Could use some advice on shading vs. not shading. I have a house full of points, including Freedom Red, White, Pink, JB and Prestige Red. All potted up between 8/8 and 8/10. Have had 60% shade on from the beginning. Plants seem O.K. so far with temps as high as 95 in house each day. Here in middle Georgia, it has been from 98 to 105 every day since about 8/7. Yesterday, 8/21, at 10:30 A.M., light levels were 3,000 FC with shade on; temp was 92 inside. After removing the shade, light was 7,500 and temp rose to 102 very quickly. Put shade back on after 45 minutes.

Questions: What temps are O.K./excessive given these light levels? Should I gradually acclimate the plants to the heat and light;e.g. remove shade cloth a few hours daily up to a point and then leave it off? How hot is too hot? How bright is too bright?

I personally would not consider removing the shade cloth until you are sure you can keep the greenhouse day temperatures in the high 80's or even lower. As I have reported in the past I now grow my entire crop from August to December under 50% shade due to our excess light and temperatures on the Texas Gulf Coast. On some occassions we have 90 degree outside temperatures here even at the end of November. With the new PGR's on the market Poinsettia stretch from any shade can be easily controlled if one uses consistant tracking and scheduled applications...Michael Pawelek

I live in WI. I planted my cuttings around 7/9. I am using a 50% shade cloth this year. Without the shade cloth, my temp rose in the 100's. My points are doing good with very little if any stretching. Thanks to Michaels earlier posting on shade cloth, I gave it a try this year.

Yeah, Michael gave us the courage to leave our shade cloth on later -- thanks, Mike!
Here in northern VA, we leave it on until the middle of September, or theres abouts, depending on the temps. Everyone seems happier!

OK....first let's address light levels. Following transplant we like to see light levels at 3,000 - 4,000 f.c. When the shade cloth is removed if levels are 7,500 f.c. candles that is way too high and you will start to see some scorch from the excessive light levels. Once the plants have established and after the pinch the plants can handle higher light levels (5,000- 6,000 f.c.)and in fact these higher levels will produce a plant with much stronger architecture.

Now let's talk temps....ideally we like to see average daily temperatures at 73-78F but we know that especially for you folks in the south that just isn't possible right now (or much later in production for that matter!). Poinsettias can handle the extreme temps as long as they aren't under any moisture stress and light levels aren't excessive. When temps are really high misting or syringing the cuttings and providing good airflow will help the plants cool themselves. As we near flower initiation you do have to watch night temperatures though as temps above 72F (22C) can lead to delay on certain varieties.

Now let's talk about the interaction between light and temperature and the impact on plant quality. The best quality poinsettias are those grown at moderate temperatures and high light levels while the poorest quality plants are grown at warm temperatures and low light levels. The take home message here is that shading in the greenhouse will only cool temperatures so much so you don't want too much shade or quality will be reduced. When temps are warm the plants can handle the high light levels as long as they aren't too dry, and in fact you'll be happier with the plant structure if you keep light levels above 3,000 f.c.

It is also important to remember when we are talking about shading that contrary to popular belief shading or cloudy days is not what causes a poinsettia to stretch. It is actually neighboring plants and the competition for light that causes the plants to stretch, not shading or cloudy weather. The take home message here is don't be afraid to leave the shade cloth as long as necessary to control excessive light levels and help control your temperatures - it won't cause your plants to stretch.

This message has been edited. Last edited by: Ecke Ranch Tech Help,

Thanks so much everybody for your thoughtful advice. A few other questions as a followup-(1) is there an optimum light level for points-if so, what is it? (2) What would be a minimum acceptable light level/maximum temperature for my middle Georgia climate? (3) Should I respace the pots? I have them pot to pot right now. I have 6 1/2" pots with 1PPP, 8" pots with 2 PPP, and 10" pots with 3PPP.

Some answers to your questions...

1) Optimum light levels for poinsettias are 5,000-6,000 f.c. on a crop that is established and growing well.
2) Light levels below 3.000 f.c. will produce a crop with weak branching and poor architecture. In Georgia it will be difficult to control the temperature through much of the season. Ideally you want your average daily temperature at 73-78F but that probably just isn't possible. Control your temperatures as much as possible and when the temps do rise mist or syringe the cuttings and provide good airflow to help the cuttings cool themselves. Keep your light levels up for a quality crop - don't worry so much about temps as long as the cuttings aren't dry and stressed!
3) If you are thinking about spacing the crop there are some things to consider. Spacing plays a big role in stem elongation. We talked earlier about the plants stretching because of neighboring plants and competition for light. Poinsettias recognize they have a neighbor when their leaves begin to overlap with their neighbor. We call this canopy closure. More canopy closure = more stem elongation. If you space too early before there is much top growth after pinch you might find that the plants don't elongate fast enough and lead to height issues later. Before you space evaluate canopy closure and make sure you need to space. If spacing is needed, go to an intermediate spacing and maybe not final spacing. Leaving the plants at a tighter spacing also helps raise the relative humidity level around the plants and keeps the soil moist longer. This will reduce stress when the temps are high.

Thanks, Ecke.
More clarifications on heat and spacing.
You say not to worry too much about heat as long as plants aren't dry or stressed.

Heat-(1) Its obvious what "dry" is, but what exactly constitutes "being stressed" or "not being stressed?" (2) Are temps in the triple digits too high? (3) When misting or syringing, how many times per day? During the hottest part of the day? (4) Would a new shade cloth with, say 30% shade (have only 60% shade now), be advisable in order to raise light levels from 3,000 FC? Or am I too late for this? Keep in mind that plants have not been pinched as yet.

Spacing- (1) Is stretching even an issue before pinching or only after pinching? (2) What would an intermediate spacing be? Would it mean plant leaves just barely touching or just inches away from touching? Do you buy the "V" growth idea I've read about or should I be concerned about the horizontal growth of breaks leading to potential stem breakage, etc.? (3) You mentioned canopy closure. Exactly how would I evaluate "canopy closure" and thus know when to space?

Tim, Below are some pictures of "stressed" Poinsettias from excess light and heat. Though Prestige is one of the toughest and strongest branched Poinsettias I have ever grown they appear to be the most sensitive to excess light and heat and will show a definite leaf curl when stressed. These pictures were taken in November right after the color stage began on this crop and the Poinsettias were well watered. Once they curl to this point day after day I believe some minor root damage can occur. They would only do this in the "heat" of the day and by the next morning would look fine. This was the year I decided not to grow my crop under full sun this far South and since then have never had this problem again.
..Michael Pawelek


I re-applied the shade cloth and this is what the crop looked like 35 days later.....

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

Tim, This is what I consider as "intermediate" spacing....Michael Pawelek

Hi Tim -

Without knowing what your greenhouse environment is like it is really hard to tell you exactly where your levels should be.

Triple digit temps are excessive....but can you get it any cooler? Many growers in the south will tell you this is pretty common this time of year. You should try and keep temps below 85F but is that possible? If it is possible that's great, if its not possible than you have to deal with what you have reduce the cuttings stress while temps are high. Now you ask, what is "stressed". When temps climb the cuttings have to transpire very fast to cool themselves. This fast rate of transpiration requires a high level of moisture availability. If water isn't readily available you will see the margins roll and possibly even burn. The root zone can also get very hot and actually burn the root tips. That's why we recommend syringing or misting. Both should only be done during the hottest part of the day because we also have to worry about overwatering and over saturating the media when the roots aren't completely established. Misting will help cool the leaf surface fast while syringing with cool, clear water will rapidly cool the root zone.

Now light levels....if the plants haven't been pinched 3,000 f.c. is an appropriate light level. If keeping the f.c. at 3,000 is helping reduce your temps than leave the higher percentage shade cloth on for now. Later, once the plants are pinched and new shoots are actively growing hopefully things will be cooling off for you. At that point the crop will probably still require some shade and you should use the lower percentage shade cloth and aim for light levels closer to 5,000 f.c.

Spacing....canopy closure is a way to measure how many leaves are over lapping. Ideally, spacing should happen when the leaves are just beginning to overlap. Stretch can occur prior to pinch but plants are usually left pot tight until pinch. Intermediate spacing is just what it sounds like, not pot tight but not final spacing. On newly pinched plants that have just been spaced the leaves probably won’t be touching with an intermediate spacing.

The "V-shaped" growth idea is very important in reducing stem breakage. Shoots that form more horizontally are the ones that break later in production. The mature stems become too heavy for the plant to support. Proper pinching techniques and good light levels after pinch are very important when it comes to getting the v-shape. Cultivar selection is also important. Prestige has a natural v-shaped architecture and strong stems while cultivars like Freedom tend to have more horizontal branch formation and more problems with stem breakage.

Thanks, Michael and Ecke, for your good words. I went ahead and removed the shade cloths from my houses late Sunday evening and on Monday light levels measured between 4,000 and 6,000 FC inside (10,000 FC outside). I have not pinched yet. I respaced them from a tight pot to pot to an intermediate spacing as shown in Michael's picture. So far so good. Only a very minimal amount of leaf curling and stress has been observed, even though temps have been as high as 101 degrees inside. Milder outside temps here in middle Georgia (90-94) and some cloudiness have helped. Have not done any misting as yet, but plants are well watered, fed, and aerated. Thanks again for your timely responses. I think I am O.K. for now.