Greens crop replacement

Buckwheat seedlings following
harvest of spring lettuce crop

The onset of ninety degree F weather along the Front Range means those cool season greens that have lasted so long this year due to a cool May will soon be gone. The heat decreases quality (bitterness), long days induce bolting, and the crops days to harvest may have just ticked by.

What to do now? In late June to mid-July you can begin planting mid-season crops for late summer or fall harvest. Some crops tolerate heat well such as Swiss chard, bush beans and New Zealand spinach. Collards can be planted up to 3 months before frost by direct seeding. Root crops that mature in 50 days such as beets and carrots are also good bets.

With other vegetables it is best to chose heat tolerant varieties. With lettuce the Cos (Romaine) types as well as others noted for heat tolerance (such as 'Muir' cultivar Batavian type lettuce) can work. Note that lettuce seed has a natural thermal dormancy and seed may not germinate well at high temperatures. Pre-germinate seed, plant in cooler weather and use irrigation to cool soils to obtain germination.

Likewise with spinach look for heat tolerance such as in the Asian arrowhead types; one example is 'Flamingo' cultivar.

Keep in mind crop rotation when second cropping, rotating to a crop from a different plant family. In addition to edible crops, remember you can also utilize a summer green manure (soil building) cover crop such as buckwheat, Fagopyrum esculentum. Turn under in 30 to 40 days as it starts to flower to increase soil organic matter.

Photo credit: Buckwheat seedlings - Carl Wilson