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

Heat At Last

New grape growth

The average May 2015 temperature in Denver was 4.1 degrees below normal at 53 degrees F. The cool month slowed or delayed growth of some plants and postponed planting of warm season vegetables.

This first week of June turned hot with temperatures in the eighties F. With this warmth grapes finally began to grow in earnest. The late start means flowers will likely escape frost when they come into bloom shortly. This is good news for looking towards fall harvest.

Transplants of squash
and pumpkin vine crops

With increased sunshine soils have warmed over sixty degrees F and vine crop vegetable transplants can be planted.

Warm weather also means it was time to add water to the side channels of Walls O'Water (WOW) to push the tops open. This turns the structure into more of a cylinder than a cone and allows for ventilation while still keeping the plant warm at night.

Wall O'Water with more
water added to open top
into a cylinder

Keeping the WOW on tomatoes or other warm season vegetables is likely wise for another reason. May and June are active storm months for Denver and the Front Range meaning not only rainstorms but also the possibility of hail. WOW offer fairly decent protection from hail.

An understanding of temperature, it's effect on plant growth and what can be done to temper it is a must for gardening success particularly at our high elevation.

Photo credits: Grape growth, Vine crop transplants, Wall O'Water - All Carl Wilson