There are a number of grass species with tightly packed flower spikes and they are commonly known as either foxtails and catstails for fairly obvious reasons! Timothy grass (Phleum pratense) is a catstail and is one of the most common of this group.
Timothy is also the tallest of these grasses and can grow to 1.5 metres (nearly five feet!) tall but normally, in my experience, about 1 metre is the usual height but this is still taller than similar species. The long cylindrical flower head can be about six inches long and this too sets it apart from its relatives. The flower heads are usually a greyish green in colour and are often at their best in June and July. The plant does have leaves, long thin pointed ones but it is the flower head that catches the eye.
Common in grassy places on all sorts of soils, and sometimes sown in pasture, it is widespread and may be encountered almost anywhere in Dorset
I was intrigued to know why it is called Timothy grass and the ever reliable Wikipedia comes to the rescue and suggests this is probably because an American farmer, Timothy Hanson, recommended the grass to British farmers in the mid 18th century and it subsequently became a major source of hay and cattle fodder .