It is the red tones that make this painting so memorable. Mondrian addressed the theme of trees in many artworks between around 1905 and 1913, but few carried such a bright colour scheme as this. Most likely, he put together the branches and trunk in darker tones before then adding the red brushstrokes afterwards. We can see colours from behind showing through which confirms this. He then continued the colour on the ground, with small single strokes of the brush which help to create a consistency throughout the composition. The area below the tree is generally lighter, where a traditional shadow has not been used. This is an expressive work, where new principles can be used and Mondrian was not constrained by the styles of the past.
If we look at the artist's work during 1908 we can find that colour was his key concern. He produced a number of study drawings for this particular painting in order to correctly put together the elements of the tree, but he would also have been thinking about the right colour combinations for the final painting whilst doing so. We also find a general development towards greater expression and abstraction within his tree paintings, which is confirmed by several items from a few years later, where the trees were barely recognisable, such was the lack of realistic detail being used by that point. Gray Tree shows a midpoint within that process, where form is still reasonably well represented but we can also see abstraction coming in for the first time.
Some art historians have drawn comparisons between the style of this particular painting and many works from the great Dutch Post-Impressionist, Vincent van Gogh. It was specifically elements of the brushwork and also the reduced palette which leads to these comments, and this was part of an overall movement towards a newer form of art, and an increased use of emotion and personal feelings within a painting. Both artists found huge inspiration from nature, completing a number of landscapes and individual depictions of trees, such as Avond (Evening): The Red Tree. Their colour schemes would also tend to be bright, sometimes in an unnatural way that might remind us of the Fauvist movement too.
This relatively small painting is under a metre wide and considerably less tall. If you want to see it in person, it is in the collection of the Gemeentemuseum Den Haag and will normally be on display, though check ahead just in case it has been loaned out elsewhere. This exciting institution focuses predominantly on painting since around the mid-19th century, with some impressionism and then a good number of artists from the 20th century. They remain faithful to their location, with a good number of Dutch artists including several more Mondrian paintings, plus others by Vincent van Gogh, Johan Jongkind, Pyke Koch and Charley Toorop. Beyond this nation, you can also see original art from the likes of Edgar Degas, Claude Monet, Pablo Picasso and Egon Schiele.