Hail update and Early blight time

After the hail -
In my previous post about the July 20 hailstorm that hit the west Denver Metro area, I promised to report back to you. Here is the one month update.

Squash came back fantastically. The crooknecks sent two branches to either side and grew abundant new leaves (photo left). They also have been producing well (photo right). Compare to the photo published in the July 23 post. If the growing points aren’t completely destroyed, it’s obvious squash has a notable ability to bounce back.

The tomatoes are also on the rebound and maturing fruit especially the ‘Sweet Tangerine’ (see photo left). These annual vegetables have amazing resilience to plant-damaging hail events. Patience and water soluble fertilizer applications as discussed in the July 23 post can salvage a partially destroyed garden.

Early blight time -
Late summer is early blight disease time in the tomato plot. Infected leaves develop ½ inch, irregular brown target-like spots (photo below right - click photo to enlarge). As this fungal disease progresses, spots grow together causing lower leaves to yellow and drop. If severe enough, defoliation leads to fruit sunscald and decreased production. Warm temperatures, abundant rainfall, overhead irrigation, and high humidity promote disease development.

Fungal spores are splashed from overwintering plant debris and infected tomato family weeds such as horsenettle and nightshade. Volunteer tomato plants that sprouted from last years stray fruit left overwinter also can carryover the disease.

Manage the disease by eliminating volunteer tomatoes. Properly fertilize plants with nitrogen. Late season nitrogen deficiencies stress plants, making them more susceptible. Avoid working around tomatoes when leaves are wet. Brushing leaves can bruise them and the water aids spores in germinating and moving into leaf tissue. Irrigate at the base of plants rather than wetting leaves. Apply sulfur dust to protect uninfected foliage against infection. And finally, be sure to clean up garden debris thoroughly this fall.

While early blight can be manageable in late summer gardens and fruit can mature before frost, severe cases can limit production.

Appreciation is extended to Mary Small, Jefferson County CSU Extension Plant Clinician, for disease information.

[Photo credit Carl Wilson: Squash leaf recovery and squash fruiting 1 month after hail, ‘Sweet tangerine’ tomato fruit with white hail nicks visible on plants, early blight target spots and yellow leaves on tomato.]

When to harvest?

At a community garden recently I was asked when eggplant was ready for harvest. It’s particularly tough to know when to pick vegetables you are growing for the first time and perhaps rarely eat.

Most fruiting and many leafy vegetables are not grown until maturity but are picked when sweet and tender. It’s really a balance between allowing more time to produce greater yield versus the best quality. In my mind, quality and flavor for fresh eating win out unless vegetables are being grown for drying (beans) or preservation.

For fruiting crops such as squash, peppers, eggplant, tomatillo and okra, keep in mind that you generally want to nab fruit before seeds fully form. Once seeds form the plant quits producing and the fruit structure begins to toughen or break down.

Cob and pod vegetables should be harvested before sugars are converted to starch. If corn is allowed to go too long by even a few days, fresh eating quality suffers dramatically. Pods of peas, beans and okra become fibrous and toughen. Asparagus should also be mentioned for developing fibers if not picked early.

The hardest thing for me to see is summer squash and cucumbers left to grow large (yellow straightnecks nearing overmaturity photo above). They should be cut young before seeds fully develop. This also keeps squash and cucumbers coming. Do allow winter (also called fall) squash to develop tough skins and seeds. Maturity also develops the flavor of the flesh. Yields will be reduced but this is the compromise with winter squash.

Unless you like green tomato dishes, tomatoes are best ripened to full color on the vine. Peppers picked green promotes more. When allowed to develop red color and seeds, production of more peppers slows. Eggplants can be harvested when only half their mature size and shiny. Dull skinned fruits often have turned bitter and woody (harvest soon in photo right). Tomatillo husks will change color from green to tan. Greener fruit has more tartness than fruit allowed to develop a yellow color.

Leafy salad greens can be harvested when leaves are small and tender. Once seedstalks begin to form, it’s too late as bitterness and toughness have already set in. While outer leaves of Swiss chard, looseleaf lettuce, spinach and kale can be removed in installments to promote more growth, this only works for so long.

Heading greens such as lettuce should have developed firm heads. Cabbage is best harvested loose in summer. Save development of firm heads for fall and winter cabbages (photo left).

Root vegetables can be harvested small (new potatoes and young beets) or allowed to grow to size. Do not allow to oversize and become woody (carrots, beets and turnips) particularly in summer. In fall these roots will keep longer in cool soil before harvest. Parsnips in fact develop better flavor when harvested after frost and store well in the garden.


Photo credits: squash, eggplant and cabbage - Carl Wilson

Summer vegetable watering

The question of how much to water or how often to water vegetable gardens is a loaded one. There is no one answer because of variations in soil type, how well the gardener has increased the organic matter through amendment additions, temperature, wind, plant spacing and competition, mulched or not, rooting depth and other factors.

Studies show that gardeners tend to overwater. It’s possible to overwater even with drip systems by letting them run all night instead of an hour or two. The misconception seems to be “it obviously takes a long time to apply enough water because the water drips so slowly.”

Tomatoes, pepper and eggplant have a lower water requirement than many vegetables. Overwatering and underwatering both cause blossom end rot of tomato and pepper fruit. Keep soils medium moist but allow soil to partially dry down between waterings. The most critical time to water is during flowering and fruiting. Blossom drop is sometimes experienced in hot, windy weather, in spite of adequate watering. Avoid the temptation to overwater in these circumstances.

Water stress on corn will delay silking but not tassel development. This causes poor pollination of ears when pollen is shed from tassels before silk appears. The pollination problems from water stress causes poorly filled ears or stunted ear development.

Beans require more frequent irrigation than most other vegetables for optimal production. Beans in the blossom and fruit growth stages use the most water of any vegetable. Depending on temperature and wind, beans may use one-half inch or more of water per day. Blossom drop and reduced bloom indicate that beans have been too dry at some time. Even with adequate soil moisture, hot winds can cause beans to drop their blossoms. Tadpole-shaped beans (plump on one end and skinny at the other) are another symptom of past water stress.

An even-moisture supply throughout growth enhances the flavor of leafy vegetables. Cabbage family crops like broccoli and cauliflower develop strong flavors if allowed to become dry.


Water root crops consistently but note that extra water promotes excess leaf growth at the expense of root development. Excess water applied to root crops following a dry period will cause root cracking. Potatoes become knobby if they become too dry, and may decay in the ground if kept overly wet.

It’s probably obvious that the vegetable garden is no place to try to cut corners with water because moisture lapses decrease the quality of harvested vegetables. Avoid problems by consistent watering. Check soil by inserting a screwdriver or digging with a trowel and checking for a cool, damp feel that indicates moisture. Powdery soil that lacks a cool feel indicates dryness and that it's time to water. Checking the soil also avoids overwatering that decreases quality as well as wasting water.


Photo credits: Peppers, sweet corn, Swiss chard, red beets and carrots - Carl Wilson

Floating row covers and vegetable insects

A previous post discussed germinating seeds with the fabric dual-marketed as seed germination fabric and floating row covers. The fabric covers placed over the top of plants can serve several useful functions including shading plants when transplanting, and shading to extend the life of cool season vegetables as hot weather approaches. They are also used to capture heat for fall frost protection.

Row covers are easy to use. Throw loosely over plants allowing slack for future plant growth. You can also use covers over hoops or wire tunnels such as in the photo above right. Anchor to the soil with U-pins bent from wire and punched through the fabric that touches the ground. Soil also can be mounded over fabric edges to hold it down. Covers allow light and water through and stop movement of insects.

Looking at what insects are trapped under covers with vegetable plants and which are barred access is worthwhile. Row covers can stop plant damage from troublesome insects such as spinach leafminer, aphids, leafhoppers, cabbageworm and cabbage looper. Summer pest protection is offered against squash bug, cucumber beetle, bean beetle, corn earworm, whitefly and grasshopper.

Before declaring victory and thinking covers will solve all vegetable insect problems, remember that several insects spend part of their lives in the garden soil. When they emerge to find their favorite plant food enclosed in a cover that protects them from predator insects, they readily multiply. Examples are cutworms and slugs that lurk in scattered soil locations.



Some insects concentrate on the soil immediately around their host plant and can be thwarted by crop rotation. These include onion and seedcorn maggot, flea beetle, Colorado potato beetle, corn rootworm (left photo larva in soil and right adult on corn silks) and tomato hornworm. Planting in the same location and using floating row covers can set up insect problems with these plants.

If a pest does multiply under a row cover, it may be best to remove it to allow natural enemies such as lacewings and ladybird beetles access to the pests. Also remember that squash and other vegetables depend on insect pollination so be sure not to screen out bees during flowering.

Photo credits:
* Row cover over growing tunnel, David Whiting
* Larva of the western corn rootworm, Frank Peairs, Colorado State University, Bugwood.org
* Western corn rootworm adult on corn silks, Tom Hlavaty, USDA Agricultural Research Service, Bugwood.org

Coping with hail damage

The hail storms that pounded the west Denver Metro area and Englewood early this week and later the Castle Rock area have prompted this post. Some landscapes took golf ball sized stones. My own garden received a 15 minute dose of marble sized hail leaving only the skeletons of tomatoes (click photo left to enlarge white hail stones and plant destruction details).

First, hail is generally accompanied by an ample amount of rain so stay out of the garden. Wet soil compacts easily and tramping on wet ground only worsens garden problems.
Another reason to stay out of the garden is that plants are more resilient than you may think. Don’t let the damage discourage you.

Most vegetables are annuals and respond to hail pruning with new growth. The limiting factor is the amount of growing season left to them before frost. Brittle plants such as peppers and large-leafed plants like squash (photo right) suffer the most. Leafy vegetables will re-grow and yield, root vegetables are protected underground and survive, and fruiting vegetables generally suffer the most.

Tomatoes tend to surprise in their ability to come back. My hope is that by hedging my bets through planting some shorter season Early Girl and cherry tomato types, I will still realize something where longer season heirloom types will probably not produce. The deep, extensive tomato root systems in my raised beds will help plants recover. I’ll keep you posted on this hope.

Once the water dries and its time to water again, I’ll begin using a weak fertilizer containing nitrate-type nitrogen in the water. Nitrate nitrogen signals plants to grow.

I will also continue sowing mid-summer vegetables for fall harvest as discussed in the July 2nd post. It’s not too late. Though I’m by nature accepting of hail events as a given in Colorado gardening, the act of planting does help soothe a gardener’s psyche. Doing something productive and once again seeing the wonder of germinating seeds is always energizing. Chins up intrepid Colorado gardeners!

Photo credit: Hail damaged tomatoes and Hail damaged crookneck squash, Carl Wilson

The Challenges of Summer Sowing

Mid-summer sowing of vegetable seed can be a challenge due to weed competition and warm soil temperature.

Weeds germinate quickly in summer and it can be difficult to tell the difference between weed seedlings and vegetable seedlings. One tip is to clear the soil surface of weed seeds by germinating and eliminating them. A week or more prior to sowing, water soil to germinate summer annual weeds such as purslane (see photo below left) and crabgrass and foxtail (photo below right).













Next use a sharp scuffle hoe to cut off the weeds from their roots, disturbing the soil as little as possible. Deep penetration of the soil will bring up additional weed seeds to germinate. Once the soil surface is cleared of weed plants, sow small seeded vegetables at the recommended shallow depth. Use germination fabric over them during germination (see March 6 post for how).

Warm soil temperatures can be a concern for germinating some seeds. The maximum soil temperature for germinating lettuce and spinach is 70 degrees F. The optimum temperature for germinating peas is 70 and many other vegetables 80 degrees F. Seeds become dormant at high temperatures.

Tips for avoiding warm temperature dormancy are to water soil before sowing and sow in the late afternoon so germination will begin overnight when soils are cooler. Shading the soil with seed germination fabric also helps.

Another tip is to pre-germinate seeds. The pea seeds (photo left) were soaked overnight indoors at room temperature (70 degrees F) in a moistened paper towel enclosed in a plastic bag. Do not soak longer or delicate seedling parts will be damaged in planting.

Pre-germinating small seedlings is more difficult. Solve this through fluid seeding. Germinate small seeds on a moistened paper towel in a closed plastic container kept indoors at 70 degrees F. Don’t allow seeds to germinate for more than a few days, only until they just break out of their seed coat. Wash germinating seed off the towel into a sieve with a gentle stream of room temperature water.

Gently stir germinated seeds into pre-prepared fluid seeding gel. The gel is made by dissolving 2 to 3 tablespoons of cornstarch in boiling water and cooling to room temperature. Add the gel-seed mixture to a plastic bag, seal, snip off one corner and gently squeeze the gel onto moistened soil. Cover as recommended and use seed germination fabric to shade. Keep fabric in place until green seedlings are readily apparent. Remove fabric and water carefully until seedlings are growing vigorously.

Crabgrass, purslane and soaked pea seed photos credit – Carl Wilson