There are no hard and fast rules as to when should you repot alpline, but generally you should think of repotting every second year. The best time is early spring.
But you could also repot at any time when a plant starts to look faded despite proper feeding and watering. It may be ‘pot-bound’ – that is. the roots have become so congested that the compost has dried out and lost its capacity to nourish healthy growth.
Extra watering does a pot-bound plant no good, it simply erodes the compost, which may take on a greenish, decayed look. When the compost deteriorates, the plant deteriorates too. Leaves turn yellow; flowers are disappointing; new growth is painfully slow. But if you repot every second year, your alpines should never reach this condition.
Alpine bulbs are a special case. They always benefit from being repotted every year – especially the smaller forms of narcissus, tulip and crocus.
Bulbs left to their own devices, or fed in their old compost, often emerge erratically and make a patchy display