Top 10 Poinsettia Mistakes

July 9, 2002 - 10:16

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

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

10. Stem Breakage

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

Stem breakage can be due to several factors: 1) choice of
varieties; 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 many
laterals; 6) bracts too big and heavy; and 7) pushing plants with late
temperature to make height.

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

9. Botrytis

This disease presents problems during propagation and again
during bract development and shipping. Symptoms during propagation include
brownish 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 is
used. During bract development, Botrytis can develop as little dark spots and
spread 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 areas
clean of dead and dying tissue or plants. Wean cuttings off mist as soon as
possible. Give the cuttings enough space in Á propagation so leaves are
not covered up, providing more food for Botrytis. Watch your mist cycles
closely at night and during cloudy days. For fungicide sprays, use Daconil,
Chipco 26GT (or 26019), Medallion, Phyton or Decree at least weekly during
propagation, starting about three days after sticking. Apply at end of mist cycle
for the day during the early stages.

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

8. Bract Expansion

Failure to properly expand bracts by ship date is usually a
problem with mid- to late-season varieties. This is due to early varieties
being grown with the later varieties in the same greenhouse zone. Once the early
varieties fully expand, temperatures are usually dropped to help hold them, not
realizing that the later varieties need a warmer temperature to fully develop
bracts. Best bract expansion is achieved with 68º F average daily
temperature (ADT). Holding Freedom varieties requires 60-65º F, well below
the bract expansion temperature. Group mid- and late-season varieties
separately from early-season varieties, or pay closer attention to how much you
lower the temperatures.

Another reason bracts may not expand enough is too much
growth regulator. Constant late use of Cycocel can reduce bract size. But the
main culprit in the United States is usually Bonzi sprayed too late or Bonzi
drench applied too early. Cut-off dates for Bonzi sprays are early to
mid-October in the Deep South and initiation in the North. For Bonzi drenches
after initiation dates, wait until plants are about one inch from saleable size
and have about 20 percent color showing. Drenching before this date will cause
delay in bract expansion. For Freedom, this means the late Bonzi drench is
usually 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 shows
mainly at the root tips and works upwards through the roots, collapsing plants
even 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 factors
that hinder roots: 1) too wet, 2) high salts, 3) poor air porosity in media and
4) low calcium. Use a well-drained media consisting of some larger particles
for 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 around
roots. Incorporate calcium into your feed program. On Winter Rose varieties,
set up the irrigation on a different schedule, as this variety does not dry out
as fast. Fungicide drenches applied monthly will help. Use Banrot, Subdue,
Truban or Terrazole, making sure to combine another fungicide for Rhizoctonia
with Subdue, Truban or Terrazole. Many growers are also finding good results
incorporating a biofungicide into the media soon after potting, such as
Rootshield, Companion or Actinovate, and then drenching with fungicides as
needed later in the crop.

6. Fungus Gnats

This pesky little insect causes lots of headaches for
poinsettia 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 antennae
and lazy flying pattern. The larvae have a black head capsule and feed on
decaying organic matter, including roots. Once you can get past the rooting out
stages and into a normal wet/dry cycle, fungus gnats are not as much of a
problem.

For control, make sure to properly clean propagation and
growing areas before poinsettia season starts. Knock down any adults with
autofogs or sprays, and treat the dirt floors and drainage areas with a sprench
for larvae (see Figure 1, Á below left). Get sticky cards up in your
poinsettia areas to tell you when you have problems and how well your control
program is working. In propagation, use Gnatrol, Distance (sprench rate),
Citation, Ornazin or Azatin, or Enstar II. Duraguard and Knox-Out will not work
well when media is wet all of the time, so save them for later. Adept is no
longer labeled for poinsettias, but you can use it on the floor. Nemasys
(nematodes) will not work well in Oasis wedges but works much better in
direct-stick production. Save the Marathon for whiteflies. Hypoaspis mites will
work well in conjunction with insect growth regulators, but they do not like to
swim. You can broadcast them over pots once they’re off of mist and
before plants grow very big and are spaced. They will scavenge across the media
surface and feed on fungus gnats and shorefly larvae, and any thrips that are
in the soil.

5. Not Knowing the Varieties

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

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

4. Scheduling

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

The problems I see growers having with scheduling are not
enough time between potting and pinching or between pinching and initiation, as
well 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 to
occur. Many of the newer varieties are slower-growing than even Freedom and
should have more time between potting and pinching and between pinching and
initiation to get enough vegetative growth to make the desired finished size.
Some growers forget that Freedom and a few other varieties initiate earlier
than most varieties, as much as 10 days earlier, except in high-temperature
regions. So they forget to have a different schedule for Freedom compared to
the later varieties, which results in not enough time between pinching and
initiation for Freedom. This results in small plants with fewer leaves on the
laterals. If the grower forces the height taller with temperature, the plants
look very thin. Finally, plants not rooted to the sides of the pot will not
break properly after pinching, which throws off the schedule.

3. Potting Poor Cuttings

There is an old saying used in the computer industry that
pertains to poinsettias very well: “garbage in, garbage out.” I
cannot stress enough the importance of starting with quality poinsettia
cuttings, whether you do your own stock or buy cuttings in. If cuttings are too
small or young, or too big or old, they will not root properly. Maintain your
cutting quality standards throughout and closely inspect your cutting shipments
from suppliers.

The rooting process, whether sticking into a rooting media
or direct sticking into the finished pot, is the key to getting poinsettias off
to a good start. Generally, it will take four weeks to root in a rooting media
such as Oasis, and three weeks to root direct-stick. Some varieties may take
longer, and under ideal conditions, most varieties could take only three weeks.
Providing the best possible environmental conditions for rooting and practicing
good sanitation are most important to rooting in properly. Rooting temperature
should be 72-75º F. Keep enough mist on leaves to see beading of water
droplets, not puddles. Adjust mist by weather conditions, as too much mist will
cause 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 to
2,500 before potting. Control Botrytis, Erwinia and Pythium, as well as fungus
gnats, in propagation.

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

2. Height Control

Many poinsettia growers would probably rank height control
as their #1 problem or mistake. But I think height control is actually getting
easier with the newer varieties. In fact, more growers are keeping plants too
short by overdoing chemical growth regulators on the newer varieties. Breeders
are rolling out new varieties that are slower-growing or more compact, thereby
requiring less growth control. If you can remember growing ‘Annette Hegg’
or V-17 varieties, you know what it took to control vigorous varieties. With
Freedom, height control became easier, but you needed to worry about late
stretching in the warmer parts of the country. However, with Winter Rose, you
need hardly any growth regulator.

There are several points to remember with height control on
poinsettias: 1) know your varieties; 2) start off with healthy quality cuttings
and good rooting out; 3) use DIF whenever possible, especially in October and
November; 4) use lower spray rates of B-Nine + Cycocel before initiation, but
use more often if needed; 5) learn how to do late drenches of Bonzi or A-Rest
to control late stretch; and 6) use graphical tracking software for better
height control. You can find the poinsettia graphical tracking program on
Ecke’s Web site (www.ecke.com). Each variety and pot size needs its own
graphical track, and keep up with weekly measurements. It is a great way of
evaluating 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 them
can be easy or hard. Not getting good roots is the main cause of poor-quality
poinsettias, in my humble opinion. I already covered rooting for cuttings (see
#3), but growers must continue to focus on root growth after potting until they
ship the plants. If you do not have enough roots, for whatever reason, by
mid-October, you are in deep trouble. Because after that time, the plant will
focus more of its energy into the bracts, and root growth slows tremendously.
Plus, the environment is usually working against Á you with cooler
temperatures and lower light levels. So, you have until early to mid-October to
get 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 covered
potting poor cuttings (#3), fungus gnats (#6) and Pythium (#7). Make sure
rooted cuttings are planted to proper depth so you cover up the rooting media
and not allow water to wick out and kill off roots. Reusing pots without
disinfecting them, along with reusing water saucers without disinfection, is
just a recipe for increasing Pythium.

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

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

I have seen some poinsettia growers salvage their crops when
roots 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 lot
easier.

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

About The Author

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 carleton@voyager.net.

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