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