Posts Tagged ‘transplant production’

Transplant Disorders

Friday, April 29th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

This is the time of the year when county agents are called to look at disorders in transplants being grown in greenhouses and when samples routinely come into our offices for diagnosis.

There are many diseases of vegetable transplants that can start in the greenhouse – fungal, bacterial, and viral. Diseases should be considered first when looking at transplants. Insects such as thrips, aphids, and whiteflies also can be a problem in greenhouses and should also be considered as causes of injury. They can cause direct damage and can be vectors of virus diseases.

However, many vegetable transplant disorders are not cause by pests. Some of the most common are:

Excessive Stretch and Leggy Plants
This is most commonly due to too high of temperature differential in growing houses (wide differences between day and night temperatures), excessive fertilization (especially with ammonium N fertilizers), and excessive watering.

Irregular Growth
This can have many causes including differences in seeding depth, differences in tray filling, differences in watering, differences in location in the greenhouse, irregular heating in the greenhouse (hot and cold spots), and differences in media to name a few.

Salt Injury
Plant desiccation and injury due to high salts occurs commonly when fertilizer rates are too high or when dumping occurs from slow release fertilizers at high temperatures.

Leaf Scorching
his can be due to salt injury also, but can occur when plants that are overcrowded are then spaced and exposed to full light or when very tender plants are put out to harden off in windy conditions.

Nutrient Deficiencies
Iron deficiencies are common if media pH rises above 6.3. Calcium and magnesium deficiencies are common if media pH drops below 5.2. Nitrogen deficiencies from under-fertilization are also common and also where initial nutrient charge in the media runs out.

Stunting
Poor plant growth or stunting most commonly is due to lack of nutrients in the media (media is missing initial nutrient charge). It also can be due to excessively cold greenhouse temperatures.

Ethylene Injury
Crops grown in greenhouses with propane or gas-fired unit heaters that are malfunctioning can be susceptible to ethylene injury. Ethylene (C2H4) is an odorless, colorless gas that acts as a plant hormone. Symptoms range from misshapen leaves and flowers, thickened stems, stunted growth, flower or leaf abortion to stem curling and wilting.

 

 

Bacterial Fruit Blotch Detected in GA Watermelon Seedlings

Friday, April 29th, 2011

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

I just received word from Dr. David Langston in Georgia that bacterial fruit blotch (BFB) was confirmed on seedlings destined for shipment to other watermelon producing areas. Some plants may have been shipped before the outbreak was identified. At this time we do not know if any seedlings were shipped to Maryland or Delaware. However, increased scouting of transplants is warranted. Because BFB is seed-transmitted, locally grown transplants should also be examined.

BFB of watermelon is caused by the bacterium Acidovorax avenae subsp. citrulli. The disease is damaging because it causes large olive green to brown water-soaked lesions on fruit (Figure 1), making them unmarketable. Symptoms of BFB on seedlings are water-soaked areas of the lower surface of the cotyledons and inconspicuous lesions on leaves (Figure 2). BFB lesions will become necrotic often with yellow halos. Lesions are frequently delimited by veins. Infected seedlings collapse and die.

Conditions in greenhouse transplant houses are highly favorable for the development of BFB symptoms and the spread of disease. If BFB is suspected, please send plants to a diagnostic lab (University of Maryland or University of Delaware) for identification. In the meantime, destroy all trays with symptomatic plants. Remove adjoining trays to a separate – isolated – area for observation. Monitor these isolated seedlings daily and destroy trays where symptoms develop. After symptomatic plants and adjoining trays are discarded, spray the remaining trays with a labeled fungicide and continue applications until the plants are shipped or transplanted to the field.

Figure 1. Olive green water-soaked lesion on watermelon fruit. (Image courtesy David B. Langston, University of Georgia, Bugwood.org)

Figure 2. An inconspicuous lesion of bacterial fruit blotch on a watermelon transplant.

 

Producing and Sourcing Quality Transplants

Friday, March 11th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Transplant production is underway throughout the region. Cabbage, tomatoes, peppers, watermelons, cantaloupes, cucumbers, squash, lettuce, and even pole lima beans are commonly transplanted along with many other vegetables.

Producing quality transplants starts with disease free seed, a clean greenhouse and clean planting trays. Many of our vegetable disease problems including bacterial spot, bacterial speck, bacterial canker, gummy stem blight, bacterial fruit blotch, tomato spotted wilt virus, impatiens necrotic spot virus, and Alternaria blight can start in the greenhouse and be carried to the field. A number of virus diseases are transmitted by greenhouse insects.

Buy disease indexed seeds when available. To reduce bacterial seed borne diseases in some crops such as tomatoes, peppers, and cabbages, seeds can be hot water treated. Chlorine treatment can also be useful on some seeds as a surface treatment but will not kill pathogens inside the seed. Go to this factsheet for more details: http://ohioline.osu.edu/hyg-fact/3000/3085.html.

If possible, do not grow ornamental plants in the same greenhouse as your vegetable transplants and do not overwinter any plants in areas where transplants are to be grown.

For greenhouse growing areas, remove any weeds and dead plant materials and clean floors and benches thoroughly of any organic residue. Use a disinfectant applied to surfaces to kill pathogens. Choices are: quaternary ammonium products (Qam), chlorine bleach in a 1 part bleach to 9 parts water ratio, or hydrogen dioxide products. If possible, use new planting trays. If trays are reused, then one of these products should be used to disinfest trays. Bleach and Qam products require 10 or more minutes of contact to be effective.

One of the most important considerations is managing stretch or height of transplants. The goal is to have a transplant of a size that it can be handled by mechanical transplanters without damage and that have reduced susceptibility to wind.

Managing transplant height can be a challenge. Most growth regulators that are used for bedding plants are not registered for vegetable transplants. One exception is Sumagic which is registered for use as a foliar spray on tomato, pepper, eggplant, groundcherry, pepino and tomatillo transplants. See this past WCU article for more information http://agdev.anr.udel.edu/weeklycropupdate/?p=804. Research is being conducted on ABA products for transplant management and other products may be registered in the future.

For other crops alternative methods for height control must be used. One method that is successful is the use of temperature differential or DIF, the difference between day and night temperatures in the greenhouse. In most heating programs, a greenhouse will be much warmer in the daytime than nighttime. The greater this difference, the more potential for stretch. By reducing the day-night temperature difference, or reversing it, you can greatly reduce stem elongation. The critical period during a day for height control is the first 2 to 3 hours following sunrise. By lowering the temperature during this 3-hour period plant height in many vegetables can be controlled. Drop air temperature to 50° – 55°F for 2-3 hours starting just before dawn, and then go back to 60° – 70°F. Vegetables vary in their response to DIF. For example, tomatoes are very responsive, squash is much less responsive.

Mechanical movements over transplants can also reduce size. You accomplish this by brushing over the tops twice daily with a pipe or wand made of soft or smooth material. Crops responding to mechanical height control include tomatoes, eggplant, and cucumbers. Peppers are damaged with this method.

Managing water can be a tool to control stretch in some vegetables. After plants have sufficient size, allow plants to go through some stress cycles, allowing plants to approach wilting before watering again. Be careful not to stress plants so much that they are damaged.

Managing greenhouse fertilizer programs is another tool for controlling height. Most greenhouse media comes with a starter nutrient charge, good for about 3-4 weeks. After that, you need to apply fertilizers, commonly done with a liquid feed program. Greenhouse fertilizers that are high in ammonium forms of nitrogen will cause more stretch than those with high amounts of nitrate nitrogen sources. Fertilizers that are high in phosphorus will also tend to lead to stretch.

Exposing plants to outside conditions is used for the hardening off process prior to transplanting. You can also use this for height control during the production period. Roll out benches that can be moved outside of the greenhouse for a portion of the day or wagons that can be moved into and out of the greenhouse can be used for this.

Seedless watermelons have specific requirements: germination at high temperatures for 24 hours (to achieve even germination) then move immediately into a cooler greenhouse to grow out. See this past WCU article for more information http://agdev.anr.udel.edu/weeklycropupdate/?p=1714.

Many growers choose not to produce their own transplants but contract with greenhouse growers locally or in the South. Majorities of these transplants are of high quality and perform well in the field. However, each year, there are some shipments that have problems. The most common problem is transplants shipped before they are ready – without adequate root systems. These transplants will not perform well in the field, especially in earlier plantings. If possible, they should be placed in a greenhouse to finish growing before use.

Another issue is diseases. Bacterial diseases (such as bacterial spot), fungal blights (such as Alternaria or Gummy Stem), and viruses (such as Tomato Spotted Wilt Virus and INSV) have all been found in transplants at times. If a disease is suspected, have it quickly diagnosed and inform the Plant Industries section of the Delaware Department of Agriculture. Do not plant diseased plants in the field. Southern grown transplants are most often the source so make sure that you are dealing with a grower with a good reputation for producing disease free plants.

Plants that are shipped without trays (already pulled) or that are bare rooted that are packed tightly in boxes must be planted quickly. Delays will lead to plant deterioration, leaf loss, and potential disease buildup.

Seed Treatment and New Selected Fungicides and Bactericides Labeled for Greenhouse Use Tables in 2010 Recommendations Guide

Thursday, April 1st, 2010

Andy Wyenandt, Assistant Extension Specialist in Vegetable Pathology, Rutgers University; wyenandt@aesop.rutgers.edu

All seed used in transplant production as well as any transplants brought into the greenhouse should be certified “clean” or disease-free. Important diseases such as bacterial leaf spot of pepper and tomato can cause major problems in transplant production if introduced into the greenhouse. Bacterial leaf spot of pepper and tomato can be seed-borne and infested seed can be a major source of inoculums in the greenhouse and cause problems in the field later in the growing season. As a rule for any crop, any non-certified or untreated seed should be treated, if applicable, with a Clorox treatment, or hot water seed treatment, or dusted to help minimize bacterial or damping-off diseases. For more information on seed treatments for specific crops please see Table E-13 on page E46 in Section E of the 2010 Delaware Commercial Vegetable Production Guide.

An updated table for selected fungicides and bactericides labeled for greenhouse use is available in Section E of the 2010 recommendations guide. The table includes a comprehensive list of fungicides and biological agents approved for greenhouse use. Table E-14 can be found on pages E47-48 of the 2010 Delaware Commercial Vegetable Production Guide.

Greenhouse Sanitation and Inspection is Important for Disease Management in Vegetable Transplant Production

Thursday, April 1st, 2010

Andy Wyenandt, Assistant Extension Specialist in Vegetable Pathology, Rutgers University; wyenandt@aesop.rutgers.edu

Proper greenhouse sanitation is important for healthy disease free vegetable transplant production. Efforts need to be made to keep transplant production greenhouses free of unnecessary plant debris and weeds which may harbor insect pests and diseases. All equipment, benches, flats, plug trays and floors should be properly disinfested prior to use and efforts need to be taken throughout the transplant production season to minimize potential problems. Any weeds in or around the greenhouse structure should be removed prior to any production. Any transplant brought into the greenhouse from an outside source needs to be certified ‘clean’, as well as, visually inspected for potential insects and diseases once it reaches your location. Remember, disinfectants, such as Clorox or hydrogen dioxide products (Zerotrol-for commercial greenhouses, garden centers and Oxidate-commercial greenhouse and field), kill only what they come into direct contact with so thorough coverage and/or soaking is necessary. The labels do not specify time intervals for specific uses, only to state that surfaces be “thoroughly wetted”. Therefore labels need to be followed precisely for different use patterns (i.e. disinfesting flats vs. floors or benches) to ensure proper dilution ratios. Hydrogen dioxide products work best when diluted with water containing little or no organic matter and in water with a neutral pH.

Producing Quality Seedless Watermelon Transplants

Thursday, March 25th, 2010

Gordon Johnson, Extension Fruit & Vegetable Specialist; gcjohn@udel.edu

Watermelon transplants for early production are being started this week. Those destined for later field plantings will be started throughout the month of April. Growing quality seedless watermelon transplants requires attention to detail and conditions required are different than for seeded types. Common problems include incomplete germination, uneven growth, weak plants, and stretching (leggy plants).

Seedless watermelon production can be broken into 6 phases: seeding, initial germination, emergence, seed leaf stage to first true leaf, first true leaf to second true leaf, and hardening off.

Seeding
Trays with square cells at least 2 inches deep and 1 inch square should be evenly filled with a general greenhouse growing medium like Pro-Mix BX , Fafard #2, or Sunshine #1 (these all have a starter fertilizer charge). Do not use fine seed starter or plug mix types. Do not compress the media. Trays should be watered to capacity and then allowed to drain off excess for 24 hours. During this 24 hour period, trays should be placed in a heated area so that the media reaches a temperature of 85°F. Make planting holes 1” deep with a dibber and plant seeds with the pointed side up. Cover with a small amount of warm moist media just enough to fill over seeds in the holes. Do not water after seeding. Seeding should be done in a way that trays stay at 85° F (do not allow trays to get cold).

Initial Germination
Germination should be done in a room or chamber where temperatures can be maintained at 85-90°F and where there is high humidity. Uniform tray temperature is critical. This phase will last 2 day – trays should be kept in this high temperature growth area for 48 hours and no more. To insure even germination, it may be necessary to move trays around after 24 hours (trays on bottom shelves moved to top shelves and vice versa). In this phase the seed root will emerge but the crook that will carry the seed leaves above the surface should not be visible. If you see crooks, you have left trays in the germination area too long and you may experience plant stretch during emergence (if plants have emerged you are too late – stretch has already occurred).

Emergence
After initial germination, it is critical to move plants immediately from germination areas to the greenhouse for emergence. If you are having another grower germinate your seeds, it is important to schedule pickup or delivery so that there are no delays. Greenhouses should be set for 72-75°F day temperatures and 65°F night temperatures. Do not water until after you see emergence and even then water sparingly as needed to keep trays and emerging seedlings from drying out. Excess water and high greenhouse temperatures during the emergence phase will lead to stretch.

Seed Leaf Stage to First True Leaf
Maintain greenhouse temperatures in the 72-75°F day and 65°F night range during this period. Water moderately to keep plants from drying out but do not fertilize during this period (this assumes that the media you are growing in has a starter fertilizer charge). You want the plants to grow slowly for highest quality.

First True Leaf to Second True Leaf
Continue maintaining greenhouse temperatures in the 72-75°F day and 65°F night range during this period. You can fertilize once the first true leaf emerges. Generally 2 fertilizations of 100 ppm nitrogen concentration one at first true leaf and one at second true leaf will be all that is needed. If a constant feed system is used, set for 50 ppm nitrogen each watering once the first true leaf has emerged. These fertilization rates are for the media listed in the seeding section that contain a starter fertilizer charge. Avoid using fertilizers with high amounts of ammonium N as the nitrogen source as this can lead to stretch (use fertilizers with calcium nitrate and potassium nitrate as the main nitrogen sources). Avoid over-watering. Again, you want plants to grow slowly for highest quality.

(Some growers will use a media with no starter fertilizer charge. If that is the case, a different fertilizer program will be needed. Use fertilizers with calcium nitrate and potassium nitrate as nitrogen sources. Use 50 ppm N from emergence to first true leaf every 3 days, 200 ppm N every other day from first true leaf to second true leaf)

Hardening Off
It will take 4-6 weeks to finish transplants. Prior to transplanting, harden off plants starting one week before setting in the field. This is accomplished by lowering day time temperatures in the greenhouse (if greenhouses have side curtains roll them up during days if temperatures are not too cool). Reduce watering and stop fertilization. Some growers have the ability to place plants on wagons or move benches outside during the day, bringing them in at night. This is advised where possible but make sure the area is sheltered from high winds and avoid days where the temperature is below 60°F.

Pollenizers
The above information is for growing the seedless watermelons. Seeded pollenizers do not need special germinating conditions and can be grown directly in the greenhouse. The key is to time the production so that plants are produced and hardened off at the same time as the seedless types. They also should be grown slowly and attention should be paid to avoid stretch. Follow the same recommendations from seed leaf stage through hardening off.

Weather Conditions and Setting Out Transplants

Friday, May 8th, 2009

Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

This past week has been challenging and growers have been trying to set transplants between the rains. Weather conditions currently are not favorable for the growth of warm season vegetable transplants (watermelons, cantaloupes, tomatoes, peppers, eggplants, cucumbers, squash). We had some unusually warm weather from April 25-28 with average air temperatures in the 70s that allowed early plantings to go in on plastic mulch with promise of good establishment. From April 29 onward, average air temperatures have been mostly in the 50s and we have had rainfall every day from May 1 to May 7. This weather is expected to continue until Sunday. Next week promises some sun but temperatures will still be moderate.

Warm season vegetable transplants vary in their ability to withstand sub-optimal conditions depending on how well they have been hardened off and their inherent ability to withstand stress. Tomatoes, cucumbers, and squash are better able to handle early season stresses than cantaloupes, watermelons, or peppers. When temperatures are cool and soils are wet, growth is minimal in these crops. We often see problems, especially the first few days when sunny weather returns, with plants wilting. This is because root systems have not established or are not functioning well. Root growth is slowed in cold soils and low oxygen in water soaked soils will also limit root growth. Average soil temperatures need to be 65°F or higher under the plastic and average air temperatures should also be above 65°F (ideally above 70°F) for good establishment of these crops. Seed corn maggots and root diseases such as Pythium can further stress transplants and reduce stands.

The following are some considerations when transplanting warm season vegetables under suboptimal conditions:

● Make sure transplants have well developed root systems (transplants easily pull from trays and have full root balls); do not rush transplants into the field.

● Make sure transplants have been hardened off well by exposing them to outside conditions, eliminating fertilizer, and controlling watering well ahead of planting.

● In seedless watermelon systems, time production of pollenizer transplants so that they coincide well with the seedless transplants. Pollenizers are often planted a number of days after seedless because they emerge quicker. However, pollenizer root balls may not be well formed compared to the seedless transplants and they can suffer excessive losses in the field when planted in stressful conditions. The opposite can also be true if pollenizers are ready but the seedless plants do not have good root balls.

● Leggy plants will be a problem in stressful conditions and should not be used if at all possible. Leggy plants are more susceptible to damage in transplanting and wind damage after planting thus subjecting them to additional stress. Unfortunately, cloudy overcast weather often leads to stretch in transplants.

● Transplants should be planted at the proper depth. This is particularly critical for watermelons and cantaloupes.  There should be enough soil to cover the root ball of these crops but they should not be planted so deep so that the stem is covered. Deep planting in cold wet soils will result in additional stress on melons. Watermelons and cantaloupes should not be set deeper even if they are leggy.

● Extra care should be taken during transplanting during stressful periods to reduce injury to plants, particularly to root balls. Damage to roots will reduce establishment success especially in melons, cucumbers, and squash. Train planting crews so that they do minimal damage to transplants.

● Target lighter sandy soils that are well drained for planting in cold and wet periods. Leave out fields or sections of fields with low areas or areas that are excessively wet and plant them when more favorable weather conditions return.

● If plants will hold, it is best to wait until more favorable weather returns. Often there is no earliness gained by planting in the stressful period; or gains are negated by stand losses and the need to replant areas.

Sumagic Plant Growth Regulator Gets a Label for Some Vegetable Transplants

Friday, April 10th, 2009

Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

Sumagic (active ingredient uniconazole) is a plant growth regulator from Valent Professional Products used in greenhouse production for plant height control. It has received a label for certain fruiting vegetable transplants. This is the first plant growth regulator that has been labeled for vegetable transplants since food crops were pulled from the B-Nine label in 1989. Since then, transplant growers have had to rely solely on temperature, water, or fertility regulation to maintain compact plants and prevent leggy growth.

Sumagic is now registered for use as a foliar spray on tomato, pepper, eggplant, groundcherry, pepino and tomatillo transplants in the greenhouse (no other crops are registered at this time). The recommended label rate is 0.52 to 2.6 fluid oz per gallon (2 to 10 ppm) and one gallon should be sprayed so it covers 200 sq ft of transplant trays (2 quarts per 100 sq ft). The first application can be made when transplants have 2-4 true leaves. One additional application may be made at the low rate, 0.52 fluid oz per gallon (2 ppm), 7-14 days later, but you cannot exceed 2.6 fluid oz of total product (per 100 sq ft) for a season. Growers are advised to do small-scale trials on a portion of their transplants under their growing conditions before full scale adoption. Sumagic is registered for use on labeled vegetable transplants in all states except California and New York. However, the supplemental label must be in the possession of the user at the time of application. Go to http://www.cdms.net/LDat/ld836002.pdf for this supplemental label.

Vegetable Diseases in the Greenhouse

Friday, April 18th, 2008

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Many vegetable transplants are being grown in greenhouses across Delmarva. Potential for disease can be minimized in many ways:

  • *use certified tested and treated seed (even organic vegetable growers can treat with hot water or bleach solutions)
  • *walls, benches, hand tools, pots and trays should be sanitized with 5% commercial bleach
  • *weeds should be eliminated
  • *new (or sterilized) potting mix should be used
  • *seedlings should be watered early in the day so that the foliage dries quickly and, if possible, watered at the seedling base to reduce moisture on leaves
  • *provide good air circulation and exchange in the greenhouse to minimize periods of high humidity

However, even after careful sanitation and good greenhouse management practices, disease may develop. Most fungicides are not labeled for greenhouse use.

The following table, which is modified from the Vegetable Management Guide 2008-2009 New England Region, is a good summary of available fungicide options and the diseases that they manage. Please note that Ridomil is not labeled for use in the greenhouse. Use only labeled fungicides or biofungicides. Read the label carefully because if a product is not applied properly, phytotoxicity may occur.

Follow this link for the table: \”Fungicides and Bactericides Labeled for Vegetable Bedding Plants (pdf)\”

Cold Effects on Early Transplanted Vegetables

Friday, April 18th, 2008

Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

The frost we had this week should remind growers that as you try to get a jump on the growing season, cold weather effects need to be considered. Over the years, many of our early plantings of summer vegetables have suffered because of early cold damage and inadequate provisions to protect plants.

There has been a tendency to risk earlier and earlier plantings as growers try to hit the early market.

Earliest plantings of watermelons, cantaloupes, summer squash, and tomatoes will begin in the next 10 days. First transplanting of crops such as peppers and eggplant will begin in early May. One of the characteristics that all of these crops have in common is that they are warm season vegetables that are sensitive to cold temperatures, both in the root zone and above ground.

Considerations for early transplanted warm season vegetables:

1. Choose the lightest ground that warms up quickly for early plantings. Plant higher sections in the field first. Avoid areas that receive any shade from woods or hedgerows. Early fields should be protected from extreme wind and should not have frost pockets.

2. Lay plastic mulch well ahead of time to warm soils. Black plastic mulch should have excellent soil contact. Loose mulch is much less effective in warming soils.

3. Consider using IR plastics that trap heat (green and brown plastics). Clear plastics can be used but weeds are an issue and a good herbicide program will be needed

4. Make sure that there is good soil moisture when forming beds and laying plastic because soil water will serve as the heat reservoir during cold nights.

5. Careful attention needs to be paid to hardening off warm season vegetable transplants that will be planted early. Gradual acclimation to colder temperatures will reduce transplant shock. Do not transplant tender, leggy plants or plants coming directly out of warm greenhouse conditions for these early plantings.

6. Use vegetative windbreaks such as rye. This will reduce heat transfer by wind. Consider using windbreaks between each plastic bed in early plantings.

7. Consider using covers to protect from cold and wind and to increase accumulated heat. This includes slitted and perforated row covers and floating row covers.

8. Watch extended weather forecasts and plant at the beginning of a predicted warming trend.

9. Monitor soil temperatures in plastic beds and do not plant if they are below 60°F. Soil temperature in beds should be measured at the beginning of the day when at the coolest. When soil temperature conditions are not favorable, wait to plant.

10. Avoid planting in extended cloudy periods, especially if plants have come out of the greenhouse after an overcast period. These plants will not perform well.

11. When transplanting, make sure that there is good root to soil contact and there are few air pockets around roots.

Transplanted warm season vegetables vary in their ability to tolerate adverse weather after being set out. Tomatoes will stop growth but will grow out without much damage once warm weather returns. Summer squash also handles adverse conditions fairly well. Watermelons will hold if they have been hardened off properly. Cantaloupes can be permanently stunted if exposed to excessively harsh early conditions. Peppers and eggplants will not put on any root growth until temperatures are warm enough. Remember that all of these vegetables are susceptible to frost damage and will be killed by a late freeze.

In years with cold, cloudy, windy weather after transplanting, we have had large losses of transplants in the field. In many fields considerable hand labor was used to replace dying plants and in some cases whole fields were replanted. It is critical to have warm soil conditions after transplanting to allow roots to grow out into the bed quickly. What happens in cold, cloudy conditions is that plants shut down physiologically. Little root growth occurs and the existing roots on the transplant do not function well. If there is any wind, plants lose more water than they can take up and they die due to desiccation. This is accelerated when the sun does come out – the first sunny day after an extended cold, cloudy period is when you will see the most wilting of weakened transplants.

Later on in the growth cycle, cold weather during flowering can lead to problems with pollination and fruit formation resulting in reduced fruit set and malformed fruits.