Friday, October 07, 2011

Only half of my fall mum bloomed? What gives?

Fall is the perfect season for gardeners to finally be able to chop down their poorly placed annuals. But also, it can be a grand time to catch some mistakes.

Last fall, we planted some garden mums in our front flower bed for late season color. They looked grand. After they finally succumbed to late fall freezes. I simply cut them back thinking that they surely won't survive our winter. But one did.

Share photos on twitter with Twitpic So this lone garden chrysanthemum grew well in the flower bed enjoying its southern exposure with filtered shade from my crabapple and plenty of water. I anxiously waited for it to bloom. But wait! Did it mutate over the summer?

Why is only half of the plant in bloom? This is just crazy, or is it?

So what is the issue. Some of you are saying, "C'mon Steve, you're such a dummy, you have landscape lights in front of the plant and that is throwing off the photoperiod. Photoperiod? Ray Kessler at Auburn University explains this well on his Chrysanthemum web page.
The chrysanthemum is a qualitative short-day plant with respect to flowering with temperature modifying the photoperiodic response. Plants flower when the day-length is shorter than the critical day-length and grow vegetatively when the day-length is longer than the critical day-length. However, chrysanthemums have two critical photoperiods, one for floral initiation and a different one for flower development. However, there is no single critical photoperiod because it can vary depending on the cultivar and temperature.
Look closely and you will see that there are landscape lamps on both sides of the plant. These are very inexpensive solar LED landscape lamps and their light quality is very much to the blue spectrum. So this can not be the problem. Photoperiodsm is controlled by red and far-red light, the other end of the spectrum from these LED's output. BUT, what you can not see in the photograph is that there are lights on the front of my garage, which we leave on at night for some security and those bulbs are 100 watt incandescent bulbs. The garage lights are the culprit. Incandescent bulbs generate a lot of red light, which is causing the light polution that is slowing down the bloom on the right side of this plant.

Will it ever bloom? Eventually, but probably not before first frost, which may come this weekend.

Friday, August 05, 2011

Research Progress Report on Floriculture Crops -- 1947-48

Today our department office manager handed me a document from Professor Holley's file that they have been archiving. It is a research progress report from 1947-48 and it reviews the research accomplishments from that year.

The most interesting information that I found while reviewing this is that many of the issues we currently have with floriculture crops is not very new. Insects, disease, and plant productivity. I only wish that now I could build a research greenhouse for $60,000. But in a testament to these scientists, the greenhouses that they built are what we are using today, albeit with a few upgrades.

I invite you to read and enjoy this document.

Research Progress Report on Floriculture Crops -- 1947-48

Thursday, August 04, 2011

History of Colorado Flower Growers

When my family and I moved to Colorado 14 years ago, the cut flower industry was still strong. Although the few cut flower growers that remain are among the best in the world, they are few in numbers. One of the best publications that was presented to me by the then Colorado Greenhouse Growers Association Executive Director, Bob Briggs, was a copy of Dick Kingman's book, A History -- Colorado Flower Growers and It's [sic] History. This book was published in 1986 and is a testament to greenhouse growers committed to Colorado and the cultivation of flowers.

Through the wonders of technology (and a new high speed copier/scanner in the office) I have placed a copy of this book on my website:

A -- History -- Colorado Flower Growers and It's [sic] People

If you would prefer, I have a few copies available for a small donation to CSU Floriculture.

Wednesday, June 22, 2011

Program Planning for Greenhouse Activities at Colorado State University

While proceeding on some very badly needed spring cleaning, I found another document that I seem to find relevant, even though it is over 35 years old. What I have found is a document on the Program Plan for Remodeling and Expansion of Facilities at the W.D. Holley Plant Environmental Instructional-Research Center at Colorado State University. As our department advances its teaching, research, and extension programming, it will be important to review documents such as this.

You can view the document at:

I invite your review and comments

Wednesday, June 08, 2011

CSU Floriculture Research Archives

One of the great pleasures that I have had during the past 17 years at Colorado State University has been the inheritance of a plethora of work that was done by former floricutlure and greenhouse faculty at Colorado State University. For years, these filing cabinets have been sitting in a closet awaiting an opportunity for sharing. Every year, I get a few requests from researchers and growers around the globe requesting a reprint, which I am happy to say, I can provide.

Electronic technologies now allow for me to put these items online. Our department now has a copy machine that will scan documents rapidly and with Adobe Acrobat, I can clean them up, capture the text, and save them in a format useable to you.

My first posting is a long favorite bulletin of mine,

Hydroponics, by Professors Joe Hanan and Bob Holley.

Yes, the publication is more than 35 years old, but the information is still relevant.

You can find this document and future installations on my Floriculture Research page.

Monday, March 07, 2011

Light Emitting Plasma Diode Lights for Growing Plants in Greenhouses

I became interested in light and light quality while in high school. Everyone had a set of black light posters in their bedrooms. A black light is actually a lamp that generates ultraviolet light that we cannot see. The light emitted is UVA (400-315 nm) radiation. This is not UVB (315-280 nm), which is harmful. Human normal vision perceives light between 380 and 760 nm. When a black light bulb shines on a poster with fluorescent dyes, it will glow brightly. What you see glowing are phosphors.

Modern laundry detergents contain phosphors that will convert UVA radiation to white light. This is why white T-shirts glow brighter than in normal sunlight. So, don't wear a white shirt when playing laser tag, you will lose (a dirty trick played on me by my teenage sons, I will admit).

But this is not the purpose of this article. Light manufacturers have been designing bulbs for growing plants for as long as we have wanted to grow plants indoors. Lamps include incandescent bulbs, fluorescent tubes, high pressure sodium, metal halide, and mercury vapor bulbs. There have been many advances in bulb design including dual spectra and switchable lamps. New advances in light emitting diodes (LED) are changing the types of lighting we use for plant growth at an exciting rate. (for more information, go to LED Lighting in Horticulture)

The critical issue when choosing a light source for growing plants is to understand the action spectra plant growth. Plants absorb light primarily in the blue and red wavelengths. Conversely, plants reflect light in the green wavelengths. The challenge for adopting lamps for growing plants indoors has been choosing the right bulb. Most lamp manufacturers report their lamps in terms of color temperature. What we think of as cool colors, blueish white, are at temperatures over 5,000°K and warm colors, yellowish white through red, are at color temperatures between 2,700-3,000°K.

Color and light perception has been long studied and human color perception was first elegantly displayed in 1931 by the Commission Internationale de l'Eclairage (CIE) and advanced in 1978.

1931 CIE XYZ Chromaticity Diagram

1978 CIE L*U*V* Chromaticity Diagram
 We can then overlay color temperature onto the CIE diagrams.

Which looks more like this for individual lamps:

Most professional growing operations use high pressure sodium lamps, but this is likely to change in the future as lamp technologies improve. One new technology that we at Colorado State University evaluated was a light emitting plasma lamp or LEP. This lamp was introduced to us by the Polar-ray company in Boulder, Colo. The LEP lamp was the Stray Light PlasmaGrow G-1 manufactured by the Luxim Company. (for the design specifications on the exact lamp we used see: LiFi-STA-40-02) So we put it to the test.

John Ray, Floriculture Research Associate and Plant and Environmental Research Center Greenhouse Manager, and his practicum students grew four bedding plant species, basil, snapdragon, tomato and zinnia, under two supplemental light sources, high pressure sodium (HPS) and light emitting plasma (LEP). The lamp height between the two were adjusted so that all plants received similar levels of photosynthetic active radiation (PAR). The lamps provided 18 hours of supplemental light in a polycarbonate glazed greenhouse.

The spectral irradiance is displayed on the graph below:

As you can see, the lamps are not similar in spectra, but what is the impact on plant growth? Dry weight data between the four species showed little difference between the two light sources.

Which lamp would you choose? First, you would have to look at price. the LEP lamps are fairly pricey coming it at $1,350 compared to a HPS for around $300. Energy consumption however, may be a different story. The LEP lamp used consumes 273 watts where the HPS lamp used consumes 1,000 watts. So how does one determine efficiency?

Most lamp manufacturers will report their lamp intensity in lumens. Luminous energy is light output in the visible spectra. The luminous energy rating for the LEP lamp was 14,000 lumens and for the HPS lamp, 110,000 lumens. That makes the luminous efficiency for the LEP lamp at 51.3 lumens/watt and the HPS at 110 lumens/watt. But is that relevant?

There are two forms of chlorophyll, chlorophyll a and chlorophyll b. Chlorophyll absorbs the greatest amount of light energy at 430 nm and chlorophyll b absorbs the greatest amount of light energy at 662 nm. There are other carotenoids involved, but that is beyond what we are discussing here.

Which one do you choose? That is strictly up to you.

Wednesday, March 02, 2011

Can Rice Hulls be Used in Root-zone Media?

I have been following a lengthy debate on the use of rice hulls in root-zone media as a substitute for perlite.This debate is posted on the Fresh Air Forum sponsored by Greenhouse Grower and Today's Garden Center magazines. While the debate has been heated at some points, the one issue consistent in the discussions has been, what is the status of the research on the use of rice hulls in root-zone media.

From 1985 through most of 1994, I was on the faculty at Mississippi State University. Undoubtedly, rice is a major crop for Mississippi farmers and waste from the milling industry has always been an issue. Use of any agricultural waste by-product in root-zone media has always been an opportunity for discussion. Therefore, much of my research at Mississippi State was devoted to alternative media substrates ranging from pine bark to crumb rubber.

In 1994, one of my graduate students, Shelly Dueitt, conducted a fairly in depth evaluation of rice hulls, fresh and aged. I am choosing the term aged and not composted for a significant reason. Most rice milling operations did not actively compost their rice hulls at the time, but just created large piles. These rice hulls used in Shelly's study were uniform in age, just not composted.

Shelly blended six sphagnum peat moss-based media modified with rice hulls. They were evaluated during the greenhouse production of marigolds (Tagetes erecta) and statice (Limonium suworowii) as cut flowers. Seedlings were transplanted into media containing aged or fresh rice hulls at rates of 0 to 50%. Quality plants for each species were grown in all media compared to the control. Pore space for both the aged and fresh rice hulls was satisfactory for good water holding capacity. The bulk density of all media containing rice hulls was greater than the control. The addition of aged and fresh rice hulls increased the pH of the media. Rice hulls, fresh or aged, can be used successfully as a sphagnum peat moss substitute for the production of selected short-term cut flowers.

You can see a copy of her thesis at:
Rice hulls as an amendment to root-zone media is not new and was not new back when Shelly conducted her research. Here is an excerpt from Shelly's literature review:
The use of parboiled rice hulls in potting media as a soil or sand substitute in comparison to a peat-sand-soil mix was used to grow Lilium longiflorum Thunb. 'Ace' (Einert, 1972). Three-component media consisting of parboiled rice hulls, sand, peat, or soil was compared to a standard media of peat:sand:soil (1:1:1, by volume) and peat:sand (1:1, by volume) to produce 'Hibernia' and 'Paul Richter' tulips (Einert and Baker, 1973). The media containing parboiled rice hulls increased root growth (Einert and Baker, 1973). Einert and Guidry (1975) stated that composted rice hulls might serve as a soil substitute for container grown plants.
Rooted Juniperus chinensis 'pfitzeriana' liners were planted in greenhouse potting soil and cracked rice hulls and rice hull compost and cracked rice hulls at 20 to 80% of rice hulls (by volume) in each series of media (Einert and Guidry, 1975). A mixture of 1:1:1 (by volume) of sand, field soil, and peat moss were the components before rice hulls were added (Einert and Guidry, 1975).
Laiche (1989) stated that the use of composted rice hulls as an organic amendment for container media compared favorably with media consisting of pine bark alone when growing container-grown woody landscape plants. The composted rice hull medium produced the largest plants and highest rating for shoot quality and highest fresh weight for Ilex crenata 'Compacta' and Ilex vomitoria Straughn's selection (Laiche, 1989) These results indicated composted rice hulls as a single-component growing medium can be used successfully (Laiche, 1989).
Foster and Gilliam (1989) also stated that rice hull compost may be an alternative to peat moss for at least one growing season. Other studies conducted by Laiche and Nash (1990) indicated that a good replacement for pine bark may be composted rice hulls in container media. Media consisting of both 50% and 100% composted rice hulls produced plants with growth that compared favorably with 100% pine bark (Laiche and Nash, 1990). Acceptable growth of three azalea cultivars were obtained by amending media containing pine bark with sand or compos ted rice hulls in comparison to peat moss (Laiche, 1990).
Selected literature cited here:
  • Einert, A.E. 1972. Performance of Rice Hull Media for Pot Easter Lilies Under Three Forcing Systems. HortScience. 7(1) :60.
  • Einert, A.E. and E.C. Baker. 1973. Rice Hulls as a Growing Medium Component for Cut Tulips. Journal of the American Society for Horticultural Science. 24(3) :2.
  • Einert, A.E. and G. Guidry. 1975. Media for Container-Grown Junipers. Arkansas Farm Research. 24 (3) : 2.
  • Foster, W.J. and C.H. Gilliam. 1989. Container Media: Rice Hull Compost. Volume 34. Southern Nurserymen Association Research Conference - 34:93-94.
  • Laiche, A.J., Jr. 1990. Effects of Media Blends of Pine Bark with Peat Moss, Fresh Pine Wood Shavings, Composted Rice Hulls or Sand on the Growth of Azaleas. Southern Nurserymen Association Research Conference - Volume 35. 35:119-122.
By the way, The Southern Nurserymen's Association Research Conference Procedings are online from 1974 to present. There is lots of information here that you will not find anywhere else.
Shelly's work concluded that, quality plants for each plant species were grown in all media compared to the control. The dry weight of marigolds and statice were similar to the control. Pore space for both the aged and fresh rice hulls was significant enough to have good water holding capacity. The bulk density of all media containing rice hulls was greater than the controls. The addition of aged and fresh rice hulls increased the pH of the media. Soluble salt levels of both rice hull media were not different from the control initially, but after plant growth the soluble salts were less in media with rice hulls. Rice hulls, fresh and aged, can be used successfully as a sphagnum peat moss substitute in a sphagnum peat-based media for short term selected cut flowers. The amount used as the media substitute will depend on the crop to be grown.

The bottom line is, to use rice hulls as a component of a root-zone media, it must be aged or composted. Fresh rice hulls will result in poor plant growth, volulnteer rice seedlings, and hungry rodents.

Monday, February 21, 2011

Questions and Answers - Hydroponics Panel at ProGreen EXPO 2011

ProGreen EXPO 2011 in Denver earlier this month was a great success. This annual event is the single best regional green industry show in the Rocky Mountain West. There were over 140 seminars on both the most basic and the hottest topics in the green industry, plus over 650 exhibit booths of interesting products and services.

On the final day at ProGreen, I hosted an open panel on hydroponic greenhouse production with three nationally recognized experts in hydroponics. We spent an hour responding to questions from the audience. The dialogue is summarized below.

Who were the panelists?

Questions from the audience with answers from the panelists:

Recently, the Oregon Department of Agriculture released a stop sales order on many fertilizers that are not legal for sale or distribution in the state of Oregon due to failure to register. What is the opinion of the panel on this issue?
First, the State of Oregon is trying to protect the consumer from fraudulent products and fraudulent claims that often result from untested or unregistered fertilizer products. Next, their intention is to protect the environment from inappropriate use of fertilizers resulting in excess runoff into the waterways.
The rule making organizations that are creating and enforcing the rules do not always have all of the knowledge that they need to make appropriate decisions. Therefore, they rely on the registration procedures that they have developed and are trying to support those companies who manufacture products based on good science. The majority of the products on the stop sales list are either not registered with the state of Oregon or are mislabeled.
What is the suggested filtration process for disposing hydroponic wastes?
Hydroponic solutions that are no longer useful for maintaining plant growth is high in fertilizers, dissolved solids, and potentially plant pathogens. It is not appropriate to dispose of these solutions as storm water or sanitary sewage.
The ideal disposal process is through bioremediation through application on secondary and tertiary crops. Ideally these should be plants you can sell, such as nursery crops or turfgrass sod. The waste solution needs to be drained, collected, and stored in a safe and efficient way. From there it can be pumped outdoors to a turfgrass site or other outdoor crops.
Treatment of the effluent using reverse osmosis is expensive. The use of constructed wetlands is an additional alternative worth exploring.
Can the wood from Mountain Pine Bark Beetle killed trees be used as a hydroponic substrate?
Pine bark is a very effective growing medium for hydroponic production and has been used by many growers successfully. There has been a great deal of research conducted comparing sphagnum peat moss, coconut fiber, etc. (see the Mississippi State University Greenhouse Tomato Handbook).
Pine wood waste is high in cellulose and requires composting to make good soil substrate. Pine bark is high in lignin and resistant to degradation. 
The biggest issue with the use of beetle-killed trees is access. Most of the trees are in hard to reach areas and the expense of harvest, shipping, and processing makes this product cost prohibitive.
Many of the tomato cultivars that we are growing taste terrible. Are the varieties getting better and what is the future of tomato selections?
Flavor of tomatoes grown in the greenhouse is based on solar load, the pH of the hydroponic solution, and the nutrient status of the plants. Greenhouse production in the spring (Mississippi) provides more sun than the fall, which yields better tasting fruit. Most people like an acid flavor with the sweetness. The pH of the solution does have an impact.
What about varieties? Seed suppliers base their product lines somewhat based on what customers want. Older varieties (heritage included) lack modern disease resistance. Yet, many customers think that older varieties have better flavor.
De Ruiter Seeds, one of the largest greenhouse vegetable seed suppliers, is now owned by Monsanto. Their corporate approach is to determine the best seed sales and eliminate those varieties that do not meet market demands. Therefore, they are eliminating some varieties that are not selling well on an international scale. Ultimately, this is resulting in the loss of some good varieties, such as Blitz.
Summer tomatoes tend to taste better in summer due to stress due to heat and water stress. Pushing yields to compete with field growers is probably costing us some flavor.
Grafting heirlooms onto modern cultivars with more disease resistance will improve yield and flavor.
What is the projected yield on grafted heirloom tomato cultivars?
The first fruit cluster will yield well and then dwindle on future clusters. Genetically, most heirlooms will behave determinately and not bear fruit over the long term.
Do we have tomato cultivars that have higher nutritional content?
The longer tomato fruit are kept on the vine, the higher the nutritional value and flavor. Fruit harvested green or as breakers will not yield the best flavor. This is the same for hydroponic and field production.
Are there programs breeding tomatoes for higher nutrition?
Most tomato breeders are working on increased yield and disease resistance.
What is the difference between natural sunshine and artificial light? Does artificial lighting grow plants just as good as natural sunlight?
The answer is yes and no. High pressure sodium lamps do grow good plants, but it does not provide adequate heat stress on the plant resulting in some loss of flavor. There is a considerable amount of effort on LED lamps. Those on the panel did not have any specific experience, but are paying attention to the literature.
For the best wavelengths to grow plants, use light sources that provide PAR (photosynthetic active radiation) lighting. Remember that light intensity drops significantly as distance from the lamp increases. Northern European growers use high pressure sodium to extend photoperiod primarily, but their electric power is cheaper than what we have in North America. In Colorado, with few cloudy days, supplemental light is probably unnecessary. It is difficult to acquire the appropriate solar load, which leads to high costs for tomatoes. Other crops with higher value may benefit from lighting.
What is the appropriate spectrum for growing tomatoes under artificial light?
High pressure sodium lamps have poorly balanced red and blue spectra, but plants seem to grow well. There is a great deal of LED research for supplemental light in the proper blue-red balance is underway at many research centers.
Blue light, such as that from metal halide lamps, has shown plants to become more susceptible to insect infestations. Blending light from high pressure sodium with T-5 fluorescents will add some blue for a better balance when using high pressure sodium.
When using coconut fiber (coir), should it be charges with fertilizer for earlier cluster yields?
Coir is the dust and fibers from the mesocarp of a coconut fruit. It can be a great resource for growers as a root substrate because it is available in large quantities and is an agricultural waste product. However, coconut palm trees are resistant to high levels of sodium and grow in coastal areas. Therefore, some coconut fibers are high in sodium. Some processors do not rinse their product well prior to compression. Fresh coconut fiber should be soaked in a solution in calcium nitrate overnight will push out the sodium (total use a calcium nitrate solution with an electrical conductivity of 3 or 4 dS/m). 
What plastics are best used for the floor of a tomato greenhouse?
White plastic is reflective increasing light distribution, but the plastic used needs a uv inhibitor blended during its manufacture. Black plastic does not degrade as quickly as white, but it does not provide reflection. There are plastic products available that are co-extruded with white and plastic layers, but they are expensive. Consider using food-grade polyethylene for your plants. Polypropylene is also an option. Remember, black plastics can be painted white.
What is the best way to recycle rockwool used as a root substrate?
Rockwool is widely used in Europe and they have mandatory recycling programs often incorporating it into asphalt. Some growers have tried to recycle rockwool into potting media for bedding plants, but the issue of removing the plastic and the plant debris makes this practice cost prohibitive.