Posts Tagged ‘transplanting’

Poor Stands or Stand Loss Due to Poor Seed or Plant Quality

Thursday, May 24th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

As spring planting season continues at a rapid pace, there are more reports of poor stands or stand losses in vegetable crops. The culprits are often soil insects or diseases; however, poor quality seed or plants can also be a source of the problem. You will most commonly see problems with poor quality plants or seeds when there is a cold period right after planting.

As we progress into the warmer part of the planting season, it is often assumed that late spring and summer plantings will not have stand issues as soil temperatures are warm and seeds should germinate and emerge quickly and plants should root out quickly if there is adequate moisture. With seeds, this is not always the case, especially if seed lots are of low vigor. Signs of low vigor seed will be abnormal appearance in the bag (shrivelled, cracked, off color, misshapen), small seedlings that emerge late or do not emerge at all, abnormal growth (twisting, snaking, or corkscrewing), small shriveled cotyledons in beans, small or distorted true leaves, swollen or split hypocotyls or coleptiles, and bleached out seedlings. Another issue affecting seed germination and emergence would be uneven or inadequately applied seed treatments (fungicides and insecticides).

Seed companies do a very good job of producing quality seed and most seed is produced in drier areas where seed diseases are limited. Once seed is harvested it is conditioned, treated, packaged, and stored. As seed is distributed it often goes through several phases of where it is handled and stored in different environments. Larger lots may be broken in to smaller units and then repackaged by resellers. Once seed arrives at the grower it will be stored and handled again, finally making it to the planter. In each new storage and handling activity, there is potential to do damage to the seed. Rough handling, high temperatures, and high humidity are particularly damaging to seeds.

Poor quality plants can be due to diseases or other pest damage. There are however other causes of quality issues in plants such as being poorly hardened off, overwatered, stressed, over or under fertilized, overgrown or leggy, over mature, or root bound. Chemical phytotoxicity can be another problem. As with seeds, improper plant handing can lead to quality problems including overcrowding in greenhouse and holding areas, rough handing of trays, and storing in light limited conditions for extended periods. Breaking plant stems plants, especially those that with excessive growth, is a common problem in transplanting as is damage to roots when pulling plants out of trays.

When troubleshooting stand losses it is important to consider these issues affecting seed or plant quality.

Transplant Shock

Friday, May 11th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

A number of watermelon fields have had issues with poor plant performance and plant losses after transplanting in the last 10 days. Transplant shock is most prevalent when there are cold, windy conditions after transplanting and when night temperatures drop below 50°F. Plant and planting conditions that increase the risk of plant shock include:

Poor hardening off. Plants that come directly out of greenhouses or that have just recently come out of houses are most at risk. A proper hardening off will include reducing fertilizer and water and exposing plants to outside conditions in a protected area. It takes a minimum of 5 days to harden off plants.

Different plant maturities. Younger plants are more susceptible to shock. In watermelons, pollenizers are often younger than seedless due to having more rapid growth. Pollenizers are often most susceptible to plant shock after transplanting.

Small root systems. Plants grown in small cell sizes have fewer roots and if rooting conditions after transplanting are not favorable, they will be at a higher risk of shock than plants with larger root systems.

Root bound plants. An opposite problem can occur where plants have been in trays too long and roots have become root bound. Root bound plants dry out more quickly and often do not send out new roots as quickly because many roots in the root ball have died or are growing in circles in the cell.

Root systems not fully formed. In cells of plant trays, if the plant has not produced sufficient roots, it will not pull out of the tray properly and roots will be damaged when extracting plants and plants will be more susceptible to shock.

Rough handling during transplanting. If transplant crews damage plants when pulling out of trays and when setting plants, there will be increased plant shock. This includes stem crushing or damaging roots when extracting plants.

Setting plants too low or too high. In the transplanting process, burying plants too deep where green stem or leaf tissue is below ground can lead to that tissue being exposed to rotting organisms. Conversely, if root systems exposed (set to high), they can dry out and cause plant loss.

Inadequate plant water. If there is inadequate water at transplanting, plants can dry out and losses can occur.

Too much fertilizer. Too much fertilizer in the transplant water or in beds near the plant can cause salt injury and plant losses.

Poor plant handling. Keeping plants in tight conditions such as plant trucks for long periods of time, in extreme heat conditions, or where they have no light for an extended period will weaken plants and when exposed to the direct sunlight after transplanting, losses can occur. Plants shipped in that have been in transit too long or where truck conditions were stressful (cold or hot) will have more risk of shock. Plants that have dried out before transplanting are also at risk.

Can Antitranspirants and Antidesiccants Improve Vegetable Transplant Survival?

Thursday, April 5th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Antitranspirants and antidesiccants are materials applied to plants to limit water loss. They have been used with some success in horticulture, especially in the ornamental industry. I was recently asked if they could be used to improve transplant survivability for vegetable crops. Research has shown some benefits, but results have been inconsistent.

Transplants most commonly desiccate when water loss exceeds water uptake. This commonly occurs in transplants because root systems are small, limiting uptake, and water loss in windy conditions or on hot days is high.

Remember that most water moves out of plants through regulated pores in the leaves called stomates. This is called transpiration. These openings have specialized cells that can open and close, depending on environmental conditions and plant internal signals. Controlling stomates and transpiration can reduce water loss and plant wilting.

Leaves also have waxy cuticles that limit non-stomatal water losses. However, in plants that have thin cuticles, in new leaves where cuticles are still forming, and under extreme drying conditions, such as high winds, water loss through the cuticle can be significant.

Antitranspirants/antidesiccants work in one of 5 ways:

1. Chemicals such as hexaoctadecanol, cetyl-alcohol and steryl-alcohol reduce transpiration by entering the leaf and forming a barrier from within to reduce transpiration loss of water.

2. Chemicals that are metabolic inhibitors such as PMA and DSA prevent stomatal opening.

3. The plant hormone abscisic acid (ABA) causes stomatal closure.

4. Wax and oil emulsions or chemical film materials such as di-1-p-Menthene prevent water loss by completely covering the leaf surface with a film. This limits losses through the epidermis and by covering part of the stomatal opening.

5. Reflective antitranspirants, most commoly clay based, reflect light energy thus reducing leaf heating and water losses. This is most useful for later plantings under heat load. It does not have much impact on wind desiccation.

Not all of these materials are registered for food crops so you need to read the label before using them on vegetables. The most commonly used with vegetables have been film coverings and reflective materials.

In addition to these materials, gels have been used to protect transplant roots. Transplants are dipped in the gels prior to planting and this can reduce root loss due to drying and thus improve the ability of transplant roots to survive, grow, and take up water.

In a 4 year trial with cantaloupes, researchers in Nebraska evaluated the effects of an antitranspirant (Folicote) sprayed on plants and a polyacrylamide gel root dip (SuperSorb) on early growth of transplanted muskmelon with or without windbreak protection. They found that “overall transplanting success and early growth were enhanced the most by wind protection, followed by the polyacrylamide gel root dip, and least by the antitranspirant foliar spray”.

Currently research is underway looking at the plant growth regulator ABA for height control of transplants and to improve early season survivability. It is being trialed in crops such as tomato and watermelon in several states. ABA is the plant hormone that controls stomates. Results have been encouraging and it may be labeled for this use in the future.

My base recommendation is that for maximum transplant survival you should produce compact, well hardened off transplants and provide wind protection at transplanting. Antitranspirants and antidesiccants are additional tools that can marginally improve transplant success.

Avoiding Failures with Early Planted Vegetables

Thursday, April 5th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

The mild weather has many growers eager to get an early start with summer vegetables. Early markets are often the most profitable with higher prices. However, growers should proceed with caution and realize that failures can occur if cold sensitive vegetables are planted when temperatures are sub-optimal. As we get back to more seasonable weather in April, there will be many nights ahead with temperatures in the 30s and frosts and freezes are still a concern.

Each vegetable crop has a minimal temperature at which growth will occur. Our summer vegetables such as tomatoes, peppers, cucumbers, watermelons, and squash simply do not grow if temperatures are in the 40s or 50s. Squash and cucumbers do not put on growth with temperatures below 60°F, cantaloupes, watermelons, tomatoes, peppers, and eggplants will not put on growth with temperatures below 65°F. If temperatures are below these minimums, plants will just “sit still” and will be at risk of cold injury, wind injury, and damage from early season insects and diseases. Cold soils will limit root growth, further placing plants at risk due to inadequate water uptake and the risk of desiccation. Excess cold can also stunt some summer vegetables so that they do not fully recover. This is especially true of cantaloupes.

When planting summer vegetables early, growers need to consider all the tools available to maximize heat accumulation and minimize heat loss. The following is a list of these tools:

  • · Use raised beds or ridges. Ridges that are oriented east-west with crops planted on the south side, will benefit from the additional heat accumulation from the increased solar radiation on that side. Sandy soils heat up quicker due to lower water content.
  • · Use planted windbreaks, most commonly rye, between beds or rows. Windbreaks reduce heat loss from cold winds and help to accumulate heat. Rye reaches full height by the end of April on most of Delmarva. Cold winds are the most damaging to summer crops. Sand blasting during dry wind storms can actually cut plants off at the soil level. Growers doing field plantings for early crops in unprotected areas should always use windbreaks.
  • · For direct seeded crops, choose cold tolerant varieties, plant shallower and into well drained soils, and choose protected fields for earliest plantings. Also till soils well ahead of plantings to allow for them to heat up. Plant as soon as soil temperatures are adequate for germination. Also choose seed that has high quality and performs well in a cold germination test.
  • · To warm the soil more quickly, use plastic mulches. Plastic mulches increase soil temperature and help hold heat during night periods. They can increase soil temperatures 5-20 F° depending on mulch color. In order of lowest to highest heat accumulation Black < Red < Blue < Olive/Brown < Clear in selecting mulches. Mulches should be laid tight on a firm moist bed that is clod free. This will allow for more effective heat transfer and accumulation. Loose plastic and cloddy soils will reduce plastic mulch benefits.
  • · Use clear poly plastic covers. Most commonly, these come with slits or perforations to vent excess heat. They can be placed over direct seeded or transplanted crops with wire hoop supports (low tunnels) or they can be placed over ridges with transplants or seeds planted in the depression between the ridges. Zip tunnels and vented systems, where clear plastic can be easily closed and opened, have also been used. High tunnels also use poly plastic for protection and heat accumulation. I will discuss high tunnel management further in additional articles.
  • · Use spun bond poly or woven poly floating row covers to insulate, frost protect, reduce wind, reduce heat loss from soils and beds, and accumulate some heat. They can be placed directly over low growing crops such as strawberries or can be used with wire supports for other crops. The insulation they provide can protect 2-8 F° depending on thickness. Usually a 0.9-1.2 oz. cover is used to provide protection but not limit light too much.
  • · For smaller plantings, use of additional heat sinks to absorb heat during the day and then release it at night can promote earliness. Heat collection devices are usually filled with water and may be clear or black plastic containers or tubes.

Combinations of these practices will provide greater cold protection, heat accumulation, and earliness. This could include plastic mulch + row cover, plastic mulch + clear row cover + floating row cover, plastic mulch + row cover + heat sink, plastic mulch + clear row cover + floating row cover + heat sink. Use of these combinations in a high tunnel will further enhance success with early planted summer vegetables.

Heat Damage to Vegetable Transplants

Friday, June 10th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Watch for heat damage in transplants on black plastic mulch planted recently. This is a common problem in later plantings of peppers and tomatoes in particular.

Vegetable transplants are exposed to high soil temperatures at the soil line around the transplant hole. I took soil surface temperatures in black, white and metalized plastic mulch in mid-afternoon this Thursday (June 9). The air temperature was 97ºF. In open planting holes at the soil line, the temperature was >130ºF in the black plastic mulch, near 120ºF in the white plastic, and less than 110ºF in the metalized (aluminum) mulch.

The stem tissue just at or above the level of the plastic will be killed at these high temperatures and the transplants will then collapse and die. Small transplants do not have the ability to dissipate heat around the stem as roots are not yet grown out into the soil and water uptake is limited. Another factor in heat damage is that there is little or no shading of the mulch with the leaves of small transplants.

In addition, high bed temperatures have the potential to damage roots.

There are a number of practices that can reduce heat damage in later planted vegetable transplants:

● Delay planting until a cold front goes through if possible.

● Use larger transplants with greater stem diameters and more leaves to shade.

● Make a larger planting hole, cutting or burning out the plastic.

● When transplanting into the plastic, make sure the stems of transplants do not touch the plastic once set.

● Water sufficiently in the hole to reduce heat load, the more water the better.

● Plant in the evening, once the plastic has cooled down, or in the very early morning.

● Switch to white or aluminized plastic mulch for later plantings. This will reduce the heat loading significantly.

● In smaller plantings you may paint the planting zone on the black plastic mulch white with latex paint and then plant through this white strip once dry. You can also mulch around the planting holes with wet straw to reduce heat loading.

● Use overhead irrigation after planting to keep the plastic cooler.


Early Transplanting of Warm Season Vegetables

Thursday, April 14th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

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. There has been a tendency to risk earlier and earlier plantings as growers try to hit the early market. Over the years, many of our early plantings of summer vegetables have suffered because of early cold damage and inadequate provisions to protect plants.

For early transplanted warm season vegetables choose the lightest ground that warms up quickly. 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. Rye windbreaks planted between each bed are desirable for early plantings because they limit heat transfer by wind. If no rye windbreaks have been planted, then consideration should be given to using row covers to protect the plants – either clear slitted or perforated low tunnels or floating row covers. Even where windbreaks have been used, row covers may be necessary for extremely early plantings.

Lay plastic mulch well ahead of time to warm soil. Black plastic mulch should have excellent soil contact. Firm beds and tight mulch are much more effective in warming soils. 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.

When producing transplants, use larger cell sizes and grow plants so that they have well developed roots in those cells for the first plantings. Large cell sizes will perform better than small cells in early plantings. 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.

Watch extended weather forecasts and plant at the beginning of a predicted warming trend. 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. 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. Extra caution should be taken to minimize root injury during transplanting. When transplanting, make sure that there is good root to soil contact and there are few air pockets around roots.

In years with cold, cloudy, windy weather after transplanting, we have had large losses of transplants in the field. It is critical to have warm soil conditions after transplanting to allow roots to grow out into the bed quickly. In cold, cloudy conditions, 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.

If cold weather occurs after transplanting, 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 and cucumber transplants may be temporarily stunted but generally grow out of the condition. Watermelons will hold if they have been hardened off properly. Cantaloupes can be stunted if exposed to excessively harsh early conditions. Peppers and eggplants will not put on any root growth until temperatures are warm enough. If stunting occurs on any of these warm season vegetables, you may lose the early advantage you were seeking. In addition, remember that all of these vegetables are susceptible to frost damage and will be killed by a late freeze.


Stem Girdling in Peppers

Friday, June 11th, 2010

It’s the time of year when we sometimes see pepper transplants with the symptoms pictured below.


This is sunscald injury on the stems of newly transplanted pepper seedlings, which is caused by stems laying against edges of black plastic mulch on hot, sunny days. Note that secondary pathogens such as Alternaria can infest bleached out areas of stems over time.

Transplant Shock

Thursday, May 13th, 2010

Gordon Johnson, Extension Fruit & Vegetable Specialist;

The first seven days in May in 2010 saw temperatures in the high 80s and even some night temperatures in the low 70s in Delaware, and while windy, it was not excessively so. Then came the weekend of the 8th and 9th where average wind speeds doubled or tripled followed by low temperatures the middle of this week with scattered frost at night. These weather conditions illustrate the perils of setting out warm-season transplants in the beginning of May and to the need to take actions to avoid transplant shock.

Transplant shock will be evident by severe wilting, drying of leaves and stems, and, in severe cases, full plant collapse and death. This should not be confused with diseases such as Pythium damping off or damage from seed corn maggot or other soil insects.

Many of our transplants come from southern producers this time of year and there is always the potential for transplant shock when they are removed from southern greenhouses with little or no hardening and then are shipped up to Delaware in unheated trucks, especially when temperatures drop in the 40s or below during transport. Locally grown transplants are also susceptible to transplant shock if taken directly from greenhouses to the field without a hardening off process. Even with good hardening off, 40 mph winds can quickly desiccate plants if set in the field, especially without adequate windbreaks.

As a reminder, 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.

Soil temperatures are a key factor in the establishment of warm season crops. It is important to lay plastic well ahead of planting and to have adequate soil moisture to absorb and then retain heat. When soil temperatures are too cold, root growth is minimal in these crops and root function is impaired. Water uptake is limited by low root activity and new growth and rooting-in is slowed. Root zone insects and diseases can further stress transplants and reduce stands in cold conditions.

To avoid transplant shock, make sure transplants have well developed root systems. Transplants should easily pull from trays and have full root balls. This is critical to avoid transplant shock. Do not rush transplants with poorly developed roots 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. 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.

It is important to plant so that soil covers the root ball and that the root ball is not exposed to drying. However, for crops such as watermelons and cantaloupes, make sure that soil does not surround the stem. Deep planting in cold wet soils will result in additional stress on melons. 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. If plants are not pulling well from trays and do not have intact root balls, plants will not survive adverse weather.

Avoid planting if weather conditions are unfavorable. Look at extended forecasts and plant on a warming trend where winds are not excessive. If heavy winds or very cold nights are expected, 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. If weather conditions are unfavorable, you may also consider using row covers to protect plants.

Windbreaks are critical for early plantings. Use windbreaks between every bed for the early plantings and have windbreaks between multiple beds for later plantings. This year, many of our windbreaks offer minimal protection due to poor fall and winter growing conditions. Where windbreaks are not adequate, delay planting until favorable weather is in the forecast.

Update on Alternatives if Fall Windbreaks Were Not Established for Spring-Planted Vegetables

Thursday, March 4th, 2010

Gordon Johnson Extension Fruit & Vegetable Specialist;

Due to the wet fall in 2009, many vegetable growers on Delmarva were not able to plant small grain windbreaks such as winter rye in fields slated for watermelons, cantaloupes, and other vegetable crops in spring of 2010. A special edition of the Weekly Crop Update was issued on January 25, 2010 ( with some options for spring planted windbreaks.

Snow melt and continued wet weather has caused further delays for potential spring plantings. The following are some updated recommendations for spring windbreaks when the weather breaks (hopefully in the next 2 weeks).

Windbreaks most commonly are planted between groups of 3 or more beds to reduce wind damage and sandblasting on young crops. Some growers have windbreaks between every bed to help trap heat and provide additional protection on early transplanted crops.

By mid-March, winter rye, wheat, or barley are not good windbreak options because they will probably not vernalize and produce stems. They will remain vegetative or short.

March-planted alternatives for windbreaks are spring oats, annual ryegrass, and tall mustards.

Spring oats, planted as early as possible, is probably the best option for March plantings. Use a high seeding rate (120 pounds per acre or more). Oats will provide good ground cover and will head in late spring. It will start to elongate in mid-May. While still not an answer as a full windbreak for early plantings it will reduce sandblasting and provide protection for later plantings. Height will be over 3’ at heading

Annual ryegrass will also produce significant growth from a March planting and provide soil cover. Plant seeds at a rate of 30 pounds per acre. Annual ryegrass can get as high as 3’ when producing seed heads but provides less of a windbreak. One concern is with annual ryegrass is that if it goes to seed it has the potential to become a weed problem in the future.

There are several tall mustard varieties that merit considerations as windbreaks from March plantings. As these mustards produce a flower stalk, they can reach a height of over 4’. They are often used as biofumigant cover crops. Varieties of these tall mustards include ‘Idagold’, ‘Pacific Gold’,’ Caliente 119’, and ‘Caliente 99’. These mustards flower 50-60 days after planting and can be over 4’ in height. Plant at 10-15 pounds per acre.

Mixtures containing 2 or more of the crops mentioned above (spring oats, annual ryegrass, tall mustards) may be more desirable as a late winter or early spring planted windbreak. Reduce seeding rates of each component by 1/3 in mixtures.

The University of Delaware Vegetable Extension Program will be doing research on windbreak alternatives for late-winter or early-spring planting in 2010. We are seeking on-farm cooperators. If you are interested, contact information is given below:

Gordon C. Johnson
Extension Vegetable and Fruit Specialist
University of Delaware, Carvel Research and Education Center
16483 County Seat Highway
Georgetown, DE 19947
General Phone: (302) 856-7303
Direct Phone: (302) 856-2585 x 590
Cell Phone: (302) 545-2397, Fax: (302) 856-1845

Heat Necrosis in Transplants

Thursday, July 3rd, 2008

Gordon Johnson, Extension Ag Agent, Kent Co.;

I have seen several cases of heat necrosis of transplants on black plastic mulch in the last two weeks. This is a common problem in later plantings of peppers and tomatoes in particular. Black plastic can heat up to well over 110°F on hot days in the late spring and summer. Vegetable transplants are exposed to these high soil temperatures at the soil line around the transplant hole. The stem tissue just at or above the level of the plastic will be killed at these high temperatures and the transplants will then collapse and die. Small transplants do not have the ability to dissipate heat around the stem as roots are not yet grown out into the soil and water uptake is limited. Another factor in heat necrosis is that there is little or no shading of the mulch with the leaves of small transplants.

There are a number of practices that can reduce heat necrosis in later planted vegetable transpants:

● Avoid using tender transplants that have not been hardened off.

● Use larger transplants with greater stem diameters and more leaves to shade.

● Make a larger planting hole, cutting or burning out the plastic.

● When transplanting into the plastic, make sure the stems of transplants do not touch the plastic once set.

● Water sufficiently in the hole to reduce heat load.

● Plant in the evening once the plastic has cooled down or in the very early morning.

● Avoid transplanting on very hot days or when extended hot, sunny weather is forecast.

● Switch to white or aluminized plastic mulch for later plantings. This will reduce the heat loading significantly.

● In smaller plantings you may paint the planting zone on the black plastic mulch white with latex paint and then plant through this white strip once dry. You can also mulch around the planting holes with wet straw to reduce heat loading.

● Use overhead irrigation after planting to keep the plastic cooler.