A ha-ha is a feature used in landscape garden design to keep grazing livestock out of a garden while providing an uninterrupted view from within. The feature consists of a turfed ditch, one side of which is sloping and the other vertical and faced with stone or brick. Before the advent of mechanical lawnmowers a commonly used way to keep large areas of grassland trimmed was to allow livestock, usually sheep, to graze the grass. A ha-ha prevented the grazing animals on large estates from gaining access to the lawn and gardens adjoining the house, giving a continuous vista to create the illusion that the garden and landscape were one and undivided. The name "ha-ha" was given to the feature because, when walking towards it from the garden, it would only become apparent to the observer when close to it.
The basic design of sunken ditches is of ancient origin, being a feature of deer parks in England. The deer-leap or saltatorium consisted of a ditch with one steep side surmounted by a pale (fence) or hedge, which allowed deer to enter the park but not to leave. Since the time of the Norman conquest of England the right to construct a deer-leap was granted by the king, with reservations made as to the depth of the foss or ditch and the height of the pale or hedge. On Dartmoor the deer-leap was known as a "leapyeat".
The concept of the ha-ha is of French origin, with the term being attested in toponyms in New France from 1686 (as seen in modern times in Saint-Louis-du-Ha! Ha!), and being a feature of the gardens of the Château de Meudon, circa 1700. The technical innovation was presented in Dezallier d'Argenville's La theorie et la pratique du jardinage (1709), which was translated into English by the architect John James (1712):
"Grills of iron are very necessary ornaments in the lines of walks, to extend the view, and to show the country to advantage. At present we frequently make thoroughviews, called Ah, Ah, which are openings in the walls, without grills, to the very level of the walks, with a large and deep ditch at the foot of them, lined on both sides to sustain the earth, and prevent the getting over; which surprises the eye upon coming near it, and makes one laugh, Ha! Ha! from where it takes its name. This sort of opening is haha, on some occasions, to be preferred, for that it does not at all interrupt the prospect, as the bars of a grill do."
The etymology of the term is generally given as being an expression of surprise – "ha ha" or "ah! ah!" is exclaimed on encountering such a feature. This is the explanation given in French, where it is traditionally attributed to Louis, Grand Dauphin, on encountering such features at Meudon, by d'Argenville (trans. James), above, and by Walpole, who surmised that the name is derived from the response of ordinary folk on encountering them and that they were "... then deemed so astonishing, that the common people called them Ha! Has! to express their surprise at finding a sudden and unperceived check to their walk." Thomas Jefferson, describing the garden at Stowe after his visit in April 1786, also uses the term with exclamation marks: "The inclosure is entirely by ha! ha!"
In Britain, the ha-ha is a feature of the landscape gardens laid out by Charles Bridgeman and William Kent and was an essential component of the "swept" views of Capability Brown. Horace Walpole credits Bridgeman with the invention of the ha-ha (Walpole 1780), but was unaware of the earlier French origins.
"The contiguous ground of the park without the sunk fence was to be harmonized with the lawn within; and the garden in its turn was to be set free from its prim regularity, that it might assort with the wilder country without."
Ice houses are sometimes found built into ha-ha walls because they provide a very subtle entrance way that allows the ice house as a structure to be less intrusive. The ground also provides additional insulation for the ice house.
Most typically, ha-has are still found in the grounds of grand country houses and estates and act as a means of keeping the cattle and sheep out of the formal gardens, without the need for obtrusive fencing. They vary in depth from about 2 feet (0.6 m) (Horton House) to 9 feet (2.7 m) (Petworth).
An unusually long example is the ha-ha separating the Royal Artillery Barrack Field from Woolwich Common in southeast London. This deep ha-ha was installed around 1774 to prevent sheep and cattle, grazing at a stopover on Woolwich Common on their journey to the London meat markets, from wandering onto the Royal Artillery gunnery range. A rare feature of this east-west ha-ha is that the normally hidden brick wall emerges above ground for its final 70 or so meters as the land falls away to the west, revealing a fine batter to the brickwork face of the so exposed wall - this final west section of the ha-ha forms the boundary of the Gatehouse by James Wyatt RA. The Royal Artillery ha-ha is maintained in a good state of preservation by the Ministry of Defence, it is a Listed Building, and is accompanied by Ha-Ha Road that runs alongside its full length. There is a shorter ha-ha in the grounds of the nearby Jacobean, Charlton House.
In Australia ha-has were also used at Victorian-Era lunatic asylums such as Yarra Bend Asylum, Beechworth Asylum and Kew Lunatic Asylum. From the inside, the walls presented a tall face to patients, preventing them from escaping, while from outside they looked low so as not to suggest imprisonment. Kew Asylum has been redeveloped as apartments; however some of the ha-has remain, albeit partially filled in.
Ha-has were also used in North America. Only two are believed to remain in Canada, one of which is on the grounds of Nova Scotia's Uniacke House (1813), a rural estate built by Richard John Uniacke, an Irish-born Attorney-General of Nova Scotia.
A recent use of a ha-ha is at the Washington Monument to minimize the visual impact of security measures. After 9-11 and another unrelated terror threat at the monument, authorities had put up jersey barriers to restrict cars from approaching the monument. The new one-sided ha-ha, a low 0.76 m (30-inch) granite stone wall that doubles as a seating bench and also incorporates lighting, received the 2005 Park/Landscape Award of Merit.
In fiction 
- In the Terry Pratchett Discworld novel Men at Arms, a similar landscape boundary is used for a comedic twist: designed by ill-famed engineer Bergholt Stuttley Johnson, the ha-ha is accidentally specified to be 50 feet deep, is called a hoho, and is reported to have claimed the lives of three gardeners. In Pratchett's book with Neil Gaiman, Good Omens during a gun battle at an old English country house a character in the book is said to be lying face down in the ha-ha, but not to be very amused by it. In Snuff, as Vimes and Willikins go for walk in the countryside, they "navigate their way around the ha-ha, keep their distance from the ho-ho and completely ignore the he-he."
- In The Island of Doctor Moreau by H. G. Wells, a "steep-walled gap" on the island is compared to "the ha-ha of an English park"
- Edward Gorey's The Awdrey-Gore Legacy, a satire on overcomplicated murder mysteries, ha-ha is one of the typical places where the body of a murder victim might be found
- In Tom Stoppard's Arcadia, the ha-ha is discussed in relation to the Capability Brown garden and is used as one of the links between the nineteenth and twentieth century characters
- In Jane Austen's Mansfield Park a ha-ha prevents the more sensible characters from getting around a locked gate and into the woodland beyond.
- In Diana Wynne Jones' sixth Chrestomanci novel Conrad's Fate, Christopher and Conrad both stumble upon a ha-ha while exploring the mansion grounds. Christopher declares the ditch to actually be a ha-ha, and Conrad mistakenly thinks that he is laughing.
- In Ford Madox Ford's novel The Last Post, Mark Tietjens, pondering the proposed removal of Groby Great Tree to please a prospective lessee of the Groby estate, considers that the decision to plant a grouping of trees used to be discussed with the heirs who would see them mature and imagines how the placement of copper beeches against a "haha" a quarter of a mile from the ballroom windows might look in thirty years time.
See also 
|Look up haha in Wiktionary, the free dictionary.|
|Wikimedia Commons has media related to: Ha-has|
- West Dean College: "From the front the parkland landscape appears continuous, but in fact the formal grounds are protected from the grazing sheep and cattle by a ha-ha"
- "Lawn Pros and Cons". Pat Welsh. Retrieved 2013-04-15.
- Massachusetts Agriculture: "Early suburbanites relied on hired help to scythe the grass or sheep to graze the lawn. The lawn mower ... made it possible for homeowners to maintain their own lawn. ... The ha-ha provided an invisible barrier ... which kept livestock from wandering ... into gardens. "
- The first European attempt at a concerted account of Chinese gardening is Sir William Chambers, A Dissertation on Oriental Gardening, London 1772.
- Shirley, Evelyn Philip (1867). "1 Deer and deer parks". Some account of English deer parks: with notes on the management of deer. London: John Murray. p. 14. Retrieved 2012-11-24.
- Anon. "Okehampton Deer Park". Legendary Dartmoor. Retrieved 24 November 2012.
- The Papers of Thomas Jefferson Digital Edition, ed. Barbara B. Oberg and J. Jefferson Looney. Charlottesville: University of Virginia Press, Rotunda, 2008, p. 371. Online edition accessed 14 Aug 2012.
- Horace Walpole, Essay upon modern gardening, 1780
- Hamlin, Ann (1987). Iona: a view from Ireland. Proc Soc Antiq Scot, ISSN 0081-1564, V. 117, P. 17
- Walker, Bruce (1978). Keeping it cool. Scottish Vernacular buildings Working Group. Edinburgh & Dundee. Pages 564-565
- Large Associates website[dead link]
- Kew Lunatic Asylum - Historic Walk Australian Science Archives Project, [Kew Lunatic Asylum]
- Washington Monument (from the OLIN website)
- Monumental Security (from the American Society of Landscape Architects website, April 10, 2006)
- Annotations from Terry Pratchett's Men at Arms (from The Annotated Pratchett File v9.0
- Terry Pratchett - Snuff (2011) page 56. (Corgi Books ISBN 978-0-552-11675-1)