"The Belgian Tervuren is particularly adaptable to extremes of temperature or climate. The guard hairs of the coat must be long, close-fitting, straight and abundant. The texture is of medium harshness, not silky or wiry. Wavy or curly hair is a fault. The undercoat is very dense, commensurate, however, with climatic conditions. The hair is short on the head, outside the ears, and on the front part of the legs. The opening of the ear is protected by tufts of hair. Ornamentation consists of especially long and abundant hair, like a collarette around the neck, particularly on males; fringe of long hair down the back of the forearm; especially long and abundant hair trimming the breeches; long, heavy and abundant hair on the tail. The female rarely has as long or as ornamented a coat as the male. This disparity must not be a consideration when the female is judged against the male." ---From the AKC Belgian Turveren Standard
Correct texture and undercoat, which protects the dog in the often wet and cold climate of its homeland, is more important than coat length in this functional breed.
The coat is long but should not be so excessive that it masks the desired silhouette of the body or interferes with the dog's practical usefulness as a herding dog. It is close-fitting, that is to say, the outer coat fits closely over the undercoat, protecting the dog from the elements. The dog should not be groomed in such a way that the coat stands out from the body.
Trimming should not be done except if desired for the feet, pasterns and, optionally, the whiskers (this is seldom done today).
Adult males characteristically will carry a more profuse coat. The collarette adorning the neck is particularly attractive when it frames the face and ears and gives an added arch to the neckline. Females generally go through a shedding cycle between each heat, and do not carry the coat length of the male, particularly the long collarette. They should never be penalized for not having the grand coat of a male, rather, it should be expected. The bitch's coat should be judged for its own unique vitality, beauty, and coat texture and be given equal consideration as the male. Notice the difference in coat length, particularly in the collarette, between the male (left) and female (right).