Christmas tree cultivation has shifted toward the production of higher-quality trees, increasing land quality expectations as well. Indeed, some species of tree, such as the Fraser fir, are unable to grow on low-quality, marginal farmland. Flat or gently rolling land is preferred to that with steep slopes and inclines, which is prone to erosion and fluctuations in fertility. Noticeable obstructions, such as rocks, fences or significant underbrush, are also undesirable. Like all crops and plants, Christmas trees require a specific set of nutrients to thrive. There are 16 elements crucial for growth; of those, three are obtained through air and water: hydrogen, carbon,
Trysting tree smooth bark. The 'Great Fraser Yew' may be as much as 700 years old and once served as the rallying point of the Clan Fraser members in times of trouble. Kelso, in the Scottish Borders has a 'trysting tree' which is connected with the annual Common Ridings. The locally famous trysting place of the 'Three Thorns of Carlinwalk', this being an old name for Castle Douglas in Dumfries and Galloway, are recorded in the Ordnance Gazetteer of Scotland. Robert Burns writes of a trysting thorn tree (see below) at the Mill of Mannoch at Coylton in South Ayrshire. A new