Gardening Tips: Hail to the Hardy Greens Most garden greens can hardly wait for cool weather to come. They perk up and sweeten up as the mugginess of August fades away. Crops such as spinach, arugula, claytonia and mache, if protected by a cold frame or simple unheated greenhouse, survive the winter in cold climates, to be cut and re-cut for a continuous harvest. Sow them in September in the north, October in warmer parts of the country. They do best hunkering down, close to the earth. Lettuce and endive over-winter best when cut at baby leaf size rather than full-sized heads. Kale, collards and Brussels sprouts fare better if grown to full size and left outdoors to soldier on as long as they can, since they do not re-grow if cut back in winter. We can often harvest them for our Christmas table, even in snowy Maine.