Desert shrub and desert grass, common to southern Arabia, are found in Oman, but vegetation is sparse in the interior plateau, which is largely gravel desert. The greater monsoon rainfall in Dhofar and the mountains makes the growth there more luxuriant during summer; coconut palms grow plentifully on the coastal plains of Dhofar and frankincense is produced in the hills, with abundant oleander and varieties of acacia. The Al Hajar Mountains are a distinct ecoregion, the highest points in eastern Arabia with wildlife including the Arabian tahr.