Cool to Hot update

Flea beetles are a concern on tomatoes that were set out in May before weather was settled. These plants were stunted from the cold nights and have struggled to begin rapid growth even with the last week of hot weather.

Key to overcoming flea beetle feeding is to promote rapid growth of transplants and seedlings. Flea beetles jump from the soil and attack lower leaves first (photo right). If a transplant grows rapidly as did this tomato set out June 5 (see photo left), they overcome injury. For details and control suggestions for flea beetles that infest tomato family, cabbage family and other plants, see the CSU Extension fact sheet Flea Beetles.

Cilantro flowering has promoted more questions than usual this season. The quick change from cool to hot weather caused plants to rapidly develop flower stalks. Both temperature and day length influence flowering. In hot weather during the long days of summer, cilantro rapidly produces flower stalks with ferny foliage as opposed to the desireable flat leaves (photo shows both).

Plants induced to bolt produce flowers and set seed in four to six weeks from time of sowing. If you purchase transplants, they can quickly start to flower too. Grow plants in cooler shade to delay flowering. Sow a succession of cilantro seed every few weeks through the summer to produce a constant supply of the herb. In cooler spring weather, cilantro will keep in the leafy stage weeks to a month longer.

Note that if plants go to seed, you can make coriander spice from grinding the seed instead of harvesting cilantro leaves.

Photo credit: Flea beetle injury lower tomato leaves, Tomato transplant outgrowing flea beetle injury, Cilantro - All Carl Wilson

Hail NO!! - But for some unfortunately YES

June is always an unsettled weather month in between cool May and hot July. Hail has already been a worry for growers and some have already taken their licks. A June 8 storm nailed Ft. Collins and a short pelting got a vegetable project I'm working on in Denver on June 13.

Vegetables with broad leaves take it hard as evidenced by the broccoli photo right. Soil may also crust afterwards as seen in this photo from a clay soil northeast of Ft. Collins. With the heavy rains that frequently accompany hail, it is often best to stay off the soil until it dries out to avoid further compaction. There is little you can do at that point anyway. Once soil dries, cultivation to break up crusts may be helpful.

Hoops for low tunnels with floating row cover fabric at the ready may offer some protection if you're on the spot to pull up covers when hail threatens. If hail stones are large, fabric may be shredded and protection value likely decreases.

Patience is a virtue after a hail storm. Once it is time to water again, consider weak fertilizer in the water to add to the stimulus for new growth delivered by the hail pruning. If plants aren't responding after a few weeks, remember the possibility of early July seeding of the 50 to 60 day vegetables for fall harvest.

Vegetable plants are resilient following hail and growers can only imitate that quality.

Photo credit: Hail damage on broccoli, Soil crusting following hail, Low tunnels and row cover fabric - All Carl Wilson

To Mulch or Not

Vegetables are sensitive to environmental changes and the recent mix of hot and cold weather has had effects not just on transplanting warm season vegetables as mentioned last post. Some early season crops have already started to produce flower stalks. Remove and use the space to seed or transplant other vegetables maximizing production. Selecting a succession vegetable from a different plant family is good crop rotation practice.

If lettuce bolts for example, planting a rotational root vegetable such as carrot contributes to soil health as would adding compost before seeding. While carrots are easier to seed when weather is cooler, seeding is possible even in hot weather.

Carrots require 14 to 21 days to germinate. The chances of the seedbed drying out in this time are greater than with 7 days to germination seed. There is simply more time for something to go wrong whether it's windy weather or an irrigation problem that leaves soil dry.

Mulching with floating row cover fabric is one good solution for most seeded crops. To further increase chances of success with a many days-to-germination crop such as carrots, try doubling the mulch cover. Place grass clippings on top the fabric. Water easily percolates through both to wet the soil.

Periodically check under the fabric for signs of germination particularly once the 14 day mark approaches. Clippings are easily gathered when lifting the fabric and can be used elsewhere in the garden or in compost. Clippings alone generally are not used with carrots because they entangle with the ferny foliage.

As for mulching elsewhere in the garden in early June, definately avoid mulching peppers. It may be tempting to apply mulch during tranplant establishment but mulch delays soil warming. Wait until early to mid July to mulch peppers so soil thoroughly heats. This can make the difference between a good versus a poor or no harvest of peppers.

As for other warm season crops, it may be early to mulch them too. Efforts are probably better placed on proper watering and fertility to get plants established and hasten growth so they can outgrow flea beetle invasion that is common this time of year. More information on control of this insect can be found in the CSU Extension fact sheet, Flea Beetles.

Photo credit: Lettuce flowering, Seeding carrots, Double mulching with grass clippings over fabric - all Carl Wilson.