Raise your hand if you have interest in increasing the shelf life of your crops! Growers of any kind can relate to the problem of shrinkage, flower abortion, and overall quality degradation during the critical period between crop finishing and sale. This article will dive into effective cultural and chemical strategies to aid in extending the shelf life of the crops you worked so hard to produce.
Temperature
Researchers have shown us that average daily temperature (ADT) is the best predictor of determining the rate of plant maturity. Using your thermostat as a tool to slow down or speed up crop growth takes experience and knowledge because not all plants will tolerate the same temperature thresholds. The minimum base temperature in which greenhouse grown crops stop developing falls within a wide range. There are numerous plants that will not tolerate cool production temperatures over extended periods, including ageratum, angelonia, browallia, celosia, gerbera, gomphrena, hibiscus, pentas, portulaca, vinca and zinnia (Lopez & Runkle). For this list of crops, growers should strive to achieve, at minimum, 60-degree F night and day temperatures. Most other crops will allow for night temperatures in the 50’s with cool days. Cooler temperatures, however, increase relative humidity and thus, leaf surface condensation, leading to Botrytis. It is recommended to treat preventatively with a fungicide like Affirm, Astun, Mural, Pageant Intrinsic, Palladium, Medallion, Postiva, and Triathlon BA or Cease. Reach out GGSPro to help determine a bloom safe option and the appropirate rates for your specific situation.
For species that tolerate cold temperatures, outdoor production can produce superior plants with exposure to higher light, wind, and cooler temperatures, which will all slow down plant development and help with hardening off. These crops will do well on gravel pads, ground cover fabric outdoors, or in cold frame structures with roll up sides that can protect from heavy rains and random freezes. A week of cold temperatures in the low 40’s is sufficient for hardening off. If needed, Pageant Intrinsic, made by BASF, has been shown to increase cold tolerance by a few degrees for several plant species. Apply 2-7 days before the plants experience frost or freeze to maximize its cold tolerance benefits.
Figure 1: Petunia growth and flowering is delayed in colder temperatures. (Source: Neil Mattson, Cornell University)
Research has shown that the majority of stem elongation or “stretch” generally occurs in the first 3 hours of the morning with the onset of daybreak when plants become photosynthetically active. Growers can help reduce plant stretch by altering the temperature during daybreak and a few subsequent hours to be 5 degrees below that of the night temperature set point. Normal temperature settings can then be restored for the rest of the day afterwards. This allows for stretching to be significantly reduced with much less impact on the average daily temperature. This “DIP” technique can reduce or eliminate the need for growth regulators on many crops, however, PGR’s still have a vital function in a grower’s chemical cabinet.
Plant Growth Regulators (PGRs)
Plant Growth Regulators (PGRs) can make your crop more profitable by allowing a higher crop density and increasing shelf life. There is a wide array of PGR options available with different advantages such as minimizing internode elongation, promoting growth of less vigorous plants, preventing flower development, and increasing lateral branching. How do you decide which one to use? Rate, application method, environmental conditions, time of year, and plant development stage are all considered when choosing the appropriate PGR, application method, and rate. As a rule of thumb, PGR drench applications hold plants longer and have less impact on bloom timing and bloom size when compared to foliar applications. Soilless media with pine bark will require higher PGR drench rates than other mixes, all other factors being equal. Paclobutrazol is widely used as the drench treatment of choice, especially for growers new to PGRs, because it can be used on so many ornamental crops and rates are well established. Bonzi, Piccolo, Pac O, and Paclo Pro all contain this active ingredient. These products are typically either applied as a single, high dose drench to provide longer control, or more frequently, at lower concentrations to provide temporary control of the plant. It can also be applied as a foliar spray.
Figure 2. Leaving a “check” (front middle) plant untreated to ensure PGR applications were efficacious. (Source: Grower Talks Magazine, 2024)
Additionally, Alesco is a unique and inexpensive product applied as a foliar spray at 3/4 tsp per gallon (or 12.8 FL oz per 100 gal; 1 container in 50 gal of water treats approximately 1 acre) 1-2 days before shipping, that can add up to three weeks of shelf life by reducing petal shatter, bud abortion, and extending flower longevity. This product is especially helpful to plants which are sensitive to ethylene damage, like geranium, impatiens, pansy, petunia, dahlia, dianthus, rose, phlox, and viola.
Figure 3. Chrysal’s Alesco® sprayed 2 days before shipping protected plants during 3 days of simulated shipping stress from the negative effects of ethylene. (Source: Chrysal)
Note, not all products are registered in all states. Some pesticides are restricted use in some states or regions and not others. It is the responsibility of the applicator to read and follow all label directions, remembering that labels may change. Other products may be safe and effective. Rates, application methods, and edible status are detailed in our GGSPro Insecticide & Fungicide Guides. Griffin also offers the 5th Edition GGSPro Technical Reference Guide in both English and now Spanish versions. This valuable resource outlines a wide range of pest control options and information on pollinator safety, BCA’s, scouting, weed management, plant lighting, nutrition, water quality and more!
Temperature
Researchers have shown us that average daily temperature (ADT) is the best predictor of determining the rate of plant maturity. Using your thermostat as a tool to slow down or speed up crop growth takes experience and knowledge because not all plants will tolerate the same temperature thresholds. The minimum base temperature in which greenhouse grown crops stop developing falls within a wide range. There are numerous plants that will not tolerate cool production temperatures over extended periods, including ageratum, angelonia, browallia, celosia, gerbera, gomphrena, hibiscus, pentas, portulaca, vinca and zinnia (Lopez & Runkle). For this list of crops, growers should strive to achieve, at minimum, 60-degree F night and day temperatures. Most other crops will allow for night temperatures in the 50’s with cool days. Cooler temperatures, however, increase relative humidity and thus, leaf surface condensation, leading to Botrytis. It is recommended to treat preventatively with a fungicide like Affirm, Astun, Mural, Pageant Intrinsic, Palladium, Medallion, Postiva, and Triathlon BA or Cease. Reach out GGSPro to help determine a bloom safe option and the appropirate rates for your specific situation.
For species that tolerate cold temperatures, outdoor production can produce superior plants with exposure to higher light, wind, and cooler temperatures, which will all slow down plant development and help with hardening off. These crops will do well on gravel pads, ground cover fabric outdoors, or in cold frame structures with roll up sides that can protect from heavy rains and random freezes. A week of cold temperatures in the low 40’s is sufficient for hardening off. If needed, Pageant Intrinsic, made by BASF, has been shown to increase cold tolerance by a few degrees for several plant species. Apply 2-7 days before the plants experience frost or freeze to maximize its cold tolerance benefits.
Figure 1: Petunia growth and flowering is delayed in colder temperatures. (Source: Neil Mattson, Cornell University)
Research has shown that the majority of stem elongation or “stretch” generally occurs in the first 3 hours of the morning with the onset of daybreak when plants become photosynthetically active. Growers can help reduce plant stretch by altering the temperature during daybreak and a few subsequent hours to be 5 degrees below that of the night temperature set point. Normal temperature settings can then be restored for the rest of the day afterwards. This allows for stretching to be significantly reduced with much less impact on the average daily temperature. This “DIP” technique can reduce or eliminate the need for growth regulators on many crops, however, PGR’s still have a vital function in a grower’s chemical cabinet.
Plant Growth Regulators (PGRs)
Plant Growth Regulators (PGRs) can make your crop more profitable by allowing a higher crop density and increasing shelf life. There is a wide array of PGR options available with different advantages such as minimizing internode elongation, promoting growth of less vigorous plants, preventing flower development, and increasing lateral branching. How do you decide which one to use? Rate, application method, environmental conditions, time of year, and plant development stage are all considered when choosing the appropriate PGR, application method, and rate. As a rule of thumb, PGR drench applications hold plants longer and have less impact on bloom timing and bloom size when compared to foliar applications. Soilless media with pine bark will require higher PGR drench rates than other mixes, all other factors being equal. Paclobutrazol is widely used as the drench treatment of choice, especially for growers new to PGRs, because it can be used on so many ornamental crops and rates are well established. Bonzi, Piccolo, Pac O, and Paclo Pro all contain this active ingredient. These products are typically either applied as a single, high dose drench to provide longer control, or more frequently, at lower concentrations to provide temporary control of the plant. It can also be applied as a foliar spray.
Figure 2. Leaving a “check” (front middle) plant untreated to ensure PGR applications were efficacious. (Source: Grower Talks Magazine, 2024)
Additionally, Alesco is a unique and inexpensive product applied as a foliar spray at 3/4 tsp per gallon (or 12.8 FL oz per 100 gal; 1 container in 50 gal of water treats approximately 1 acre) 1-2 days before shipping, that can add up to three weeks of shelf life by reducing petal shatter, bud abortion, and extending flower longevity. This product is especially helpful to plants which are sensitive to ethylene damage, like geranium, impatiens, pansy, petunia, dahlia, dianthus, rose, phlox, and viola.
Figure 3. Chrysal’s Alesco® sprayed 2 days before shipping protected plants during 3 days of simulated shipping stress from the negative effects of ethylene. (Source: Chrysal)
| Item Name | Active Ingredient | Item Number |
|---|---|---|
| Bonzi | Paclobutrazol | 70-1260 |
| Pac O | Paclobutrazol | 73-1845 |
| Paclo Pro | Paclobutrazol | 73-1830 |
| Piccolo | Paclobutrazol | 73-1915 |
| Alesco | Silver Nitrate | 73-1160 |
| Affirm | Polyoxin D zinc salt | 71-1131 |
| Astun | Isofetamid | 71-1190 |
| Cease | Bacillus subtilis QST 713 strain | 71-13301 |
| Medallion | Fludioxonil | 71-16502 |
| Mural | Azoxystrobin & Solatenol | 71-1690 |
| Pageant Intrinsic WG | Boscalid & Pyraclostrobin | 71-2683 |
| Palladium | Cyprodinil & Fludioxonil | 71-2685 |
| Postiva | Pydiflumetofen & Difenoconazole | 71-2400 |
| Triathlon BA | Bacillus amyloliquefaciens strain D747 | 71-3040 |
Note, not all products are registered in all states. Some pesticides are restricted use in some states or regions and not others. It is the responsibility of the applicator to read and follow all label directions, remembering that labels may change. Other products may be safe and effective. Rates, application methods, and edible status are detailed in our GGSPro Insecticide & Fungicide Guides. Griffin also offers the 5th Edition GGSPro Technical Reference Guide in both English and now Spanish versions. This valuable resource outlines a wide range of pest control options and information on pollinator safety, BCA’s, scouting, weed management, plant lighting, nutrition, water quality and more!