Where Kirkeby paints an internal landscape, Hockney is currently obsessed by a specific external one. Since 2005, he has been painting the gently folding hills and woodlands of the area around Bridlington in East Yorkshire — the scene of his boyhood holidays and the home of his mother and sister. This undemonstrative scenery has inspired an extraordinary fecundity in the painter: since the start of the project he has produced about 90 pictures a year, many painted en plein air on multiple canvases that are then put together to form an enormous whole. Perhaps he is in a rush to get these scenes down. 

Perhaps, too, he wants to create a body of work big enough to qualify him as a landscapist in the great tradition. A selection of 70 of these works is currently on show not in the North-East but in the exquisite Kunsthalle Würth in the old imperial town of Schwäbisch Hall, near Stuttgart (some of his landscapes created using a computer programme can also be seen at the Annely Juda Gallery in London). Hockney's approach is to paint the same view at different times of year, watching the seasons change and new elements reveal themselves. According to the artist: "You only notice things if you stay in one place for a time." So a copse is shown shivering naked in winter, flecked with buds in spring and fully cloaked in leaves in summer; cow parsley froths and fades in hedgerows; a wooded lane darkens as it becomes a tunnel of greenery and is then perforated by light as the leaves die back.

The individual canvases that make up these often wall-sized views are not a theoretical choice but a practical solution: they are the biggest he can put in his car as he travels to each site and the biggest he can get up his studio staircase. 

The pictures themselves are extremely decorative, painted in livid, unmixed colours but because he produces them in such numbers they lack depth and subtlety of handling. They show, however, the Californication of his native countryside — the bright palette of his adopted home applied to that of his youth. He is in the process of redefining East Yorkshire as Hockney Country (Drawing Board 2, pages 94-95).

Long's work is not about the appearance of landscape but about the landscape as material. For 40 years, on his walks around Britain, Africa, Central Asia and South America, he has arranged stones, slates and driftwood into geometrical shapes and photographed them. His lines and cairns appear like the ruins of ancient civilisations. 

Although Long pioneered a new, holistic approach to landscape, his pieces can sometimes seem staid when compared with the inventiveness of his fellow land artist Andy Goldsworthy. Heaven and Earth, a major retrospective at Tate Britain, offers a chance to gauge how Long's work now stands. It is a chance too to see four new mud paintings, worked with his hands on to the gallery's walls, and bringing indoors, in a more literal way than Kirkeby and Hockney, the very stuff of nature.