Horticulture 2 poinsettias
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Everything You Always Wanted to Know about Poinse9as* * But were afraid to ask…
description
Classroom lecture on poinsettia crops
Transcript of Horticulture 2 poinsettias
Everything You Always Wanted to Know about Poinse9as*
* But were afraid to ask…
What you NEED TO KNOW about poinse5a flowering:
• Poinse9as ini?ate flowers when days become shorter than nights. In the Northern Hemisphere, this day length condi?on naturally occurs during mid to late September.
• Once short days begin, it is important that nights con?nue to get longer for bracts to form color. During this development stage of the poinse9a, if nights get shorter rather than longer the flowering will be disrupted and plants will fail to flower.
• The phase of growth prior to flower ini?a?on is referred to as vegeta?ve growth, while the flowering stage is known as the reproduc?ve phase.
• The flowering response ?me is the ?me, usually in weeks, required for the plant to develop to a mature, salable flowering plant from the date of flower ini?a?on. This assumes all growing condi?ons are “normal” for the crop.
Poinse9a Crop Scheduling
• Schedule flowering response ?me for op?mum development.
• Start with the desired flower maturity date (Dec. 1) and work backwards using the flowering response ?me (for these cul?vars, 8 and 8.5 weeks) to determine when the crop needs to ini?ate flower in order to be ready for sale at the appropriate ?me.
Vegeta?ve Growth Requirements
Vegeta?ve Growth Requirements: Calculate vegeta?ve growth requirements based on the finished height and flower ini?a?on dates. In order to calculate vegeta?ve growth requirements the grower must be aware of when a cul?var ini?ates flowers so that pinching can be scheduled accordingly. A properly scheduled pinch assures plants will have enough ?me between pinch and flower ini?a?on to form enough leaves to achieve the desired finished height. Reduced ?me between pinch and flower ini?a?on will result in shorter plants.
Pinching • The ?me needed for vegeta?ve growth
is based on desired size, geographic loca?on, and vigor of each cul?var.
• Each cul?var has a different natural growth poten?al so more or less ?me between pinch and flower ini?a?on is required based on natural vigor.
• Plants in larger pots require more ?me between pinch and flower ini?a?on.
Geographic loca?on is also important because naturally higher light and warmer temperatures will result in more vegeta?ve growth. Growers in southern climates will find that less ?me is necessary between pinch and flower ini?a?on to achieve adequate size while growers in northern climates will find that more ?me is required. The charts provided (Table 2) suggest the produc?on ?me for various forms based on loca?on.
How to Pinch Poinse9as
Understanding Photoperiodic Response
Poinse5as are classified as short-‐day (long-‐night) plants that ini?ate flowers when the day length is reduced to a cri?cal amount of ?me, 12 hours and 20 minutes. This occurs around September 20 to 25, during the fall equinox. Photoperiod Manipula?on Requirements: If the desired cul?var’s natural finish date based on flower ini?a?on date and response ?me do not match with desired finish dates then photoperiod manipula?on must be used. To force earlier finish, black clothing must be used to ini?ate flowers early. Determine black cloth start ?me by subtrac?ng response in weeks from the desired finish date (Dec. 1 – about 8 weeks for our cul?vars). h^p://www.greenhousegrower.com/video/plant-‐culture/v-‐understanding-‐photoperiodic-‐response/ Ligh?ng and Photoperiod: Light intensity for growing quality poinse9as should be 3,500 to 4,500 fc for cul?vars with dark green foliage and 5,000 to 6,000 fc for cul?vars with medium green foliage. We will add ligh?ng from about Sept. 11 to Sept. 30. Shade cloth is generally required in the south for reducing greenhouse temperatures. A 30-‐40% shade cloth can be used un?l October 1 without affec?ng plant quality. If possible, reduce light intensity to 2,000 fc aher primary bracts are fully colored and secondary bracts are almost mature to prevent fading.
Ligh?ng and Black Cloth • Some cul?vars ini?ate flowering prior to the cri?cal day lengths and
should be lighted with night ligh?ng. (We will not need to do this.)
• If the schedule for a cul?var requires the start of short days before those naturally occurring, pull black cloth over the plants from 5 p.m. to 8 a.m. at the appropriate ?me of year, depending on the cul?var and geographic loca?on.
• 14-‐hour nights should be provided using black cloth. We will be doing this from about Oct. 6 un?l about Nov. 5.
• For later finishing, ligh?ng to extend the day length is used to delay flower ini?a?on.
Our Schedule • We will add ligh?ng from about Sept. 11 to Sept. 30.
• 14-‐hour nights should be provided using black cloth. We will be doing this from about Oct. 6 un?l about Nov. 5 or so, from 5:00 p.m. to 8:30 a.m.
Sept. 3 Sept. 22 9/3: Add shade cloth; add fer?lizer when watering.
Add ligh?ng 9/11 to 9/30
Oct. 6-‐Nov.11 Dec. 8
Pinch Black cloth Taper off fer?lizer
Dec. 1
• Add shade cloth on Sept. 3; add ligh?ng from about 9/11-‐9/30 • Add 15-‐5-‐15 fer?lizer when watering: 3.38 oz. (98.52 g) conc./gal. water for 1:16 Hozon • Pinch on Sept. 22 • Black cloth starts about Oct. 6 un?l Nov. 5 • Be vigilant! Look for any signs of stress, pests (whitefly), and diseases • Sale date around Dec. 8
Poinse5a Schedule -‐ Es?mated
Growing Guidelines
Vegeta?ve Growth Requirements based on geographic loca?on
Vegeta?ve Growth Adjustments Based on Vigor
Establishing Requirements for Various Sizes
Poinse9a Temperatures
v November-‐ Drop night temperatures to 55-‐ 60°F (12-‐16°C). Do not drop temperatures below 55°F (12°C). Flower development will not progress below 50°F (10°C) and chilling injury may occur.
v On sunny days allow the greenhouse to warm to 75-‐80°F (24-‐26°C) to offset cold nights. On cloudy days maintain 75°F (24°C). The goal is to achieve an average daily temperature of 65°F(18°C).
v Mid November to December-‐ Plants are mature and ready to ship.
• Media for growing poinse9as should be on the coarse side and excep?onally well-‐drained.
• The pH should be 5.8-‐6.4. • Poinse9as are more suscep?ble to
calcium and magnesium deficiencies than many plants; therefore, we are using a fer?lizer with 5% Mg and 2% Ca, as well as micronutrients, added.
• FAFARD MIX NO. 3-‐B is an excellent, general purpose mix containing peat moss, perlite, vermiculite and about one fourth processed bark. It is recommended for flowering plants, bedding plants, hanging baskets, foliage plants and interiorscape use. This is the preferred Fafard mix for flowering plants.
A dependable source of high quality water is an important considera?on in growing poinse9as. The alkalinity of the water should not be so high as to drive the pH of the medium above 6.5 or micronutrient deficiencies can occur. The total soluble salts and presence of nutrients or toxins should also be known. Poinse5as can be watered overhead during early stages of produc?on but moisture on the bracts is highly undesirable.
Water
Therefore, it is recommended that crops be placed on an automa?c watering system at or soon aher spacing. We, however, have other plants with different fer?lizer needs on that system, so we will need to hand water and use the Hozon siphoner.
Fer?liza?on • Poinse9as are generally heavy feeders, especially during early produc?on.
Fer?liza?on should begin as soon ader po5ng as possible depending on how much starter nutri?on has been added to the medium.
• Fer?lity programs vary widely and may include liquid fer?liza?on or liquid in combina?on with slow release fer?lizers. However, success depends on raising the ini?al fer?lity quickly, then tapering-‐off toward the finish of the crop.
• We will be using a 15-‐5-‐15 (N-‐P-‐K) fer?lizer at 300 ppm to start. N-‐P-‐K is the elemental shorthand for the three major nutrients in fer?lizers. “N” stands for Nitrogen, “P” stands for Phosphate (P2O2) and “K” stands for Potash (K2O).
15-‐5-‐15 Cal-‐Mag Fer?lizer
High nitrate and
low phosphate with added calcium and
magnesium
We’ll start with 300 ppm (parts per million). That’s 4.1 oz. Cal-‐Mag/gal. of concentrate with a 1:16 Hozon siphoner.
Our fer?lizer program: • 15-‐5-‐15 at 300 ppm N (4.1 oz/gal. with 1:16 Hozon
siphoner) for first 4-‐5 waterings. Drop to 200-‐250 ppm N (3 oz./gal. concentrate) aher 5th watering.
• Drop to 100-‐150 ppm N N (1.7 oz/gal. with 1:16 Hozon siphoner) in November.
• Test and chart pH and soluble salts at least every two weeks.
• Reduce nutri?on in the last few weeks of the crop. In November and December, temperatures and light intensity are dropping and the needs of the plant decrease as flowers develop.
• Many growers will stop fer?lizing completely in late November. Shelf life of poinse9as is increased if the media soluble salts is close to zero at shipping (or sale) ?me.
Spacing Poinse9a plants are ohen maintained on benches, pot-‐to-‐pot aher po9ng and up to the ?me of pinch for easy maintenance and to make the pinching task easier. However, they should be placed at the final spacing soon aher pinching and before plants begin to crowd. This increases the light intercep?on by the plants and decreases the need for growth retardant. Final Spacing for Pinched Plants Pot size Cu9ngs/pot Spacing (") Sq.h./pot 6 2 15 x 15 1.5 4 1 8 x 9 .5
Pres?ge Red from Rooted Cu9ngs
Finished Poinse5as
