In the last week, my crop has really turned very very yellow. My pH's are ranging from 5.9 to 6.4. My ec's are ranging from 1.5 to 3.0. The yellowing is overall, starting from top (bracts) moving towards bottom. Everyday I walk in and they look yellower. Also noticing a last minute stretch occuring. Do I need to keep fertilizing, is that why they are yellowing. Last 2 waterings have been with clear water. Up until that I've been fertilizing constant with 15-4-15 poinsettia feed at 200ppm. Just this week I switched to 20-10-20 becauce I felt like my pH's were getting to high. At first I thought the yellowing was happening because they are turning color. But now I think I'm dealing with something different. The Prestige started first but now I'm seeing the yellowing in just about every variety. Also I turned my temp back everyweek in the last 3 weeks slowly. Starting out at 68 and moving down to now 58. Our day temps in the greenhouse are still pretty warm everyday getting to at leat 85 and on some days to 90 or above. The roots look great. I'm seeing it throughout different sizes too. But the worst of it seems to be on 6-1/2" and 5" pots. What can I do to make them greener? quickly?

Denise, Even if your pH and EC levels are in a targeted range it does not mean the Poinsettias are getting the correct nutrition. Remember that E.C. is just a reading of total soluble salts in the soil, both good and bad, and you can still be high or low in any given single element. It is my experience that most commercial fertilizer mixes, even those specific for Poinsettias, may not be a good source of calcium, magnesium and Molybdenum. If your EC levels are determined by the "pour thru" method a 1.5 is on the low side of the range .You might want to have a soil and tissue analysis done for this and future crops to see what element(s) may be high or low in this particular crop.

On the night time temperature issue...There have been recent articles on dropping temperatures on Poinsettias earlier in the crop cycle to save on fuel costs but this has not become a standard practice as of yet and until more study is done I believe you need to keep your night temperatures around 68F....Michael Pawelek
PS- Can you post some pictures please?

This message has been edited. Last edited by: Michael Pawelek,

I've posted some pictures of what my situation looks like. I am not sure if I have enough time to send sample to lab? The turn around time is usually 5-7 days and by that time is it too late? Do you think it is nutrient problems? I can't understand why I'm seeing such a difference between plants grown on the same bench side by side. They are on the same watering schedule and fertilizer schedule. Any suggestions from anybody will be great.

Hi Denise -
Thanks for the images...picture always help give us a better view of the situation.

Yellowing like this that begins with the new foliage makes us think of iron deficiency. Low levels of iron, high media pH (6.5+) or excess manganese can lead to iron deficiencies. The only way we would know for sure would be to send a sample out for testing. It does seem like there isn't enough time but there are some labs that can rush results and you can have them within 24 hours. JR Peters is one example. We would actually encourage testing because if in fact this is an iron deficiency it can be corrected easily. Iron deficiencies and high media pH can be correct with an iron sulfate or iron chelate fertilizer application but we don't recommend doing this until you know for sure what's causing the yellowing.

We would caution increasing fertility rates and using the 20-10-20 right now. The acidity of the 20-10-20 will help reduce the pH but it is too much ammoniacal nitrogen at this stage in the crop. It can lead to ammonium toxicity and is probably contributing the stretch you are seeing because ammoniacal nitrogen encourages soft tissue growth. By the end of October to early November growers make the switch to a nitrate based form like the 15-4-15 you were using because it helps tone and slow growth and get the plants ready for the retail environment. You also want to be decreasing your fertility rates right now and allowing the EC levels to drop in the soil. Here's a good reference to check out: Fertilization . Recommending that you decrease rates right now may seem strange considering you might be dealing with a nutrient deficiency but increasing rates alone probably won't correct the yellowing and before you try to correct the deficiency it is important to know for sure what is causing the yellowing. It looks like you are also using the cold growing technique and dropping temps. Remember at the colder temperatures the plants nutritional needs will be much less as there growth rate slows significantly. They are also going to be using a lot less water with the cold night temps so make sure to adjust your irrigation schedule to reflect the changing moisture needs. Root rotting diseases can damage roots also and affect nutrient uptake and lead to deficiencies.

There’s a lot of info to process here but the bottom line is that if you are concerned about nutritional issues it isn’t too late to send out a sample, then take steps to correct the situation once you have all the information in front of you.

Should I do tissue and soil samples or just tissue samples?

Hi Denise - Tissue and soil will give us a better picture of what's going on. What happens in the tissue is a reflection of what was happening in the soil 7-10 days ago so soil tests will tell us what is happening right now.

I think it would be interesting to check the leach volumes during an irrigation cycle on a green pot and a yellow pot. Also check ph and EC on these samples. We have very hard water with a high ph. In the past I have had ph or fetrilizer issues with injectors to the point that by the end of a crop all drippers may not be dripping the same. In my instance a dripper slows down or plugs... EC in that pot goes up... ph goes up.. plants stand out...and strange things show up in the tissue analysis of those plants! Just an idea.

Also,I agree with everyone else about the tisue analysis. Even if it is too late for this year it may help prevent the problem next year.

Im thinking I would cut the poinsettia feed, and go straight to a cal/mag @ 150-200 ppm. Plantex 14-0-14 is good as strech will be reduced, but that 2:1 cal/mag ratio is important. You may be able to throw one or two Calcium sprays in there too. A friend of mine brought in her point trees she has kept throught the years for me to winter over. And they were very yellow, but after the cal/mag and spray it greened them right up.