Cheap imported lamb from New Zealand may be available all year round, but in season local lamb is hard to beat. In May and June lamb is at its most tender but as the season progresses the flavour develops. Spring lamb is fantastic for roasting simply with garlic and herbs, autumn lamb is great when given a spicier, more adventurous treatment (see below for examples).
Sheep thrive in a variety of climates and have been the principal meat source across North Africa and Eurasia for centuries. The Industrial Revolution sparked an increased demand for meat and led to the increased breeding of sheep for meat. We can now reap the reward of several generations of selective breeding for taste and texture; well-reared lamb today is likely to be better than any eaten at any time in the past.
Lambs are the offspring of the domestic sheep, ovis aries. Lambs are typically weaned to a diet of grass between the ages of 1 and 3 months and the consumption of grass adds flavour to lamb. The meat of older animals is properly referred to as hoggett (up to approximately two years old) and then mutton (the categorisation of the meat is often based on the farmer's judgement of its qualities rather than its exact age).
Big supermarkets will source lamb from a number of different farms. Buying lamb from a good butcher's shop or farmers' market will give you the opportunity to ask about the source of the lamb, and then buy the same quality produce again if you like it. Look for firm, pinkish meat with creamy white fat.
Lamb can be kept in the fridge for at least a couple of days - the larger the cut the longer the meat will keep. Freezing tends to have a drying effect on meat and so is best used for cuts that will be slow cooked in stews or casseroles, rather than dry-heat methods (grilling, roasting, frying).
The cooking method will be dependent on the cut and recipe. Generally lamb benefits from slightly slower cooking with more moderate heat compared with beef. Trim excess external fat (or ask your butcher to do this) before use. Lamb cooked using dry-heat methods will be more flavourful if served slightly pink. Stews and casseroles will benefit from slow-cooking until no pink remains. When roasting larger cuts, allow the meat to stand for at least 15 minutes after cooking.
There are around 10 sheep per person in New Zealand and Kiwis are the world's biggest consumers of lamb.