm. The flower corolla is up to 1 cm in length, the petals rose-pink, their centres blotched yellow initially, then the centre turning cerise as the flower is pollinated. The petal margins should be glandular - which I have never noticed before! Stamens protrude slightly, but nothing like as far as in A. hippocastanum.

The spiny fruit is spherical and up to 4 cm diameter. There are 1 - 3 small seeds or "conkers".

'Aureo-marginata' Leaves edged with yellow.

'Briotii', perhaps called the Ruby Horse Chestnut, has a larger inflorescence, with much darker red petals, with a glabrous pistil. The fruit is only laxly spined. Notably dark green foliage. Red "midrib" - (must be petiole)? The cultivar was named in 1858 to honor Pierre Louis Briot (1804-1888), the chief horticulturist of the State gardens at Trianon-Versailles near Paris,

'Foliis Marginatis'

A variegated form with a dark green border to the leaf, then an irregular band of yellow, the centre being pale green

'Fort McNair' (named from where it was selected) has dark pink flowers with yellow throats and resists leaf scorch and leaf blotch. It has a more 'pavia' type leaf.

'O'Neil', or 'O'Neill Red' produces larger (10–12 inch) panicles with brighter red flowers. Introduced by Monrovia nursery in about 1979 (Jacobson,1996).  Monrovia spells the cultivar name as O'Neill; many variations of this name are found in nursery catalogs and horticultural publications.

'Plantierensis' is a back-cross to A. hippocastanum. There are usually 7 sessile leaflets, uneven with ribbed blades. The inflorescence is very like A. hippocastanum but a delicate pale pink. The fruit is prickly but undeveloped, as it is triploid, so you don't get conkers. The origin of this cultivar is the nursery of Simon-Louis Frères, Metz, France, 1894.

'Theo Jansen'.

See list at Pavia Nurseries, Holland, a leading supplier of Aesculus plants in western Europe.

There are some very nice Aesculus at the Almshouses, Faversham, including this very pretty Aesculus x carnea.

The Ohio Buckeye, Aesculus glabra

Fascinated by this tree just by the Guild Hall in Faversham, the County Champion for girth and height.

Description: 10 - 30 m. tree, bole to 40 cm diameter. Bark light to dark grey-brown, becoming much lighter, fissured. Red-brown branchlets becoming light-grey. Buds conical, acute. Leaflets 5 - 7, 6 - 16 cm long, 2 - 6 cm wide, obovate to elliptic, long acuminate, acute at base, glabrous to tomentose beneath, dark green, toothed towards apex, petioles 5 - 15 cm. The leaves are said to smell "off" when crushed, hence the foetid buckeye. Good autumn colour.

Peduncles and pedicels are hairy. Flowers in 10 - 15 cm, glabrous to densely hairy, calyx cup shaped to 1 cm, lobes obtuse. 4 pale yellow green fringed petals form the corolla, up to 2 cm long. Upper one with  a hairy claw to half its length, lateral ones have a shorter hairy claw and are broader and ovate. 7 long stamens exserted to 2.5 cm, with orange anthers. Light brown ovoid fruit up to 5 cm diameter, more or less prickly, contain 1 - 3 dark brown conkers 2 - 4 cm diameter.

https://www.minnesotawildflowers.info/tree/ohio-buckeye

The flowers are probably quite pretty in close-up:

The Buckeye is a very nice tree and the state tree of Ohio, the Buckeye State. People used to carry the nuts in their pockets against rheumatism. All parts of the tree are potentially toxic however. People of the First Nations used to extract tannic acids from the nuts to tan leather and are also said to have used powdered nuts in water to stun the fish. Turned out quite symbolic in the election of President William Henry Harrison, who was from Ohio.