Coleus as Cut Foliage

This project was supported by the ASCFG Research Foundation.  The authors would like to thank Diane Mays and Tina Krug for assisting with growing the coleus and the postharvest studies.

How many of us remember coleus in our grandmother’s garden?  Every fall grandmother would take cutting from the plants, usually small-leaved forms with red on the foliage, and overwinter them in a jar of water on the windowsill.  The next spring the rooted cuttings would be planted in a pot and placed outdoors to start the cycle over again.  Today, the coleus has been reborn as a major cutting-propagated bedding plant.  The many types lurking in various gardens have been rediscovered and supplemented with hundreds of new cultivars from breeders.  The result is a wonderful array of colors, leaf shapes and sizes and growth habits. Specialty cut flower growers, constantly searching for new and different cuts to offer their customers, have long eyed coleus.  It offers a great diversity of color, leaf sizes, and leaf shapes.  Coleus has the advantage of not only serving as a filler foliage but also adds color to the bouquets or arrangements.  Trials by growers indicate that some coleus cultivars have problems with hydrating initially, but generally have a long enough vase life.  In addition, while there are hundreds of coleus cultivars available, many are low growing, slow growing or heavily branched  making them unsuitable for cut flower production.  However, several cultivars have long stems, are relatively rapidly growing, and have attractive foliage colors.  The goal of our study was to determine which cultivars would make acceptable cut foliages.  

Cultivars

Oklahoma State University grew 25 cultivars and North Carolina State University grew 13 cultivars.  All were sun coleus that produce the best colors in full sun outdoors.  However, they could be grown with part shade outdoors.  The North Carolina cultivars  selected were ones that have been grown for landscape use in the Raleigh area for several years.  One of the cultivars we tested was actually Perilla, a genus closely related to coleus, which is in the genus Solenostemon.  Perilla is often mistaken for coleus but is available in only a few colors, while coleus colors seem to span the rainbow.  Perilla is grown and used in a similar fashion to coleus.  


Production—OSU: We grew 25 cultivars in 6-inch pots, using BM1 media, with one plant per pot.  Pots were planted on August 30 using rooted plugs and plants were pinched the same day.  Plants were grown in a polycarbonate-covered greenhouse set at 62F night temperature/75F day with automatic drip tube irrigation.  Plants were fertigated with 150 ppm nitrogen from 21-5-20.  The stems were harvested on December 11, 2006.  We only recorded the length of stems longer than 12 inches.

Production—NCSU: We grew 13 cultivars in heavy plastic flats (14 x 20.5 inches, 4 inches deep) with eight plants per flat.  Flats were planted on June 16 using rooted plugs and plants were pinched the same day.  Plants were grown in a plastic-covered greenhouse set at 65F night temperature/75F day with automatic drip tube irrigation.  Plants were fertigated with 150 ppm nitrogen from 20-10-20.  Twelve of the cultivars were harvested on July 25 and 26.  The cultivar ‘Glennis’ was much slower growing than the other cultivars and was harvested on October 2.  We only recorded the length of stems longer than 12 inches.

Postharvest—OSU: After harvest the stems were immediately placed in water, carried to the headhouse and placed in Floralife overnight.  Stems were then packed into floral boxes and shipped overnight to NSCU.  After receipt, stems were unpacked and placed in vases with water.

Postharvest—NCSU: After harvest the stems were recut to 12 inches and placed in the following treatments:
1.    Directly into vases with tap water.
2.    Directly into vases with tap plus Chrysal Professional #2.
3.    Directly into vases with Floralife Professional.
4.    Placed in buckets of tap water for 7 days at 68F, then in vases with tap water.
5.    Placed in buckets of tap water for 7 days at 41F, then in vases with tap water.
6.    Placed in buckets of tap water overnight, then placed dry in floral boxes for 24 hours,  after which they were recut and placed in vases               with tap water.
7.    Placed in buckets of tap water and treated with Ethylbloc (1-MCP) for 4 hours, then stored for 7 days at 68F (for only three cultivars)

After treatment, stems were placed in vases at 68+4F under approximately 200 fc light for 12 hrs/day.  Stems were terminated primarily due to wilting; stems wilted either immediately after harvest, or after being stored, and never rehydrated.  

Production results—OSU:  Plants took much longer to produce harvestable stems, over 3 months, in the cool fall and early winter conditions at OSU, than at NC State in the summer.  This is not surprising considering that coleus are known to grow best in warm weather and certainly, the best time to produce them as cuts would be from spring to early fall.  In addition, since coleus are facultative short-day plants, the plants tended to flower quickly, reducing stem length.  We would expect longer stems and more of them in the summer.  ‘Oompah’ produced the longest average stem length, 20 inches, but ‘Oxblood’, ‘Purpleosity’,  ‘Religious Rudibaga’, ‘Roaring Fire’, ‘Swinging Linda’ and ‘Yin and Yang’ produced stems at least 18 inches long (Table 1).   The stem length for the rest of the cultivars ranged from 13.2 to 17.8 inches long.  No pest problems occurred.
    
Plants produced 2.2 to 7.6 stems per plant (Table 1).  Only stems at least 12 inches long were harvested.  The cultivars that produced the greatest number of long stems were ‘Swinging Linda’ and ‘Yin and Yang’.

Production results—NCSU:  The plants were easy to grow in the deep flats.  Using automatic irrigation we had relatively few problems, except for mealybugs (coleus is one of their favorites).  While we did not use netting, the crop could have benefited from it. The stems tended to be weak and by the time they reached harvestable length, the stems started to lean over and were easily broken. The coleus had fairly brittle stems, which tended to break during harvest if we were not careful.  
    
Most of the cultivars grew fast, producing 18-inch or longer stems in 40 days from planting a rooted cutting in the summer (Table 2).  ‘Appaloosa’ produced the longest average stem length, 23 inches, but many individual stems were much longer.  The shortest cultivar was ‘Glennis’, which was an exceptionally slow grower.  We did not harvest it at the same time as the other cultivars because none of the stems was over 12 inches long at the time.  However, ‘Glennis’ eventually produced stems averaging 20 inches.  The stem length for the rest of the cultivars ranged from 17 to 22 inches long.  

Postharvest—OSU:  All stems wilted during harvest.  Most rehydrated after placement in the Floralife solution, except for ‘Antique’, ‘Blusher’,  ‘Mississippi Summer’, ‘Purpleosity’  and  ‘Saturn’ (Table 1).  All of these cultivars were still wilted after 12 hours in the Floralife solution.  In addition, some of the cultivars that rehydrated after harvest showed some wilting 12 hours later.  After being shipped dry to NC State, none of the stems rehydrated.

Postharvest—NCSU:  The use of floral preservatives decreased the vase life of most cultivars compared with tap water only (Table 3).  Even the treatments where the floral preservatives produced a longer vase life, the effect was only marginal.  In those treatments most stems did not rehydrate but enough few stems rehydrated to increase the average vase life.  Many stems of most cultivars rooted when placed in tap water; however, few stems rooted in the floral preservatives (Table 4).  Those stems that did root in the preservative, generally did so further up the stem as the end of the stem decayed.
   

Stems did not tolerate 41F cold storage at all and most were either dead at the end of storage or never rehydrated (Table 3).  We tested storing the stems in buckets at 68F to see if we could start the rooting process while storing the stems in bulk.  The stems could then be sold by the grower and would last a long time for the customer.  Great theory.   Too bad it didn’t  work.  Surprisingly, stems of most cultivars did not tolerate being stored in buckets of tap water at 68F either.  However, stems placed directly in vases of tap water at the same temperature often had a long vase life and rooted.  While the buckets of stems were stored in a lighted cooler, the amount of light reaching each stem was a lot less than the amount of light reaching each stem placed directly into the vase.  If we had tried to store the cut stems in clear buckets or large vases we might have had different results.  Ethylbloc (MCP) treatment had no apparent effect on stored cut stems; however, we tested it on only three cultivars. 

Coleus stems did not tolerate dry storage, even though the stems were held dry  for only 24 hours (Table 3).  The exception was ‘Black Star’  which was one of the durable cultivars, overall.

Cultivars

Many of the cultivars at both OSU and NCSU produced acceptable results.  The most productive cultivars at OSU were ‘Swinging Linda’ and ‘Yin and Yang’,  both of which also rehydrated after harvest and did not wilt later.  At NCSU the best overall cultivar was ‘Freckles’, as it produced over 18 stems/plant, which averaged 20 inches long, and lasted over 19 days in water.  ‘Black Star’ and ‘Magilla’ perilla had the longest vase life and were the most durable but were not as productive as many of the other cultivars.  ‘Appaloosa’ and ‘Saturn’ produced a lot of long stems but the postharvest life as not as good.

We would be remiss if we didn’t  make a comment about coleus names.  With the proliferation of cultivars, especially from small producers, folks have been very creative with the names.  ‘Dappled Apple and ‘Dipt in Wine’ are delectable, not a word we normally get to use with ornamentals.  While ‘Green Meanie’ and ‘Religious Rudibaga’ don’t tell us much about the color, they definitely are fun to say and will make great conversations with your customers when you sell the stems.   ‘Smallwoods Drive’ might be a bit pedestrian but ‘Swinging Linda’ sure hits the mark.

Conclusion

Too much potential to give up on.  The colors were great and the plants easy to grow and productive.  The best time to grow coleus is during warm weather and long days from spring to fall.  Winter production would slow growth and the short days would induce flowering, limiting stem length.  

The main problem continues to be postharvest.  Most stems wilt very easily and do not rehydrate well.  Lynn Byczynski recently published an article in Growing for Market [Could Coleus become a popular cut?, 2006, 15(12):6-7] detailing her trials with cut coleus.  She came to the same conclusions as we did: coleus has serious postharvest issues but is worth the effort.  As with our work she noted that some cut coleus stems wilted easily, while others didn’t and that many stems rooted within a week.
    
The key to success may be to rapidly harvest the stems, early in morning, directly into buckets of water.  We harvested and measured our stems, resulting in a long harvest time, which allowed the stems to dehydrate.  We had too many stems to harvest all at once, and so we harvested more than one day.  We noticed that the stems harvested on cool, cloudy days were more likely to rehydrate.  Another possibility is that the plants were too soft from being grown in a greenhouse with constant moisture.  Postharvest performance might have been better if the plants had been grown outdoors (which would shorten stems, unfortunately) or had been grown drier (which would also shorten stems).  Regardless, we hope growers will continue to experiment with this interesting group of plants and let us know what works for them.

Table 1.  Stem number and length of 25 cultivars harvested at Oklahoma State University on December 11.  Plants were planted August 30.

 Cultivar# of StemsStem LengthRehydratedWilted
 per pot(inches)after harvestafter 12 hours
 Amazon 3.415.3YesNone
 Antique 5.616.5NoAll
 Aurora 4.514.6YesNone
 Blusher 4.215.1NoAll
 Copper Glow 2.213.5YesNone
 Dappled Apple 6.516.9YesSome
 Dawn6.217.8YesSome
 Dipt in Wine3.616.4YesNone
 Fusion3.413.2YesSome
Gold Bound6.216.5YesAll
 Green Meanie7.616.3YesSome
 Grape Expectations 7.016.2YesNone
 Lavender Lace 5.416.0YesNone
 Mississippi Summer 4.617.1NoAll
 Oompah5.020.0YesSome
 Oxblood2.618.5YesNone
 Purpleosity5.219.3NoAll
 Religious Rudibaga3.418.3YesSome
 Roaring Fire5.618.5YesNone
 Saturn3.615.8NoAll
 Smallwoods Drive2.813.6YesNone
 Swinging Linda7.218.0YesNone
 The Line3.014.1Yes Some
 Trailing Queen2.414.4YesSome
 Yin and Yang7.418.8YesNone
 Significance0.0001
 LSD 0.052.3


Table 2
.  Stem number and length of 13 cultivars harvested on July 25 and 26.  Glennis was a slow growing cultivar and was not ready for harvest with the other cultivars and was harvested October 2.  All cultivars were planted June 16.

 CultivarStemsStemsStems
 per crateper plantLength
 (no.)(no.)(inches)
Coleus   
Appaloosa14017.523 a
Black Star8911.121 b
Defiance11414.316 g
Freckles14918.622 a
Giant Fantasy9411.818 ef
Glennis13917.420 c
Kingwood Torch9311.618 de
Lord Voldemort12115.121 b
Pineapple Prince13217.317 f
Pineapple Red10613.319 cd
Rustic Orange9912.418 ef
Saturn15018.821 b
Perilla   
‘Magilla’10813.522 a
Significance0.0001

 Means followed by the same letter are not significantly different.

Table 3.  Vase life of 13 cultivars of coleus and perilla.  Stems were harvested, sorted, recut and placed directly into 1) tap water, 2) Chrysal Professional #2, or 3) Floralife Professional, stored in buckets of tap water for 7 days at 4) 68oF or 5) 41oF, 6) placed in buckets of tap water overnight, then placed dry in floral boxes for 24 hours, or 7) placed in buckets of tap water and treated with Ethylbloc (1-MCP) for 4 hours, then stored for 7 days at 68oF (for only three cultivars).   

  Vase Solution Vase Solution Vase SolutionStored in tap water at:Stored in tap water at:Hydrated thenHydrated then
 Tap waterChrysalFloralife6841overnight dryEthylbloc
Coleus       
Appaloosa8.7a4.5b0.1c7.8a01.1bc
Black Star23.5a23.2a12.6b19.0a010.0a19.7a
Defiance6.9a4.4b0.3c7.5a04.2b
Freckles19.7a19.0a9.6bc13.0b04.2b
Giant Fantasy14.0a14.0a4.4c8.9b00.9bc
Glennis1.0c3.8bc3.4c13.0a00c
Kingwood Torch14.0a10.8b3.1d8.1c04.5b
Lord Voldemort6.3b1.6c9.0a00c9.0a
Pineapple Red9.2a5.5b0.2d7.7ab00c
Pineapple Prince1.0d5.8b1.0d10.3a00c
Rustic Orange6.8b0.2d0d14.0a01.4bc
Saturn1.0d6.9b1.0d9.0a00c
Perilla       
‘Magilla’25.0a23.8a4.6b25.0a05.0b21.9a
Significance0.00010.00010.00010.0001NS0.00010.0001

  Means followed by the same letter are not significantly different.

Table 4.  Status of the majority of stems in each treatment at the time of termination.  In most of the treatments, some of the stems were terminated for reasons other than indicated.  “DNR” refers to “does not rehydrate”.  Stems were harvested, sorted, recut and placed directly into 1) tap water, 2) Chrysal Professional #2, or 3) Floralife Professional, stored in buckets of tap water for 7 days at 4) 68oF or 5) 41oF, 6) placed in buckets of tap water overnight, then placed dry in floral boxes for 24 hours, or 7) placed in buckets of tap water and treated with Ethylbloc (1-MCP) for 4 hours, then stored for 7 days at 68oF (for only three cultivars).

  Vase Solution Vase Solution Vase SolutionStored in tap water at:Stored in tap water at:Hydrated thenHydrated then
 Tap waterChrysalFloralife6841overnight dryEthylbloc
Coleus       
AppaloosarootedwiltedDNRDNRDNRDNR
Black StarrootedwiltedwiltedrootedDNRwiltedrooted
DefiancerootedDNRDNRDNRDNRDNR
FrecklesrootedwiltedwiltedDNRDNRDNR
Giant FantasyrootedrootedDNRDNRDNRDNR
GlennisDNRDNRDNRrootedDNRDNR
Kingwood TorchrootedrootedDNRDNRDNRDNR
Lord VoldemortrootedrootedDNRDNRDNRDNRwilted
Pineapple RedrootedrootedDNRDNRDNRDNR
Pineapple PrinceDNRDNRDNRDNRDNRDNR
Rustic OrangerootedDNRDNRDNRDNRDNR
SaturnDNRDNRDNRDNRDNRDNR
        
Perilla       
‘Magilla’rootedwiltedwiltedrootedDNRDNRrooted