Postharvest

Watering Phalaenopsis orchids with ice cubes

By Kaylee South and Michelle Jones

 

Orchids are the number one potted plant in the United States (USDA, 2016) with the Phalaenopsis orchid making up most of the commercial sales (Griesbach, 2002). These plants can be found in grocery stores and garden centers in different sizes and many different colors. Phalaenopsis orchids make great houseplants because their temperature and light requirements are compatible with the environment found in a home or office (Banks, 2005). There is no doubt why these plants are so popular with their beautiful flowers and glossy green leaves, but caring for an orchid can be intimidating to some consumers. One of the biggest challenges with potted Phalaenopsis orchids is proper watering. Ice cubes have historically been used to water containerized plants during trade shows, when access to water is limited and watering plants can be difficult, but can ice cubes be used on a regular basis to water house plants?

Why ice cubes? Green Circle Growers (Oberlin, Ohio) markets their Just add ice orchids™ with the recommendation that the orchids be watered weekly with three ice cubes. This recommendation has intrigued many and also raised some concerns about watering a tropical plant like orchids with ice. One goal of this recommendation is to increase consumer success with Phalaenopsis orchids by providing them with an easy way to deliver the right amount of water to their plants. In addition to being easy and convenient, the application of ice provides a slow release of water that is more readily taken up by the roots and retained by the bark media. When irrigated with water, much of the water that is applied runs through the bark and accumulates in the bottom of the pot. If orchid roots sit in water they can be damaged, and this can lead to the death of the plant.

Does ice cube irrigation cause damage to the orchid? Watering a plant with ice cubes, especially a tropical plant like orchids, may seem a little strange. It was therefore important to ask if ice cube irrigation caused any damage to the plant. Experiments were conducted at The Ohio State University and the University of Georgia to answer this question. Forty-eight Phalaenopsis orchids at both locations were evaluated for four to six months. Half of the orchids received ice cube irrigation and the other half received the equivalent amount of room temperature water. The flower life, root and leaf health, and temperature of the media were measured. The orchids irrigated with ice cubes had the same flower longevity (number of days individual flowers remained open) and display life (number of days from when the plant was received to when the last flower wilted on each plant) compared to plants irrigated with room temperature water. The leaf and root health determined by measuring chlorophyll content, photosynthesis, and shoot biomass were not negatively affected by ice cube irrigation. The temperature of the bark media during ice cube irrigation dropped to only 51 – 56 °F, and then returned to the original pre-irrigation temperature of 70 °F five hours after the application of ice cubes. The roots in the bark media were therefore not exposed to freezing temperatures. What about the aerial roots in direct contact with the ice? The internal temperature of roots directly exposed to ice cubes decreased to around 40 °F. Experiments on isolated root segments showed that Phalaenopsis roots did not show any damage from cold temperatures until they reached 20 °F, well below the temperatures they experience when exposed to ice cubes for 5 or 6 hours.

Can I irrigate my Phalaenopsis orchids with ice cubes? Yes! The results from the experiment described above show that ice cubes are a practical way to water Phalaenopsis orchids grown in bark media. The recommendation from Green Circle Growers we used during the experiment was three ice cubes, once a week. The ice cubes should be placed on top of the media, avoiding direct contact with the leaves. The water that remains in the bottom of the decorative pot should also be emptied to prevent damage to the roots. The amount of water needed by the orchid can vary in different cultivars and based on changing temperature, light, and relative humidity of the environment. Start with the recommended three ice cubes weekly, but monitor the plant to determine if this needs to be increased or decreased. Under-watered plants will have wrinkled, flaccid leaves. If the orchid is well-watered, the roots will have a green color, whereas when they are drier, the roots will have a slivery hue. Unhealthy, dying roots will be brown or tan (Cullina, 2004).

Where can I find more information about the experiment conducted? For more information on the experiments presented above, please follow the link below to the open-access journal article published in HortScience.

http://hortsci.ashspublications.org/content/52/9/1271.short

 

References:

Banks, D. P. (2005). Orchid grower’s companion: Cultivation, propagation, and varieties. Portland, OR: Timber Press.

Cullina, W. (2004). Understanding orchids: An uncomplicated guide to growing the world’s most exotic plant. Boston, NY: Houghton Mifflin.

Griesbach, R. (2002). Development of Phalaenopsis orchids for the mass-market. Trends in New Crops and Uses, 2000, 458–465. Retrieved from http://www.hort.purdue.edu/newcrop/ncnu02/pdf/griesbach.pdf

USDA-NASS. (2016). Floriculture crops 2015 summary. Http://Usda.Mannlib.Cornell.Edu/, (April), 1–59. Retrieved from http://usda.mannlib.cornell.edu/usda/current/FlorCrop/FlorCrop-04-26-2016.pdf

Preventing ethylene exposure and reducing ethylene production from plants during shipping and handling

Plants must be handled carefully during packaging and shipping to avoid mechanical damage. Wounded plants can produce significant levels of ethylene. Sleeving plants can also cause wounding. Make sure that the sleeving material has holes that allow the ethylene gas to diffuse away from the plant, otherwise the microclimate around the sleeved plant can quickly accumulate damaging levels of ethylene (Figure 1). Sleeve plants just before they are being shipped and remove the sleeves as soon as possible. Open carts are a great way to transport your finished crop because it is an efficient way to move plants without damage, and it allows for air flow around the plants within the truck (Figure 2). Use electric pull-carts to transport the plants from the production area to the loading dock. If you put shrink wrap around the carts to keep plants in place, this can also create a microclimate with high relative humidity and high ethylene levels. Minimize the time that plants are on these carts and make sure that the plants are held in place by the wrap, but not completely sealed in. Deadheading flowers and removing dying leaves makes the crop more attractive, but it also removes potential sources of ethylene. Dying flowers and leaves produce ethylene, and botrytis and other fungi that degrade dying plant material also produce their own ethylene.

 

Figure 1. Perforated sleeves allow ethylene to escape from packaging. This is especially important for ethylene sensitive crops like petunias.

Figure 1. Perforated sleeves allow ethylene to escape from packaging. This is especially important for ethylene sensitive crops like petunias.

 

Figure 2. Open carts are an ideal way to ship ethylene sensitive crops because it allows air movement around the plants and protects them from damage. Always use electric pull-carts to transport the plants to the shipping area. If carts are shrink wrapped (right photo), make sure the plastic is holding them in pace but not completely sealing them in.

Figure 2. Open carts are an ideal way to ship ethylene sensitive crops because it allows air movement around the plants and protects them from damage. Always use electric pull-carts to transport the plants to the shipping area. If carts are shrink wrapped (right photo), make sure the plastic is holding them in pace but not completely sealing them in.

 

 

Package and sort orders in a well ventilated loading dock area that is free of sources of ethylene. If possible, load trucks in the early morning hours when it is cooler. Plants not only produce more ethylene at higher temperatures, but they are more sensitive to ethylene damage at high temperatures. This means that lower amounts of ethylene are needed to cause damage at high temperatures. Do not let truck engines idle while loading and do not use propane or gas powered forklifts inside the trucks or enclosed areas where plants are being held. The combustion of propane, natural gas or gasoline can produce ethylene. Ethylene from external or non-plant sources can cause direct damage to plants, but it also causes the exposed plants to increase their own ethylene production.

Ethylene is such a problem during shipping, because it is a gas. If any plants in your shipment are producing ethylene it is released into the air and can move throughout the truck. If plants are sealed in a truck for 1 to 3 days (or more) levels of ethylene in the ppm range can accumulate and cause significant damage to the entire shipment.

 

Dr. Michelle L. Jones
D.C. Kiplinger Chair in Floriculture
Associate Professor
The Ohio State University
Department of Horticulture and Crop Science
330-263-3885
Jones.1968@osu.edu
http://oardc.osu.edu/floriculture/
http://oardc.osu.edu/joneslab/

Preventing ethylene damage in the production greenhouse: using indicator plants

How do you determine if you have ethylene contamination in your greenhouse?

The best way you can determine if you have ethylene contamination in your greenhouse is to carefully monitor plants that are sensitive to ethylene for symptoms of damage. This includes accelerated flower wilting or leaf yellowing, shedding of leaves or petals, and abnormal or stunted growth. If you suspect that you may have an ethylene problem, you can place indicator plants in the greenhouse. The best indicator plant is tomato, which will show epinasty or downward bending of the leaves when exposed to very low concentrations of ethylene (Figure 1). Place young tomato plants near heaters or any source you suspect may be producing ethylene (Figure 2). Tomatoes will be one of the most ethylene sensitive plants in your greenhouse, so if you observe symptoms of epinasty you should have time to remediate the problem and prevent permanent damage to your crops. Juvenile plants (before flowering) are more sensitive to ethylene than mature flowering plants, and they will show symptoms of ethylene damage at lower concentrations of ethylene. Once your indicator tomato plants flower you should replace them with younger seedlings.

 

Figure 8 (2)

Figure 1. Epinasty in tomato plants. Tomato plants exposed to ethylene exhibit downward curvature of the leaves (top photo- plant on the right and bottom photo).

Figure 1. Epinasty in tomato plants. Tomato plants exposed to ethylene exhibit downward curvature of the leaves (top photo- plant on the right and bottom photo).

 

 

FIgure 2. Place indicator plants near a heater or any other potential source of ethylene.

FIgure 2. Place indicator plants near a heater or any other potential source of ethylene.

 

 

If you see epinasty in your indicator plants, you must immediately identify the source of ethylene and remove it or turn it off (i.e. heaters). The greenhouse can then be ventilated to remove the ethylene gas. Ethylene damage may easily be confused with other types of stress that cause similar symptoms. If you suspect you may have an ethylene problem or you would just like more information please feel free to contact me. We can use an instrument called a gas chromatograph to measure air samples and determine if ethylene levels in your facility are high.

Inquiries about ethylene damage have increased considerably in the last few years. Losses due to ethylene contamination can be devastating to both small and large greenhouse producers. If you are aware of the potential sources of ethylene gas in the greenhouse and you are able to recognize the symptoms of ethylene damage, crop losses can be prevented. Indicator plants are the best way to diagnose potential problems.

 

Dr. Michelle L. Jones
D.C. Kiplinger Chair in Floriculture
Associate Professor
The Ohio State University
Department of Horticulture and Crop Science

330-263-3885
Jones.1968@osu.edu

http://oardc.osu.edu/joneslab/

http://osu.floriculture.edu

Preventing ethylene damage in the production greenhouse: Proper heater installation and maintenance and electric carts!!

How to prevent ethylene damage

The proper maintenance and installation of heating units is the best way to prevent ethylene damage in the greenhouse. Regular maintenance should include inspection of heat exchangers, exhaust vent stacks and fuel lines. Leaks in gas lines can be identified by looking for bubbles following the application of soapy water. The heater should have a stable flame with a blue cone center. A yellow or orange flame indicates there is not enough oxygen for complete combustion of the fuel. Incomplete combustion can result in the production of harmful gases including ethylene and carbon monoxide. An outside air supply duct may be needed to provide enough oxygen for complete combustion, and proper air exchanges help remove contaminants like ethylene gas from the greenhouse.

Indirect fired heaters must be vented outside of the greenhouse so that the byproducts of combustion are not released directly into the growing environment. A few considerations for non-power vented heaters include the height of the exhaust stack and placement near vents that are bringing air into the greenhouse (Figure 1). Greenhouses should follow the 2:3:10 rule if you are using passive ventilation from a vertical chimney stack. The top of the chimney stack must be at least 2 feet above the ridge of the roof. If the chimney placement is on the edge of the roof then the top of the stack must be at least 3 feet above the roof surface. This chimney top must be high enough above the roof of the greenhouse such that at it is at least 10 feet across to the nearest roof surface. In other words, a horizontal line drawn from the top of the chimney must run at least 10 feet before it touches a roof surface. Concurrent heating and venting for relative humidity management or high wind velocities can create a negative pressure in the greenhouse that results in a downdraft that sucks the exhaust gases back into the greenhouse. Power-vented heaters use a blower to actively exhaust the flue gases and this prevents problems with back drafts. These vents can run horizontally out the wall of the greenhouse and should be at least 3 feet from any air intakes.

Figure 7 (2)

IMG_2037

IMG_2034

 

 
Figure 1. Improper chimney heights and heaters that are not properly vented result in combustion byproducts, including ethylene, coming back into the greenhouse.

 

Unvented burners have been used by growers to enrich the growing environment with CO2, but all combustion byproducts including ethylene are also released into the greenhouse. Recently, higher capacity direct-fired heaters have become available for heating production environments. These heaters are not vented and all products of combustion go into the greenhouse for heating. If these heaters are installed according to the manufacturer’s instructions and have proper air exchange to reduce relative humidity and insure efficient combustion, they can be run without producing ethylene. For a little piece of mind with any heater, vented or non vented, grow a few tomatoes near them as indicator plants.

Avoid the use of any equipment or vehicles that use combustion engines. Use only electric carts to move plants within the greenhouse. If you must use propane powered forklifts in loading docks make sure these areas are well ventilated to remove any ethylene that might be generated.

 

Dr. Michelle L. Jones
D.C. Kiplinger Chair in Floriculture
Associate Professor
The Ohio State University
Department of Horticulture and Crop Science
330-263-3885
Jones.1968@osu.edu

Preventing ethylene damage in the production greenhouse: symptoms of ethylene damage

The severity of ethylene damage depends on the sensitivity of the plant species to ethylene, the concentration of ethylene, the amount of time the plant is exposed, and the temperature. High temperature stress causes plants to produce more ethylene, but plants are also more sensitive to damage from ethylene contamination at higher temperatures. In general, young flower buds are less sensitive to ethylene damage than open flowers, and leaves are less sensitive than flowers. Figure 1 shows how the dose of ethylene (concentration over time) affects impatiens.

 

Figure 1. Ethylene dose response in impatiens. The severity of ethylene damage is determined by the sensitivity of the specific crop but also the concentration of ethylene and the time that the plant is exposed. Impatiens are considered to be highly sensitive to ethylene. After one day of exposure to 2 ppm ethylene most open flowers are shed. After two days all of the open flowers have been lost and buds also begin to abscise. After 3 days the plants do not have any flowers or buds.

Figure 1. Ethylene dose response in impatiens. The severity of ethylene damage is determined by the sensitivity of the specific crop but also the concentration of ethylene and the time that the plant is exposed. Impatiens are considered to be highly sensitive to ethylene. After one day of exposure to 2 ppm ethylene most open flowers are shed. After two days all of the open flowers have been lost and buds also begin to
abscise. After 3 days the plants do not have any flowers or buds.

 

In a greenhouse production environment plants may be exposed to lower concentrations (25 to 200 ppb; parts per billion) of ethylene over weeks or even months during the colder times of the year. This type of chronic ethylene exposure results in stunted or malformed growth, flowers that do not initiate, and flower bud abortion. If grown to flowering under these conditions, the flowers become smaller and show accelerated death. Leaves start to prematurely yellow (i.e. chlorosis) and eventually they will become brown and dry (i.e. necrotic). This type of ethylene damage can be hard to diagnosis, because similar symptoms may result from nutrient or pathogen disorders. In many instances where constant low levels of ethylene are present in the production environment, you may first observe damage on ethylene sensitive crops grown in hanging baskets (like geraniums). This is because ethylene is lighter than air and it will accumulate to higher concentrations up in the peak of the greenhouse.

If exposed to higher levels of ethylene, in the ppm (parts per million) range, ethylene damage occurs much more quickly. At 1 ppm, ethylene is considered to have full biological activity and most plants will show some signs of damage within hours or a few days. This damage is much easier to attribute to ethylene. In these instances it is likely that plants will be growing well and you will come in one morning to find that all the open flowers on your geranium baskets have been shed. Symptoms of acute ethylene damage include shedding or shattering of leaves, buds or petals, rapid flower aging (i.e. senescence) and wilting or leaf yellowing (Figure 2). A classic symptom of ethylene damage is epinasty (Figure 3). This is the characteristic downward growth of the leaf petiole. Plants look like they are experiencing drought stress, but they are well hydrated and fully turgid. While many different plants show epinasty, tomatoes consistently show the most severe epinasty at the lowest concentrations of ethylene.

 

Figure 2. Symptoms of exposure to 3 ppm ethylene for 2 days. Portulaca retain most of their buds but all open flowers wilt. The most dramatic symptom of ethylene damage in portulaca is the large loss of leaves.

Figure 2. Symptoms of exposure to 3 ppm ethylene for 2 days. Portulaca retain most of their buds but all open flowers wilt. The most dramatic symptom of ethylene damage in portulaca is the large loss of leaves.

 

Figure 3. When exposed to ethylene tomato plants exhibit epinasty or the downward curvature of the leaves.

Figure 3. When exposed to ethylene tomato plants exhibit epinasty or the downward curvature of the leaves.

 

Will ethylene damaged plants recover?

This is a hard question to answer. In most instances ethylene damage will not kill your crop, but it will often impact the marketability of the crop by delaying flowering or by removing all open flowers. Ethylene damage at the young seedling stage can result in plant death and entire crops may need to be replanted. The geranium hanging basket shown in Figure 3 was produced in a greenhouse that contained 800 ppb ethylene over a period of multiple weeks (or longer). Extensive damage like this essentially results in a crop that is not saleable. When removed from the ethylene environment, new growth resumed on these baskets but flowering was delayed by over one month (Figure 3). Most plants with moderate damage will resume normal vegetative growth and flowering within 1 to 2 weeks. In contrast, plants like tulips and Easter lilies, that flower only once, will not recover when buds and open flowers have been damaged by ethylene. Plants experiencing epinasty will recover quite quickly and these crops are the most likely to remain of marketable quality.

 

Figure 6 (1)

Figure 4. Geranium hanging basket (top) produced in a greenhouse that contained ethylene contamination at 800 ppb as determined by a gas chromatograph. This crop suffered extreme ethylene damage. All flowers prematurely senesced and leaves yellowed and eventually became brown and necrotic. Plants resumed vegetative growth after removal from the ethylene (far right plant in the bottom photo), but when compared to plants that were produced in a non contaminated environment (left plant in the bottom photo) they are very significantly delayed. One month after removal from the ethylene contaminated greenhouse these geraniums still did not have any flower buds.

Figure 4. Geranium hanging basket (top) produced in a greenhouse that contained ethylene contamination at 800 ppb as determined by a gas chromatograph. This crop suffered extreme ethylene damage. All flowers prematurely senesced and leaves yellowed and eventually became brown and necrotic. Plants resumed vegetative growth after removal from the ethylene (far right plant in the bottom photo), but when compared to plants that were produced in a non contaminated environment (left plant in the bottom photo) they are very significantly delayed. One month after removal from the ethylene contaminated greenhouse these geraniums still did not have any flower buds.

 

 

 

Dr. Michelle L. Jones

D.C. Kiplinger Chair in Floriculture

Associate Professor

The Ohio State University

Department of Horticulture and Crop Science

330-263-3885

Jones.1968@osu.edu