Growing Leafy Greens

By Laurel Aiello | Fort Collins Nursery

As temperatures dip, warm-weather crops produce their final harvest and cool-season crops begin to thrive. Plants that prefer lower temperatures (mid-50s to mid-60s) include broccoli, cauliflower, snap peas, Brussels sprouts, cabbage and root vegetables. Leafy greens also fall into this category, producing tasty superfoods even in light frosts. Here are five fan favorites that keep gardeners busy well into the fall.

Lettuce (Lactuca sativa)

There are dozens of lettuce varieties to choose from, each with their own taste, texture and maturity date. For example, romaine, iceberg and buttercrunch lettuce all produce large heads about 45-60 days after their seeds are planted, though they can be harvested earlier if smaller heads are desired. Many seed packets contain salad mixes that can be planted successively and harvested when they are tender and small, usually a few weeks after planting. In general, lettuce should be planted four-to-five weeks before the first frost. It thrives at 60-65° F; if it gets much hotter, the plant will sacrifice its crisp, refreshing flavor in order to flower and produce seeds, otherwise known as “bolting.”

Spinach (Spinacia oleracea)

Spinach is chock-full of nutrients, including iron, calcium and vitamins A, C and K1. It is a very cold-hardy vegetable, tolerating temperatures below freezing (especially if it is protected by a cold frame) and producing high yields of dark green leaves when temperatures stay between 60-65° F. Different varieties offer a range of leaf sizes, tenderness and flavors, from sweet to slightly bitter. Most reach full maturity within 45 days of sowing, and the leaves can either be cut from the stem or harvested at the base once a full rosette forms.

Arugula (Eruca vesicaria)

Known for its peppery flavor, this superfood is packed with vitamins, minerals and prebiotic fiber. Arugula grows well in cold conditions, with a sweet spot of 45-65° F, and it can grow through the winter under a cold frame. Plant rows of seeds successively (every week or two) so that they mature at different times, then pick the leaves once they’re a few inches long, about three weeks after the seeds were sowed.

Swiss Chard (Beta vulgaris)

Swiss chard is bitter when eaten raw, but once it’s cooked, it has a sweet taste similar to spinach. Rich in magnesium, iron, potassium and vitamins A, C and K, swiss chard is a nutritious addition to stir-fried vegetables, soups and colorful fall dishes. Direct sow the seeds a month before the first frost and harvest the leaves, beginning with the outer layer, when they reach 6-8 inches tall. Swiss chard can tolerate near-freezing temperatures, especially under a cold frame, and it thrives at 50-70° F.

Kale (Brassica oleracea)

Often used in smoothies and salads, kale contains vitamins A, B6, C and K as well as other essential nutrients. It thrives at 55–75°F and can be planted successively a month or two before the first frost, though mature plants will tolerate temperatures below freezing. Harvest kale leaves individually, beginning with the oldest leaves, or pull up the entire plant and trim off the roots.