PICK OF THE BEST: COS LETTUCES
Ornamental and a great summer salad staple
IF you grow veg, it’s likely that you grow lettuce. But many gardeners are unaware of the vast number of different varieties that are available. We know there’s crisp, cos, butterhead, looseleaf… but that’s about it. Yet one seed company alone lists more than 50 different varieties and, within each of the four main types there’s a huge range – some of which are quite difficult to tell apart just by looking at them.
So what is the difference? And how, with more than 50 lettuce varieties boasting AGMs, do we choose?
This week, I’m looking at cos lettuce, sometimes called romaine. These are tall and narrow, with thick, crisp leaves and (often) a relatively loose heart. Crisp (or iceberg) lettuces have tight, crisp hearts; butterheads have smaller and softer heads and mature more quickly; looseleaf lettuce, meanwhile, do not produce a heart at all.
Cos have that distinctive, upright shape, plus darker outer leaves and paler leaves within, often with a thick midrib. Their flavour is different from that of other lettuces. They also take a little longer to mature but last longer without running to seed – especially in hot, dry weather or when you’re unable to water. And they keep longer than any other lettuce after cutting.
You can grow them as baby salad
leaves, and because they are hardier, cos lettuces can be sown earlier – some can even be sown in autumn, to overwinter for an early crop.
And what about baby cos, semi-cos or ‘Little Gem’? These are, basically, a small, tightly packed form of cos, with crisp, sweet foliage and, by most people’s estimation, the best flavour of all.
Mostly, cos lettuces are green; however some, including ‘Exbury’ and ‘Rosedale’, are a dramatic deep-red colour. Varieties are distinguished by their size at maturity, how quick they are to mature, how long they stand in good condition, disease resistance, resistance to tipburn, the density of the hearts and their crispness, along with their visual appeal in the garden. A lot to consider.
New varieties appear regularly as breeders incorporate increasing disease resistance. Consequently, many of the varieties awarded AGMs in the past have since been superseded and can be hard to find in catalogues. That’s why the AGM is so useful as a guide.