Top 10 Poinsettia Mistakes By Roger C. Styer

Learning how to avoid these mistakes will lead to a healthier, more profitable poinsettia crop.

Well, believe it or not, it’s time for anotherpoinsettia season! Some of you are already tired of poinsettias, having donepoinsettia stock plants since last spring. Other growers are just rootingbought-in cuttings and potting up finished containers. Even though it ismid-summer, poinsettia growers have a long way to go before they can ship theirpoinsettias. During that long period, many things can go wrong. I’veboiled down the major mistakes I see poinsettia growers making, along with somesuggestions to avoid them. See if any of your mistakes are on this list!

10. Stem Breakage

Unfortunately, this mistake doesn’t show up untilshipping, when plants are picked up and sleeved. At this point, it really istoo late to do anything with them other than try to tie them up. I’veseen a few growers actually cry when this happens. However, many growers havebeen getting around stem breakage problems the last few years by using rings.

Stem breakage can be due to several factors: 1) choice ofvarieties; 2) spacing too early, causing branches to grow at 90-degree angles;3) not enough calcium in feed; 4) poor control of lateral branches; 5) too manylaterals; 6) bracts too big and heavy; and 7) pushing plants with latetemperature to make height.

Basically, branches break because they are too long andheavy and grow at 90-degree angles. Some varieties are more prone towards stembreakage. Spacing later will force laterals more upright (30-degree angle).Developing stronger branches with calcium and proper growth regulators willhelp. Pinching to the correct number of laterals for the pot size will alsoprovide enough light and food for the laterals to develop correctly. Big, heavybracts will cause extra weight on the laterals unless supported by tying orrings. Pushing plants late causes soft growth and large bracts.

9. Botrytis

This disease presents problems during propagation and againduring bract development and shipping. Symptoms during propagation includebrownish spots that, under mist, develop rapidly to wipe out the whole leaf.Grayish spores may or may not be readily seen, depending on how much mist isused. During bract development, Botrytis can develop as little dark spots andspread over larger areas, making the bracts unsightly and the plant unsaleable.White, light-green leaf varieties tend to show Botrytis first.

Botrytis spores are everywhere in the greenhouse. Remember,these spores need free moisture on the leaves or bracts to infect. Keep areasclean of dead and dying tissue or plants. Wean cuttings off mist as soon aspossible. Give the cuttings enough space in Á propagation so leaves arenot covered up, providing more food for Botrytis. Watch your mist cyclesclosely at night and during cloudy days. For fungicide sprays, use Daconil,Chipco 26GT (or 26019), Medallion, Phyton or Decree at least weekly duringpropagation, starting about three days after sticking. Apply at end of mist cyclefor the day during the early stages.

For controlling Botrytis during bract development, make sureto ventilate and dehumidify greenhouses every day. You can dehumidify forapproximately one hour first thing in the morning and again before going homeat the end of the day. If watering plants overhead, make sure bracts are drybefore the end of the day. Use weekly calcium sprays at 300 ppm (calciumchloride) once bracts start showing, as this will toughen them up and make themless susceptible to infection. Finally, you can spray as needed with Phyton 27(low end of rate) or Decree (with spreader-sticker added). If using ExothermTermil, be careful about sensitive varieties or collecting too much on certainplants. Try not to hold crops longer than needed at cool temperatures.

8. Bract Expansion

Failure to properly expand bracts by ship date is usually aproblem with mid- to late-season varieties. This is due to early varietiesbeing grown with the later varieties in the same greenhouse zone. Once the earlyvarieties fully expand, temperatures are usually dropped to help hold them, notrealizing that the later varieties need a warmer temperature to fully developbracts. Best bract expansion is achieved with 68º F average dailytemperature (ADT). Holding Freedom varieties requires 60-65º F, well belowthe bract expansion temperature. Group mid- and late-season varietiesseparately from early-season varieties, or pay closer attention to how much youlower the temperatures.

Another reason bracts may not expand enough is too muchgrowth regulator. Constant late use of Cycocel can reduce bract size. But themain culprit in the United States is usually Bonzi sprayed too late or Bonzidrench applied too early. Cut-off dates for Bonzi sprays are early tomid-October in the Deep South and initiation in the North. For Bonzi drenchesafter initiation dates, wait until plants are about one inch from saleable sizeand have about 20 percent color showing. Drenching before this date will causedelay in bract expansion. For Freedom, this means the late Bonzi drench isusually applied the last week of October or later. For ‘Monet’,this means drenching about mid-November.

7. Pythium

Pythium, like Botrytis, is always around in the greenhouse,just waiting for the right conditions to attack plants. This disease showsmainly at the root tips and works upwards through the roots, collapsing plantseven when media is moist. Pythium can show up at any time on poinsettia roots,from propagation to shipping.

The main conditions that promote Pythium are those factorsthat hinder roots: 1) too wet, 2) high salts, 3) poor air porosity in media and4) low calcium. Use a well-drained media consisting of some larger particlesfor better air porosity. During propagation, avoid drying out wedges too far,as you will lose roots. Monitor soluble salts in the media and leach if needed.Avoid drying media too much, as soluble salts will build up quickly aroundroots. Incorporate calcium into your feed program. On Winter Rose varieties,set up the irrigation on a different schedule, as this variety does not dry outas fast. Fungicide drenches applied monthly will help. Use Banrot, Subdue,Truban or Terrazole, making sure to combine another fungicide for Rhizoctoniawith Subdue, Truban or Terrazole. Many growers are also finding good resultsincorporating a biofungicide into the media soon after potting, such asRootshield, Companion or Actinovate, and then drenching with fungicides asneeded later in the crop.

6. Fungus Gnats

This pesky little insect causes lots of headaches forpoinsettia growers during propagation and the first few weeks after potting.The larvae feed on roots, causing them to become more susceptible to root rots.You can recognize fungus gnat adults by their long, slim bodies, long antennaeand lazy flying pattern. The larvae have a black head capsule and feed ondecaying organic matter, including roots. Once you can get past the rooting outstages and into a normal wet/dry cycle, fungus gnats are not as much of aproblem.

For control, make sure to properly clean propagation andgrowing areas before poinsettia season starts. Knock down any adults withautofogs or sprays, and treat the dirt floors and drainage areas with a sprenchfor larvae (see Figure 1, Á below left). Get sticky cards up in yourpoinsettia areas to tell you when you have problems and how well your controlprogram is working. In propagation, use Gnatrol, Distance (sprench rate),Citation, Ornazin or Azatin, or Enstar II. Duraguard and Knox-Out will not workwell when media is wet all of the time, so save them for later. Adept is nolonger labeled for poinsettias, but you can use it on the floor. Nemasys(nematodes) will not work well in Oasis wedges but works much better indirect-stick production. Save the Marathon for whiteflies. Hypoaspis mites willwork well in conjunction with insect growth regulators, but they do not like toswim. You can broadcast them over pots once they’re off of mist andbefore plants grow very big and are spaced. They will scavenge across the mediasurface and feed on fungus gnats and shorefly larvae, and any thrips that arein the soil.

5. Not Knowing the Varieties

It used to be we only had a few poinsettia varieties togrow, so growers got very accustomed to growing them properly. Then Freedomcame along, forcing growers to radically review how they grow poinsettias. Now,just when you thought it was safe to grow poinsettias, the floodgates have beenopened. We are currently dealing with a whole slew of new varieties that aredifferent than Freedom. Scheduling, pot sizes, flowering times, height control,rooting out and pinching are just a few of the things growers have to changefor many of these new varieties.

When trialing new varieties, find out if they have the samecrop schedule as Freedom or another variety you know well. Generally, the morevariegated varieties need a longer crop time, as they are slower growers. Knowthe flowering response time of that variety (early-, mid- or late-season). Findout how vigorous the variety is by comparing notes with other growers andpoinsettia trials around the country (See the February 2002 issue of GPN forinformation about this year’s new varieties). Find out as much informationas you can about these new varieties before you plunge ahead and put them intoyour production on a large scale.

4. Scheduling

This is part of not knowing the new varieties. Many growersmake mistakes with their scheduling and blame it on other factors, such asweather, grower problems, too much or too little growth regulator, ortemperature control. To have even a decent chance of producing qualitypoinsettias on time, regardless of pot size, you must have a defined growingschedule for each variety and pot size. This schedule should include sticking,potting, pinching, start of short days (initiation) and shipping. Consult withyour cutting supplier about schedules by variety and pot sizes for your region.

The problems I see growers having with scheduling are notenough time between potting and pinching or between pinching and initiation, aswell as pinching when plants are not rooted properly. The bigger the pot size,the more time is needed between potting and pinching for enough rooting tooccur. Many of the newer varieties are slower-growing than even Freedom andshould have more time between potting and pinching and between pinching andinitiation to get enough vegetative growth to make the desired finished size.Some growers forget that Freedom and a few other varieties initiate earlierthan most varieties, as much as 10 days earlier, except in high-temperatureregions. So they forget to have a different schedule for Freedom compared tothe later varieties, which results in not enough time between pinching andinitiation for Freedom. This results in small plants with fewer leaves on thelaterals. If the grower forces the height taller with temperature, the plantslook very thin. Finally, plants not rooted to the sides of the pot will notbreak properly after pinching, which throws off the schedule.

3. Potting Poor Cuttings

There is an old saying used in the computer industry thatpertains to poinsettias very well: “garbage in, garbage out.” Icannot stress enough the importance of starting with quality poinsettiacuttings, whether you do your own stock or buy cuttings in. If cuttings are toosmall or young, or too big or old, they will not root properly. Maintain yourcutting quality standards throughout and closely inspect your cutting shipmentsfrom suppliers.

The rooting process, whether sticking into a rooting mediaor direct sticking into the finished pot, is the key to getting poinsettias offto a good start. Generally, it will take four weeks to root in a rooting mediasuch as Oasis, and three weeks to root direct-stick. Some varieties may takelonger, and under ideal conditions, most varieties could take only three weeks.Providing the best possible environmental conditions for rooting and practicinggood sanitation are most important to rooting in properly. Rooting temperatureshould be 72-75º F. Keep enough mist on leaves to see beading of waterdroplets, not puddles. Adjust mist by weather conditions, as too much mist willcause diseases and too little mist will cause leaf wilting and delay rooting.Light levels should be around 1,200-1,500 footcandles and can be increased to2,500 before potting. Control Botrytis, Erwinia and Pythium, as well as fungusgnats, in propagation.

When potting rooted cuttings, make sure there are enoughwhite Á roots on the outside of the propagation media. Grade cuttingswhen putting more than one rooted cutting into a finish container. Poor rootson the outside of the rooting media means slower take-off and may result indeath of the plant. If no grading is done on multi-plant containers, you runthe risks of lost plants, variable growth and poor finished quality. Make surewedges are thoroughly wet before planting, and plant them so you cannot see thetop of the wedge. If exposed after the first watering, the wedges will wick outquickly, killing off most of the roots.

2. Height Control

Many poinsettia growers would probably rank height controlas their #1 problem or mistake. But I think height control is actually gettingeasier with the newer varieties. In fact, more growers are keeping plants tooshort by overdoing chemical growth regulators on the newer varieties. Breedersare rolling out new varieties that are slower-growing or more compact, therebyrequiring less growth control. If you can remember growing ‘Annette Hegg’or V-17 varieties, you know what it took to control vigorous varieties. WithFreedom, height control became easier, but you needed to worry about latestretching in the warmer parts of the country. However, with Winter Rose, youneed hardly any growth regulator.

There are several points to remember with height control onpoinsettias: 1) know your varieties; 2) start off with healthy quality cuttingsand good rooting out; 3) use DIF whenever possible, especially in October andNovember; 4) use lower spray rates of B-Nine + Cycocel before initiation, butuse more often if needed; 5) learn how to do late drenches of Bonzi or A-Restto control late stretch; and 6) use graphical tracking software for betterheight control. You can find the poinsettia graphical tracking program onEcke’s Web site ( Each variety and pot size needs its owngraphical track, and keep up with weekly measurements. It is a great way ofevaluating where you are, how well things are working and what needs to be improved.

1. Poor Roots

Getting good roots on finished poinsettias and keeping themcan be easy or hard. Not getting good roots is the main cause of poor-qualitypoinsettias, in my humble opinion. I already covered rooting for cuttings (see#3), but growers must continue to focus on root growth after potting until theyship the plants. If you do not have enough roots, for whatever reason, bymid-October, you are in deep trouble. Because after that time, the plant willfocus more of its energy into the bracts, and root growth slows tremendously.Plus, the environment is usually working against Á you with coolertemperatures and lower light levels. So, you have until early to mid-October toget good roots, then protect them the rest of the way.

The primary causes of poor roots after potting include : 1)planting poor cuttings; 2) keeping pots too wet; 3) wedges exposed on surface;4) poor air porosity in growing media; 5) high salts; 6) fungus gnats; 7)reusing pots without disinfecting them; and 8) Pythium. We already coveredpotting poor cuttings (#3), fungus gnats (#6) and Pythium (#7). Make surerooted cuttings are planted to proper depth so you cover up the rooting mediaand not allow water to wick out and kill off roots. Reusing pots withoutdisinfecting them, along with reusing water saucers without disinfection, isjust a recipe for increasing Pythium.

Poinsettia roots want a media that can hold water but stillprovide enough air for healthy growth. Your media should have 20-25 percent airporosity. Particle size is important to provide air in the media. Make sure youdo not have too many fine peat or bark particles in your mix, or you will holdtoo much water and not enough air. Remember, this crop will be growing a longtime in this media and pot, and compression and degradation of particles canoccur. When this happens, less air porosity is available in the growing media.Keep media moderately moist during rooting out after potting cuttings, but thenencourage roots to go down towards the bottom of the pot by drying downapproximately one third of the way before watering. Do not let poinsettias dryout to wilt, or you will lose roots!

Monitor soluble salts in the media and keep less than 2.5mmhos (SME), especially on dark-green leaf varieties, which need less feed thanlight-green leaf varieties. Also, start dropping the media soluble salts inOctober, and continue through November, cutting off feed altogether about 1-2weeks before shipping. You should finish the crop at 1.0-1.5 mmhos (SME).

I have seen some poinsettia growers salvage their crops whenroots were poor, but they had to jump through a lot of hoops to get there.These crops will also not hold up well in the store or for the consumer. So,get the crops off to a good start with roots, and everything else goes a loteasier.

I’m sure some growers could add a few more mistakes tomy Top 10 List. Drop me a note so I can continue to expand this list. Justremember, growing poinsettias is supposed to be fun! So, have a great time thisyear, and may all of your poinsettias turn out beautifully.

Roger C. Styer

Dr. Roger C. Styer is president of Styer’s Horticultural Consulting, Inc., Batavia, Ill. He can be reached by phone at (630) 208-0542 or E-mail at [email protected]

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