Not to be semantically confused with : Cyprus [a country with similar name].

Not to be confused with : trees of the Genus Cupressus which are the true cypresses possessing larger mature cones and which generally take two years to mature rather than the one of those in the Chamaecyparis genus, such as Lawson's Cypress. Also, the twiggy sprays are not planar (as are those in the Chamaecyparis genus), but branch out three dimensions. True Cypresses include Monterey Cyprus (Cupressus macrocarpa), Mexican Cyprus (Cupressus lindleyi) and Italian Cyprus (Cupressus sempervirens). Monterey Cypress is planted in parks and gardens and is an introduced-naturalised species which self-seeds in Scilly, Jersey and Southern Ireland.

The specimen shown above growing in a garden in Walkden is probably the 'Lane' (1938) cultivar, which is common in small gardens since it grows to just 20m with yellower green leaves on the south side than is Lawson's Cypress (but a darker green on the sunless side) and forms a neat stumpy column. The specimen in Rydal is much taller and probably a true Lawson's Cypress.

Easily mis-identified as the hybrid Leyland Cypress (X Chamaecyparis leylandii) but the foliage of that does not hang downwards but is more upright. Also, the twigs are more stubby than those of Lawson's Cypress and, although dioecious, male or female flowers rarely develop. The (larger) ripe cone of Leyland Cypress has a conical wart in the middle of each scale which is absent on Lawson's Cypress.

Some similarities to : Nootka Cypress (previously Chamaecyparis nootkatensis another non-native cultivar planted in the UK but which has now been moved into the Xanthocyparis genus and is now called Xanthocyparis nootkatensis). This tree has very much more resinous and somewhat unpleasant smell when crushed, containing many terpenoids. The male flowers are yellow rather than the red of Lawson's Cypress.

It is not native to the UK but is native to Western USA and introduced into the UK in 1854 and is now common in parks and gardens. Many cultivars exist, some with glaucous blue-grey leafy-scales, others a golden or lime-green to rich-gold colour. In the USA it is known as 'Port Orford Cedar', 'Oregon Cedar' and 'Rose of Cedar' and the wood as 'Cedarwood' but it is not a Cedar!

It often sets seeds itself, as does Leyland Cypress despite the latters' reluctance to flower.

The volatile fractions of the tree contains the acetate of the ralatively rare sesquiterpenoid Oplopanone, as well as the diterpene hybaene (which must have another name since your Author cannot find the structural formula for this), amongst many other compounds.

A total of 66 compounds representing 99% of the oil have been identified in the essential oil, mostly monoterpenes rather than sesquiterpenes. Limonene is quoted as being the main constituent of the oil, accounting for 77.7% of it. The others are p-cymene-7-ol (3.0%), Myrcene (2.4%), Camphor (2.1%), δ-Elemene (1.6%), Oplopanonyl Acetate (1.6%), Methyl Perillate (1.3%), Terpen-4-ol (1.0%) and β-Oplopanone.

The latter figure of 77% for Limonene seems very high compared to another source which lists the constituents of the Essential Oil as:
14.3% α-Terpenol, 8.2% δ-Cadinene, 6.5% α-Pinene, 5.9% Camphor, 5.5% α-Fenchol, 5.3% α-Cadinol, 4.7% Fenchone, 4.2% α-Muurolene, 3.4% Tau-Cadinol (which is a stereoisomer of α-Cadinol), 3.3% β-Terpenol, only 2.7% (+)-Limonene, 2.7% Tau-Muurolol (another stereoisomer of α-Cadinol) 2.3% Citronellol, 1.9% α-Amorphene 1.6% Terpinolene, 1.4% IsoPulegol, 1.3% Borneol, 1.3% Camphene, 1.3% Eucalyptol (aka p-Cineole, ) 1.3% p-Cymene, 1.0% p-Cymenene, 1.0% β-Elemene and 1.0% Myrtenol.

But your Author guesses it all depends upon the time of year the extract is made, where the tree was growing, amidst which other trees, the climate, and a host of other imponderable variables such as soil type and any symbiotic or unilateral association with particular underground fungi.