A ha-ha is a recessed landscape design element that creates a vertical barrier while preserving an uninterrupted view of the landscape beyond.
The design includes a turfed incline which slopes downward to a sharply vertical face, typically a masonry retaining wall. Ha-has are used in landscape design to prevent access to a garden, for example by grazing livestock, without obstructing views. In security design, the element is used to deter vehicular access to a site while minimizing visual obstruction.
The name "ha-ha" may derive from the unexpected (i.e., amusing) moment of discovery when, on approach, the vertical drop suddenly becomes visible.
Before mechanical lawn mowers, a common way to keep large areas of grassland trimmed was to allow livestock, usually sheep, to graze the grass. A ha-ha prevented 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 ha-ha fit well with Chinese gardening ideas of concealing barriers with nature, but its European origins predate the European discovery of Chinese gardening.
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 (picket-style fence made of wooden stakes) 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 today 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 théorie et la pratique du jardinage (1709), which the architect John James (1712) translated into English:
"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—someone says "ha ha" or "ah! ah!" when they encounter 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 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."
During his excavations at Iona in the period 1964–1974, Richard Reece discovered an 18th-century ha-ha designed to protect the abbey from cattle. Ice houses were sometimes built into ha-ha walls because they provide a subtle entrance that makes the ice house a less intrusive structure, and the ground provides additional insulation.
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 0.6 m (2 ft) (Horton House) to 2.7 m (9 ft) (Petworth House).
An unusually long example is the ha-ha that separates the Royal Artillery Barracks 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.
Remains of the original ha-ha wall at Beechworth Asylum from the "outside" of the original asylum boundary
From the inside, the ha-ha was a barrier to passage
End view at the beginning of the remains of the ha-ha at Beechworth Asylum, showing the sloping trench
Ha-has were also used in North America. Only two historic installations 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 21st-century 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 prevent large motor vehicles from approaching the monument. The temporary barriers were later replaced with a new ha-ha, a low 0.76 m (30-inch) granite stone wall that incorporated lighting and doubled as a seating bench. It received the 2005 Park/Landscape Award of Merit.
- 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 as 15 m (50 ft) deep, is called a hoho ("Like a ha-ha but deeper"), 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 lies face down in the ha-ha, but is not 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". Wells had lived at Petworth House (mentioned above) as the son of the housekeeper.
- In Edward Gorey's The Awdrey-Gore Legacy, a satire on overcomplicated murder mysteries, a ha-ha is one of the typical places where the body of a murder victim might be found.
- In Tom Stoppard's play, Arcadia, the ha-ha is discussed in relation to a 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 was once discussed with the heirs who would see them mature. He imagines how the placement of copper beeches against a "haha" 400 metres (1⁄4 mile) from the ballroom windows might look in thirty years.
- Jennifer Dawson's 1961 novel The Ha-Ha is named for this landscape feature.
In 3D surface plots
3D surface plots of f(x,y) functions with zero order discontinuities may exhibit ha-ha like features (see figure).
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- 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.
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- Horace Walpole, Essay upon modern gardening, 1780
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- Large and Associates website
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- Washington Monument (from the OLIN website)
- Monumental Security (from the American Society of Landscape Architects website, April 10, 2006)
- "Risk Management Series: Site and Urban Design for Security, , page 4-17". U. S. Department Security, Federal Emergency Agency.
- Annotations from Terry Pratchett's Men at Arms (from The Annotated Pratchett File v9.0
- Terry Pratchett - Snuff (2011) page 56. (Corgi Books ISBN 978-0-552-16675-1)