Bounded by the Small Caucasus in the north and east and by the narrow Ararat Plain in the south west, Armenia grows vines commercially at 400 to 1,700 m (1,300–5,580 ft), the elevation determining climate, which is dry and continental to dry subtropical, the annual rainfall being less than 500 mm/19 in. Summers are so dry that 85% of vineyards need irrigation. Winters are sufficiently severe for 85% of vineyards to need winter protection, and there is a risk of frost at both the beginning and end of the growing season. Only about 10% of vines are grafted, and roughly three vines in four are grown on a four-wire vertical trellis.