Wednesday, December 16, 2009

Grow your own chicons (Belgian endive)

Growing delicious salad greens in December in Colorado may seem a stretch to some but it’s not as far-fetched as it may seem. Belgian endive or witloof chicory will produce the tight shoots of leaves known as chicons through winter forcing. They are highly desired for gourmet salads and are used either alone or with other greens. They can also be lightly steamed and are high in vitamin C.

As discussed last post, this plant is another form of chicory, Cichorium intybus. Belgian endive requires a two stage production process. These plants are grown as a root crop during the summer (first stage), dug and stored cold for winter forcing (second stage). They require a little over 3 months for root production so plant in early July. Be sure to plant Belgian endive and not the endive/escarole/frisee seed discussed last post.

Roots can be dug after the first frost in fall depending on variety and maturity. Mature roots are 1 ¼ to 2 ¼ inches in diameter. The final harvest should be made by early December from beds mulched to avoid soil freezing. Trim tops back to 1 inch and store roots by planting in pots of dry soil or lined out in rows in open-top trays that are at least 6 inches deep and have drainage. Roots that are too long for the container can be trimmed from the bottom. Do not water after planting but make sure that soil touches all sides of the roots and air pockets are eliminated. Store in an uncovered coldframe or under an outdoor deck on a north or east side where temperatures will hold at 40 to 60 degrees F (cooler is better). Root cellars or unheated garages and garden sheds are other storage possibilities. Roots are often covered with perlite, sawdust or dry sand after soil temperatures have cooled. This keeps them cool but mulches them from extreme cold.

The mulch becomes necessary to the second stage growing process, forcing. Roots should be forced in the dark so the shoots remain yellow-white and develop a mild flavor. Light cause the shoots to turn green and taste bitter. Some home growers use a length of 4 inch diameter plastic pipe over a root planted in a pot, filling the 6 inch tall pipe with perlite or a peat-sand mixture. Containers can be watered by applying water to the soil surface at the base of the pipe and not through the top of the pipe. Keep roots moist for the 3 to 4 week forcing period. Good soil drainage is important so roots don’t rot. Harvest when shoots poke out the top of the pipe. With this pipe method, you can tip the perlite or peat-sand mixture out of the top of the pipe, lift the pipe off the shoot, and cut the chicon at the soil line.

Winter forcing can be done over time producing a stream of fresh greens. Limitations to production will be when storage becomes too warm and roots start to grow. Note that traditional varieties such as ‘Totem’ and ‘Witloof di Bruxelles’ are forced by the soil or mulch covering method in darkness. New hybrid varieties from Europe such as ‘Normato’, ‘Mitado’ and ‘Tardivo’ produce tight heads in darkness without the need for soil or mulch covering.

Photo credit: Witloof roots, Rasbak. Chicon, David.Monniaux.

Wednesday, November 25, 2009

Frisee – Gourmet chicory greens

Chicory (Cichorium intybus) is an interesting garden vegetable that has many forms and is known by many names including frisee, curly leaf endive, flat leafed endive or escarole, radicchio, Belgium endive, witlof and chicon. Qriginally from Europe, chicory is a weed in America with scattered plants growing in Colorado at 4000 to 7000 feet elevation. Many people think it is a native “wildflower” (see photo). It is often confused with blue flax which has one layer of petals instead of the double “wheel” of chicory flowers.

Of the selected forms for eating, the leafy vegetables include frisee sometimes sold by seed companies as Cichorium endivia. The frilly leaves (see photo) are used as a bitter fresh green in salad mixes. Flat-leafed endive (escarole) is more often used as a wilted or cooked green. Note that some people use the term frisee for frilly lettuce but lettuce is in a whole separate genus, Lactuca. The chicory group of plants is confusing enough without mixing the idea of lettuces in with them.

It’s entirely appropriate to be talking about frisee in late November as the greens are very cold hardy and can survive until early December particularly if mulched. Frisee is easy to grow in 45 days and can be planted in mid-summer for a fall crop, or in early spring as a cool season crop for harvesting before hot weather arrives. Some people blanch their crop by tying leaves in a bundle 3 days before harvest to deprive the inner leaves of light and change them to a light yellow color.

Next post will be about another fun thing to do with chicory plants - harvest roots and force the gourmet witlof (chicon) buds to grow in winter.

Photo credits: Cichorium intybus flower-Alvesgaspar, Frisee – Frank C. Muller

Thursday, November 12, 2009

Leftover vegetable seed storage

Many home gardeners end up with a few seeds in a seed packet or even unopened packets of seeds. Are they worth storing for planting next year?

A dry climate is ideal for storing many vegetable seeds. Life is extended under dry conditions even if seeds are stored at warmer temperatures of 70 degrees F and not 32 degrees F. Exceptions are bean and okra seeds that develop hard coats causing poor germination. Seeds will reach 4 to 7 percent moisture under the 20 percent humidity often seen in Colorado.

Here is a relative guide to the life expectancy of seeds stored under favorable conditions. Use it for deciding whether to keep or toss leftover seed.

Life expectancy in years
Bean 3
Beet 4
Broccoli 3
Brussels sprouts 4
Cabbage 4
Carrot 3
Cauliflower 4
Chinese cabbage 3
Collard 5
Corn 2
Corn salad (mache) 5
Cucumber 5
Eggplant 4
Endive 5
Kale 4
Kohlrabi 3
Leek 2
Lettuce 6
Muskmelon 5
Mustard 4
New Zealand spinach 3
Okra 2
Onion 1
Parsnip 1
Pea 3
Pepper 2
Pumpkin 4
Radish 5
Rutabaga 4
Salsify 1
Spinach 3
Squash 4
Swiss chard 4
Tomato 4
Turnip 4
Watermelon 4

Photo credit: Seed packets, Carl Wilson

Thursday, October 29, 2009

October snow dump

Did you lose your garden? Mine is somewhere under the 18 inches of white stuff in the photo left. What good moisture for us! In dry Colorado, you never object to moisture however it comes (even if you secretly wish it to be doled out a little more gradually). This snow event will probably end up yielding about 1.5 inches of moisture when it melts this weekend. It’s predicted to be in the 50s F so the white will be a passing thing.

In addition to the moisture, snow is a good insulator. I’m not too worried about my annual ryegrass cover crop (photo right) that is coming up or my kale and other fall crops. They should be fine and the moisture will give them a boost.

Gardening resurgence in New Zealand - Like us, gardeners in the southern hemisphere are getting on board the trend towards more vegetable growing in the worldwide recession. See the news from the “kiwis.”

Photo credit: Snow in garden and Annual ryegrass - Carl Wilson

Friday, October 23, 2009

Evaluate tomato performance

Before memories fade, now is the time to evaluate what tomato varieties performed well for you this season.

The tomato variety that performed best in my southwest Denver garden was ‘Yellow Taxi’ (64 days, photo left) This was followed by the widely adapted All American Selection, ‘Celebrity’ (70 days). ‘Large Red’ (heirloom 82 days), ‘Sun Cherry’ (58 days) and ‘Green Zebra’ (heirloom 75 days) were poor performers. All were sorely tested by the July 20 hailstorm that hit the western Denver Metro area. ‘Yellow Taxi’ and ‘Celebrity’ recovered and produced.

The cool, early summer this year affected all Front Range tomato gardeners. Longer season varieties struggled more than others. Keep in mind that if you have part day shade, your days to harvest becomes longer because it takes 1 ½ of your part shade days or so to chalk up one day on the published days to harvest rating. For you, choosing short days to harvest varieties is a must.

What tomato varieties performed well for you in 2009? Make your notes to guide your choices in future years. Share your experiences with our readers and help everybody. Do note your location in your comment.

Photo credit: ‘Yellow Taxi’ tomato fruit, Carl Wilson

Wednesday, October 14, 2009

Last plants left standing

Wow. It was a cold and sustained hard freeze the end of last week. The low in Denver October 9th was 18 degrees F. The high on October 10th was 26 degrees F and low that night 17 degrees F. Both the high and low temperatures for Saturday the 10th were record low readings for that date. The photo right is of kale and lettuce under an inch of snow in my Denver garden that Saturday.

Even with a day and a half of readings below freezing, some hardy vegetables amazingly survive. Lacinato kale and onions, Purple Vienna kohlrabi and purple cabbage (photos) are still going strong. So are lettuce, radishes and hardy herbs such as parsley (photo). The root vegetables underground are also fine.

Now is the time to be glad you made those early July plantings of fall crops. You can be enjoying your garden until Thanksgiving.

Photo credit: Kale and lettuce under snow, Lacinato kale and onions, Purple Vienna kohlrabi, Purple winter cabbage, Parsley - Carl Wilson

Friday, October 9, 2009

Cold doesn't end garden chores

I overheard someone in the barber shop say how quickly cold weather arrived this year. If you’ve lived in Colorado for very long, you know that the unexpected is the rule. The arrival of snow in the third or fourth week of September is not unheard of. I saw the first snow-rain here on October 8 this year.

The usefulness of covering plants will come to an end this week as night temperatures dip into the low twenties F and hard freezes prevail in most areas. Covers help with a few degrees under freezing but not with temperatures this low and repeated over several nights. Some of the hardiest vegetables such as kale, cabbage, peas and parsnips may survive. (Red Russian kale shown with frost on leaves above left, and two days later unharmed above right).

If you have automatic drip or spray irrigation for your garden, it’s time to be concerned about freezing of exposed backflow prevention devices. Until you are ready to get the water blown out of the device for winter, some precautions may be in order depending on how exposed the backflow device is (photo left). Wrap an old rug for insulation, pull a plastic yard bag over the wrapped device for waterproofing, and cinch with duct tape to prevent wind from ripping it off (photo right). This will generally get you by for a short period.

Do plan to remove killed tomato, squash and other warm season vegetable skeletons after a hard freeze. You can avoid overwintering many vegetable diseases and insects by doing a thorough fall cleanup.

Early blight fungus overwinters on diseased plants and some weeds. Remove diseased tomato plant debris and clear weeds from the garden. If the disease was severe, consider moving tomatoes to a new location next year if you have this option. The unusual bacterial spot seen this year also survives on plant debris.

Viruses that affect tomatoes such as Tomato spotted wilt and Impatiens necrotic spot cause yellow rings or spots on fruit. If you see these, remove plant debris because viruses survive in plants, not soil. Note that lettuce, pepper and weeds such as bindweed and nightshade will harbor viruses.

Thrips insects that spread viruses from plant to plant overwinter as pupae in soil crevices or on plant debris. Flea beetles that chew shotholes in leaves spend the winter as adults hiding under leaves, dirt clods and other protected sites.

Fall plant cleanup and fall tillage tend to disrupt all of these pests.

Photo cedit: Two kale (frozen and two days later) and two backflow preventer (open and wrapped) photos, Carl Wilson

Thursday, October 1, 2009

Extending the season in fall

The decision about what action to take with impending fall frosts can be complex. That’s probably why many simply throw a cover over their warm season crops (peppers in photo, tomatoes, etc.) and hope for the best.

The rhythm of the seasons with shortening days and cooler temperatures really speaks against fighting the trend. Harvesting tomatoes and letting them ripen indoors as discussed in the September 17 post may be a better choice in many ways. Cold temperatures destroy flavor and chilling injury decreases “shelf life” of the fruit leaving them open to decay. Room temperature indoors eliminates both problems.

Tomatoes will not be setting more fruit in cool temperatures so saving green plants is not productive from that standpoint. Concentrating on soil improvement by removing warm season plants to the compost bin and planting a cover crop as discussed last week may be a better use of a gardener’s energy.

Cool season greens planted in mid-summer (kale and mesclun in photo) tolerate frosts well. They may be more productive for the water applied in fall than warm season plants. Maturing root crops will also survive initial frosts and store well in the garden until dug for use.

Covers can perform well in radiational frosts experienced under clear nights. Cloth (photo left) will trap soil heat with the plants and is fine as long as it doesn’t get wet. Wet cloth loses heat due to evaporative cooling. Plastic traps heat and doesn’t have evaporative losses due to moisture but must be removed promptly the following sunny day to avoid cooking plants. Do remove any cover the next day to allow the sun to warm the soil again.

See CSU Extension Garden Note on Frost Protection and Extending the Garden Season for more extensive information including comments on use of space blankets and Christmas tree lights under covers.

Photo credit: Plastic to cover peppers, mid-summer planted greens, fabric covered tomatoes, all credit Carl Wilson

Thursday, September 24, 2009

Winter garden soil improvement

Vegetable garden soils ideally should contain 5% organic matter. If your soil is lacking, boost it during the winter season by planting a cover crop.

Cover crops are grown to produce green organic matter to turn under the soil. Along the Front Range, plant them from September to no later than mid-October. In addition to boosting organic matter, they prevent wind and water erosion over the winter, build soil structure and suppress weeds.

Legume cover crops can add nitrogen to the soil through the action of nitrogen fixing bacteria. It is good practice to buy rhizobium (beneficial root-associated or “rhizo” bacteria) and apply as specified if the seed is not rhizo coated. Rhizobium bacteria are specific for the legume species and are sold with a specific expiration date.

Broadcast the seed/rhizobium mix at the specified seeding rate and water to germinate. If irrigation systems are shut down, hand watering in the fall will help the crop establish before growth slows for the winter.

Winter ryegrass is often used alone as a cover crop (see photo). Winter rye/Austrian pea or a winter rye/hairy vetch mixture overwinter well in Colorado. Winter rye is a quick germinating and pioneering grass. Hairy vetch is a hardier legume than winter pea for the coldest areas. Seed winter rye and Austrian pea at 4 to 6 ounces per 100 square feet. Plan on 2 to 3 ounces of hairy vetch seed for each 100 square feet of garden area.

Note that these green winter plants are attractive to deer and geese. If they are well established prior to extreme winter temperatures, plants generally recover from winter grazing in spring.

When turned under, the decomposing green material can deprive spring vegetables of oxygen if not done far enough in advance of planting. Plan to mechanically till or hand spade under at least two weeks and better yet a month prior to planting. The legumes may have to be tilled several times to kill them and prevent resprouting.

Many gardeners do not have the land area to plant a cover crop for the growing season without depriving themselves of vegetables for a year. Winter cover crops solve that problem.

Consider planting a cover crop this winter to improve your soil.

Thursday, September 17, 2009

Pick and ripen tomatoes when frost threatens

While warm weather can linger well into September along Colorado's Front Range, temperatures can also drop unexpectedly. The earliest September freeze in Denver occurred on September 8, 1962 when the temperature dropped to 31 degrees F. I’m certainly hoping for a warm fall but will be prepared to mount a tomato “rescue” if things look dicey.

Covering plants to trap heat from the soil is often enough to get through a short one or two night situation. Extended days of cold particularly when accompanied by cooling moisture (rain or snow) are more problematic. In those cases, harvest fruit before the frost event and ripen indoors.

Pick fruit with even a hint of color. Also harvest green tomatoes with a glossy green appearance that are at least three-fourths of their full size. Remove stems. Wash fruit under a stream of water and allow to air dry on clean towels. Make immediate use of any damaged fruit and save only blemish free tomatoes for ripening.

Low humidity causes fruit to shrivel while high humidity promotes mold. Pack fruit one layer deep in cardboard boxes in a room out of direct sun. Another option is wrapping individual fruit in sheets of newspaper or waxed paper if you have problems with shriveling.

Some gardeners have success with hanging whole plants upside down in a shed or basement to let fruits ripen gradually. In our dry climate, fruit handled this way tends to shrivel from low humidity.

Monitor fruit condition every few days. Remove fruit that has started to spoil before rots move to adjacent fruit. Ethylene gas produced by ripening tomatoes is a ripening hormone. Remove ripe fruit from the immature ones to slow ripening. Allow ripe fruit to remain to speed ripening of the rest of your tomato harvest.

Green fruit will ripen in about two weeks at 65 to 70 degrees F and about 3 weeks at 55 degrees. Storage below 50 degrees F will result in fruit with a bland, off-flavor. Never store tomatoes in the refrigerator if you want full flavor.

Photo credit: Range of tomato maturities on vine and Harvested tomatoes in box - Carl Wilson

Wednesday, September 9, 2009

Tomato bacterial spot

Tomato fruit in home gardens and commercial fields in Denver and the northern Front Range have developed a black spot disease unusual for our area. Dark specks from earlier in the season become raised and scab-like as they enlarge. Sunken centers on older spots are common (see photo left). Spots are brown turning black and can appear blistered. The round spots can merge causing irregular-shaped patterns (photo on yellow tomato below).

Bacterial spot is caused by a Xanthomonas campestris pv. vesicatoria (X.c.v.) bacteria. It is something we seldom see in our area due to our dry climate suppressing most bacterial diseases. This year, the wet early summer and higher humidity favored it. If people overhead instead of ground irrigated they tended to help the disease. The widespread hail and heavy, wind-driven rains that inflicted injuries on plants helped disease spread via wound entry.

At this point there is no way to make the existing spots go away. Early in the season, avoiding overhead watering would have helped. Clean plant debris from gardens and fields this fall. Don’t save seed as it can survive that way. Rotate tomatoes and peppers (another host) to soil growing non-tomato family plants (disease survives in soil for up to 1 year). Eliminate weeds in the tomato/potato family.

Other measures to spray transplants after setting out probably apply to humid climates as we may see little or none of this next year if it is drier and overhead watering is avoided.

This outbreak is a good example of an environmental trigger (rain and humidity) setting off a disease rarely seen even though the host plant and likely the bacteria were present in past years.

Note that the fruit is edible although many people may prefer to remove the skin with the surface spot.

Photo credits: Sunken spots red tomato – Carl Wilson,
Merged spots yellow tomato – Robert Cox

Wednesday, September 2, 2009

Powdery mildew on vegetables

The telltale talcum powder look of powdery mildew infections is common on squash and pumpkin vines now. This disease can cause yellow leaf patches on some plants, and distorted buds, stems and leaves on others. Leaves may drop prematurely and flower buds fail to open.

Powdery mildew damages plants by decreasing photosynthesis and removing nutrients from the host plant. Infections weaken plants and leave them vulnerable to other pests. Mildews are host specific and the ones seen on the vine crops will not affect onions or fruit trees.

It is generally thought that plants in areas with poor air circulation are prone to infection. Mildews are different than many other plant diseases and don’t require wet leaves for infection. Warmth and adequate humidity are sufficient. Dense plantings hold humidity on calm days and are often enough to set off disease development..

Do plant vegetables in full sun as shade contributes to weaker plants and also longer moisture retention. Prune or thin plants to increase light and air circulation. Direct water on the soil and don’t wet plant leaves. Avoid excessive fertilizer that promotes succulent leaf tissue that is more easily penetrated by disease organisms. Look for powdery mildew resistant varieties if available.

Most fungicides are preventives meant to be applied before disease appears or at least in the early stages. Examples are sulfur and potassium bicarbonate (sold as Remedy). Read label directions before application. With sulfur, be mindful that it can damage some melon and squash varieties. Do not apply sulfur when temperatures are at of above 90 degrees F or plant injury can result. In the photo right an eradicant stopped the disease and weather conditions were unfavorable for development so new growth is unaffected.

A few fungicides can kill existing mildew infections (eradicants) but are still best applied at the earliest sign of disease. The natural Neem plant-based fungicides (Greenlight Powdery Mildew Killer) and horticultural oils are eradicants. Don’t apply oil to drought-stressed plants or within two weeks of a sulfur spray application. Don’t spray oils at temperatures at or above 90 degrees F.

Thanks to Mary Small for information used in this post

Photo credit 4 powdery mildew photos, Carl Wilson

Thursday, August 27, 2009

Winter squash and pumpkin fun

As summer moves into fall, peek in your neighbor’s gardens and see what type of winter squash and pumpkins they’re growing. They are often standouts for their color and size. I ran into this pumpkin and Turks turban squash arbor (photo) that looked like a space saver. Grow vines vertical rather than horizontal! The centuries old, flat, French “Cinderella” pumpkins (Rouge vif d'Etampes) are also fun (see photo). Now is probably the time to remove any new fruit set on winter squash and pumpkins so existing fruit can mature.

These vines need lots of space to have the many leaves needed to produce enough energy to grow these large fruit and generally require 90 to 120 days to grow. The gardener in this photo is fighting to keep her window wells from being covered by a pumpkin vine. Certain winter squash do come in bush or semi-bush varieties (acorn, butternut, delicata). Vine tips can be pinched to keep vines in bounds but will limit production and quality. It’s better to find a spot with room such as this streetside gardener (photo).

Winter squash differs from summer squash in that it is generally harvested and eaten in the mature fruit stage. Vegetable spaghetti (photo) is probably an exception often being harvested in a semi-mature stage (harvest when the skin turns from green to buff). Pick most winter squash when the skin has hardened into a tough rind not easily dented with light fingernail pressure. The seeds within should have matured unlike the young tender seeds in summer squash. When ripened to maturity, fruits of most varieties can be stored for use throughout the winter.

Winter squash are harvested in September or October, before heavy frosts. Carefully cut squash from the vines, leaving two inches of the often-woody stem attached if possible. Avoid cuts and bruises to the fruit when handling. Fruits that aren’t fully mature, are injured, have had their stems knocked off, or have been subjected to heavy frost won’t keep. Use as soon as possible or compost (watch for seedlings in the compost).

Squash are best stored dry at a temperature between 50 and 55°F. Don’t pile squash more than two fruits deep. Single layers that don’t touch prevent rots from spreading through fruit.

Don’t forget that squash and pumpkin seeds can be dried in a dehydrator or roasted for a healthy snack. When scooping out seeds to use the fruit, wash clinging fibers from the seed and dry or roast.

Photo credits: Squash arbor, Turks turban squash, Cinderella pumpkin, Pumpkin vines over window well, streetside pumpkin garden, vegetable spaghetti squash – Carl Wilson

Wednesday, August 19, 2009

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.]

Wednesday, August 12, 2009

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

Wednesday, August 5, 2009

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

Thursday, July 30, 2009

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,
* Western corn rootworm adult on corn silks, Tom Hlavaty, USDA Agricultural Research Service,

Thursday, July 23, 2009

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