Understanding Plant Nutrition: Poinsettias

Understanding Plant Nutrition: Poinsettias

Profit margins are extremely tight for poinsettias, so minimizing shrinkage that results from crop losses is essential. If nutritional stress occurs, you will be struggling from that point onward to produce a high-quality plant for sale.

Poinsettias hang around your greenhouse for several months, much longer than short-term spring crops. Therefore, a preventative approach that breaks the crop down into stages can help avoid the usual problems. Here are some pointers to consider at each stage.

Pointers

1. Poinsettias have four stages in which fertilizer needs vary: propagation, initial growth, rapid growth and flowering phases. Figure 1 represents the goals in each stage. The amount of fertilizer taken up by plants varies depending on how quickly the crop is growing.

2. During propagation, avoid solutions that have a high electrical conductivity (EC) (above 0.75 mS/centimeter) or fertilizers containing phosphorus to avoid foliar damage (Figure 3). Rooting can be delayed as mist-water EC increases, so use your purest water quality for propagation.

If stock plants were adequately fertilized, fertilizer is not necessary during the initial mist phase. If tissue nutrient levels in cuttings begin low (Figure 3), then it will be more important to apply nutrients early during propagation.

3. After one soil volume of water is leached out the bottom of the pot, any pre-plant nutrient charge contained in the growing medium will have been removed. Once roots emerge and misting is reduced, consider recharging nutrients with around 200 to 400 parts per million of nitrogen (ppm N) applied with a thorough irrigation to recharge the soil solution.

4. Control fungus gnats and pythium throughout the crop. Nutrient uptake is completely dependent on having a strong root system. If roots get stressed through pests, disease, high EC or overwatering, you will run into slow growth and sometimes deficiency symptoms.

5. During early growth, poinsettia elongation should not be “pushed” with extra fertilizer. Figure 4 shows an example of an experiment where fertilizer was either gradually increased (scheduled), or remained high throughout the crop (at 400 ppm N). Root systems were much stronger with a gradual increase in fertilizer EC.

6. Trends in media-EC with weekly in-house tests help you refine the fertilizer concentration. Choose whatever soil-test method you find most convenient and use the appropriate target EC values (pour-thru (1.9 to 4.1 mS/cm), 1:2 (0.6 to 1.5 mS/centimeter) or saturated medium extract (1.1 to 3.0 mS/centimeter)).

The fertilizer ranges in Figure 1 provide a reasonable guide, but we have provided a range not just to be vague, but because the “best” fertilizer rate depends on a number of factors in your situation. For example, light-colored foliage plants tend to require a higher fertilizer rate than dark-leafed cultivars. Slow-growing cultivars, such as variegated and Winter Rose types, have greater leaf expansion and vigor with moderate, rather than high, fertilizer rates.

Irrigation practices also have a big effect on required fertilizer concentration. For example, research at Michigan State University showed poinsettias could be adequately fertilized either with 100 ppm N and no leaching (such as subirrigation), or 400 ppm N with 55 percent of solution leached with each irrigation. Fertilizer rates in Figure 1 represent constant fertigation (fertilizer applied with each irrigation). If you apply regular clear water or fungicidal drenches, a higher concentration is needed whenever you do fertilize.

7. Target pH levels for poinsettias are broad (ideally between 5.6 and 6.4) because poinsettias are not as sensitive to media-pH issues as some other crops, such as petunia and geranium. At the extremes, however, symptoms of micronutrient deficiency or toxicity can occur.

8. Remember, the total nutrient solution is a combination of your irrigation water and the fertilizer solution. Therefore, the ideal poinsettia fertilizer varies between locations depending on irrigation water quality. For growers with high calcium and magnesium rates in their irrigation water (60 to 80 ppm and 30 to 40 ppm, respectively), that is already at the level of most calcium-magnesium fertilizers. However, growers with more pure irrigation waters will need to use a fertilizer high in NO3-N that also contains both calcium and magnesium.

9. Calcium and magnesium can also be supplemented to avoid deficiency symptoms (Figure 5) and also to reduce botrytis infection of foliage. Calcium can be applied as foliar sprays during the bract expansion phase. The Paul Ecke Ranch, Ecke.com, has a detailed bulletin on calcium sprays in its Tech Help section. Monthly soil drenches with magnesium sulfate (Epsom salts) at 1 pound/100 gallons supplement magnesium. Do not combine magnesium sulfate with calcium fertilizers such as calcium nitrate in the same concentrated tank, or precipitation will occur.

10. As the crop approaches the middle of October, avoid fertilizers that have most of the nitrogen in the ammoniacal or urea form, for several reasons: (a) most ammonium-based fertilizers are low in calcium and magnesium; (b) there can be increased soft growth with ammonium; and © in extreme cases with cool temperatures and dark conditions, ammonium toxicity can sometimes occur (which appears as a marginal chlorosis and downward cupping leaves).

11. Post-production quality for the consumer is improved when media-EC levels are low at the end of the crop. Growers sometimes cut off fertilizer too early in production, leading to deficiencies during bract expansion. A safe approach, especially if you are growing multiple cultivars in the same irrigation zone that mature at different times, is to drop fertilizer level to around 100 ppm N for the last two to three weeks.

Conclusion

In reality, poinsettias tolerate a wide range of nutritional levels. You can grow by the seat of your pants and usually get away with it. However, when you can’t afford a mistake, it’s good review your fertilizer strategy for each of the four stages of production.

Leave a Reply

One comment on “Understanding Plant Nutrition: Poinsettias

More From ...
Hendriks-Half-Open-Roof_GGS

March 26, 2015

10 Greenhouse Products For First-Rate Growing Environments

From coverings to fork-lifts, greenhouse suppliers offer a variety of products to make growing easier. Check out the slideshow to learn more about these, plus several other products that can offer you value, versatility and durability.

Read More
Rose rosette on Knockout rose, April 2012. Photo credit: Alan Windham, University of Tennessee

March 25, 2015

$58 Million In APHIS Farm Bill Funding Will Support Horticulture Priorities

Nearly $58 million as been allocated by the USDA's Animal and Plant Health Inspection Service (APHIS) to support the industry's Plant Pest and Disease Management and Disaster Prevention Program, under Farm Bill Section 10007. The program will support mitigation efforts for specialty crops, including providing research and other funding to address plant pest and disease priorities for the specialty crop industry, including floriculture and nursery crops.

Read More
AFE scholarship_Ryan Dickson

March 25, 2015

AFE Educational Grant And Scholarship Application Deadlines Approaching

Apply now for American Floral Endowment (AFE) scholarships or educational grants. Applications can be found online. For educational grants for 2015-2016, applications must be submitted no later than June 1. Scholarship applications are due May 1. AFE will award $40,000 in scholarships for 2015.

Read More
Latest Stories
Hendriks-Half-Open-Roof_GGS

March 26, 2015

10 Greenhouse Products For First-Rate Growing Environme…

From coverings to fork-lifts, greenhouse suppliers offer a variety of products to make growing easier. Check out the slideshow to learn more about these, plus several other products that can offer you value, versatility and durability.

Read More
Rose rosette on Knockout rose, April 2012. Photo credit: Alan Windham, University of Tennessee

March 25, 2015

$58 Million In APHIS Farm Bill Funding Will Support Hor…

Nearly $58 million as been allocated by the USDA's Animal and Plant Health Inspection Service (APHIS) to support the industry's Plant Pest and Disease Management and Disaster Prevention Program, under Farm Bill Section 10007. The program will support mitigation efforts for specialty crops, including providing research and other funding to address plant pest and disease priorities for the specialty crop industry, including floriculture and nursery crops.

Read More
AFE scholarship_Ryan Dickson

March 25, 2015

AFE Educational Grant And Scholarship Application Deadl…

Apply now for American Floral Endowment (AFE) scholarships or educational grants. Applications can be found online. For educational grants for 2015-2016, applications must be submitted no later than June 1. Scholarship applications are due May 1. AFE will award $40,000 in scholarships for 2015.

Read More

March 25, 2015

13 New Shrubs You’ll Find At The 2015 California …

Woody ornamentals serve as the foundation of many great landscapes, but beyond their traditional uses, shrubs also add color, structure, texture and interest to small gardens and even containers. Check out this slideshow to see some of the newest introductions you’ll get to see at this year’s California Spring Trials.

Read More

March 25, 2015

NASS Reports U.S. Honey Production Was Up By 19 Percent…

Honey production in 2014 from producers with five or more colonies totaled 178 million pounds, up 19 percent from 2013, according to a March 20 report from the USDA's National Agricultural Statistics Service (NASS).

Read More
Bloomtown_Screen Shot 2015-03-10

March 24, 2015

Bloomtown Exposes Consumers To The World Of Horticultur…

A new web series called Bloomtown is all about the mud, sweat and tears of horticulture. Filmed in St. Louis, Mo., it chronicles the world of horticulture using local flower growers, greenhouses, wholesalers, florists, consumers, retail shops and arborists, with the goal of opening consumers’ eyes to the world of horticulture around them.

Read More
OxiPhos_BioSafe2

March 23, 2015

BioSafe Makes Label Changes To OxiPhos And ZeroTol 2.0

There have been some recent label changes made to the BioSafe Systems product OxiPhos, a systemic bactericide/fungicide that reduces downy mildew spores when tank mixed with ZeroTol 2.0.

Read More

March 23, 2015

UF/IFAS Appoints Joseph Albano As Director Of Mid-Flori…

The University of Florida's Institute of Food and Agricultural Sciences (UF/IFAS) has a new directors for its Mid-Florida Research and Education Center (REC) on Apopka, Fla. The role has been filled by Joseph Albano, a research horticulturist from the U.S. Department of Agriculture with more than 25 years of experience.

Read More
Nufarm_logo

March 23, 2015

Nufarm Fungicides Now Registered For Use On Edible Crop…

Nufarm Americas announced label expansions for two of its fungicides that will provide more pest management options for the ornamental industry. The Cleary 3336 F and EG fungicides are now registered for use across a wider range of edible crops, including select greenhouse vegetables and transplants, herbs and backyard fruit.

Read More

March 23, 2015

Update To Armitage’s Greatest Perennials & Annuals …

A new update to the Greatest Perennials & Annuals app narrows the gap between consumers and grower-retailers, while providing more of Armitage’s top picks and growing advice for success with plants.

Read More
Plantbid website screenshot

March 20, 2015

Plantbid Brings Open Sourcing To Greenhouse Growers

Plantbid bridges the gap between buyers and sellers for sales and marketing networking on their own terms. The web-based, plant-sourcing platform aims to save growers time and make the business of buying and selling plants more efficient.

Read More
National Floriculture Forum 2015 029

March 18, 2015

2015 National Floriculture Forum Focuses On Marketing I…

The 2015 National Floriculture Forum, held March 6 to 7 in Minneapolis, Minn., zeroed in on the topic of marketing in horticulture and included visits to Gertens Greenhouses and Garden Center, Bailey Nurseries, Bachman’s Floral, Home and Garden and Tangletown Gardens. The annual meeting allows greenhouse and floriculture faculty, graduate students and industry partners to meet and share updates on current research, issues and initiatives.

Read More

March 18, 2015

H-2B Situation Goes From Bad To Even Worse

On March 5, the Department of Labor (DOL) announced that it will no longer accept or process H-2B labor certifications or requests for H-2B prevailing wage determinations in light of a March 4 decision. Shortly after the DOL announcement, the Department of Homeland Security's (DHS) Citizenship and Immigration Services followed suit, announcing it will at least temporarily cease approving visa petitions. These announcements essentially shut down the H-2B program for any company that has not completed the DHS H-2B visa petitioning process.

Read More
SAF CAD

March 18, 2015

Growers Ask For Immigration And Healthcare Reform Durin…

Nearly 90 growers, retailers, suppliers and wholesales attended the Society of American Florists' (SAF) 2015 Congressional Action Days March 9-10. The delegation, representing 18 states, arrived on Capitol Hill at a time when two major industry issues - immigration and healthcare reform - are especially prominent in national headlines.

Read More
2014 Poinsettia Season Report

March 18, 2015

Download Greenhouse Grower’s 2014 Poinsettia Seas…

Poinsettia growers report a strong year in 2014, thanks to a few conditions. Seasonal cold at just the right time put consumers in a festive mood to buy early and often, and with no big snowstorms to hold up shipments and a reduction of supply available in the market, the season was strong from start to finish. Greenhouse Grower’s 2014 Poinsettia Survey received 143 responses from growers around the country. Here, you can download the complete results of the survey, by filling out the form.

Read More

March 17, 2015

Pike Nurseries Implements Employee Stock Ownership Plan

Independent garden retailer Pike Nurseries has announced it will become an employee-owned company. Pike Nurseries management has combined with its sister corporation in California, Armstrong Garden Centers, to operate under an established Employee Stock Ownership Plan (ESOP).

Read More
Hydrangea 'Endless Summer BloomStruck' from Bailey Nurseries

March 17, 2015

Michael Dirr Slated To Address Attendees At Hydrangeas …

Dr. Michael Dirr to deliver the keynote address at Hydrangeas 2015 conference, hosted by the Cape Cod Hydrangea Society in partnership with Endless Summer Hydrangeas. The conference will take place at the historic Heritage Museums and Gardens in Sandwich, Mass.

Read More
Bee on a Sedum

March 17, 2015

4 Key Pollinator Research Projects To Be Funded By Hort…

The Horticultural Research Institute will grant $125,000 in financial support for four key projects as part of the Horticultural Industry Bee & Pollinator Stewardship Initiative. The Initiative has three primary goals. First, to convene a task force to develop a bee and pollinator stewardship program, including creation of best management practices for plant production. Second, to identify and fund research that will help answer key science questions and fill gaps needed to design and refine the stewardship program. Third, to seek to positively position the horticultural community and its customers by collaborating with other compatible groups interested in augmenting pollinator habitat and protection.

Read More