August 2019 - 29

RESEARCH
Figure 2. Weekly crop photos like these taken by Steffi Hugo at American Farms in southwest Florida are an excellent way to compare if your color is on track
compared with past years. From left to right photos taken on Sept. 29, Oct. 19, Oct. 26, Nov. 3 and Nov. 9.
either of these conditions occur in the month after short days begin. The
risk continues to increase as temperatures increase above an ADT of 75° F
or a NT of 73° F during this flower initiation period. Some heat delay may
therefore occur even if your temperatures are not as extreme as those in
Table 1.
STRATEGIES TO MANAGE HEAT DELAY RISK
* Select varieties that are fairly resistant to heat delay. Ask your
breeder supplier for their recommendations, which for southern
areas include:
→ 'Christmas Beauty Red', 'Christmas Joy Red', 'Christmas Magic',
'Christmas Spirit' and 'Christmas Wish' (Ball/Selecta)
→ 'Aries', 'Astro' and 'Robyn' (Beekenkamp)
→ 'Advent', 'Ferrara', 'Premium Red', 'Red Soul' and 'Tikal'
(Dümmen Orange)
→ 'Aria Red', 'Orion Early Red', 'Majoris Red', 'Mars Early Red'
and 'Orion Red' (Syngenta Flowers)
* Keep good records each year for each variety in your greenhouse,
especially recording the date of first bract color (usually ≈4 weeks
after start of short days), visible flower bud (≈5 weeks), and
shippable plant (≈7 to 10 weeks) for each of your varieties.
* Take weekly photos of your crop from late September onward to
have a visual reference for subsequent years (Figure 2).
* Track temperatures inside your greenhouse, especially during
September. If possible, cool the greenhouse to have an ADT below
80° F and NT below 74° F. If you have a week or more of high
temperatures during this period, start planning ahead for possible
shipping delays.
* If heat delay has occurred in September and October, keep
temperatures warm (75° F ADT and NT at <73° F) during the bract
and flower development period from mid-October through November
to help flowers develop as quickly as possible.
* Consider growing poinsettias under black cloth to provider
longer night lengths (14 hours) than those that occur naturally
in September and October. Poinsettias will be less susceptible to
heat delay when grown under longer night lengths provided that
temperatures under the curtains are not excessive.
With increasing variability in fall weather, reduce the risk of heat delay
by following breeder recommendations for varieties that have reduced
heat sensitivity and grow well in your area. By keeping a close eye on
crop development and temperature during September, you can evaluate
the risk of delayed shipments from heat delay.
Acknowledgements: We thank Ball/Selecta, Beekenkamp, Dümmen
Orange, Syngenta Flowers, and industry partners in the Floriculture
Research Alliance (www.floriculturealliance.org) for supporting poinsettia
trials at University of Florida.
Paul Fisher is a professor and Extension specialist at University of Florida
(pfisher@ufl.edu), Jim Faust is associate professor (jfaust@clemson.edu) and
Michael Tierney (tierne2@g.clemson.edu) is an MS student at Clemson University.
HIGH-DENSITY LINERS
™
What's the biggest benefit to the High-Density Liners at Pleasant View Gardens? Is it the lower freight costs?
Is it the huge number of varieties? Is it both?
This program gives you the largest menu of plant material and genera around. From herbs and vegetables, to
grasses, annuals, and perennials. They come in 128- and 64-cell configurations. Compared to a standard 105
tray, you get more varieties within the same footprint (twice as many with our half-trays), while reducing your
per-plug freight cost by nearly 25%.
More varieities. Less Freight. What more could you want?
Pleasant View Gardens, Inc. » 603-435-8361 » pwpvg.com

http://www.floriculturealliance.org http://www.pwpvg.com

August 2019

Table of Contents for the Digital Edition of August 2019