1. Greenhouse Management and Crops
Section 4
Unit 13, 14, 15

2. Poinsettias
Unit 13

3. History
Poinsettias were grown in Southern California as cut flowers in 1900
Today, growing poinsettias is a big part of many horticultural operations

4. Greenhouse management
Factors to consider in greenhouse production are…
Temperature
Moisture
Ventilation
Climate

5. Temperature Important to growing a successful crop
Day temp. should be 5-10 degrees higher than night temp.
Thermometers should be at the plant level, out of direct sunlight to ensure optimum growth

6. Moisture Plant growth is dependent on moisture
Influences relative humidity
Amount of water needed depends on the type of plant and the outside conditions on a particular day
Appearance and feel of the medium is an indication for watering plants

7. Ventilations Movement and exchange of air in the greenhouse
Should be able to feel the air movement in the greenhouse
Ensures correct temp and relative humidity
Helps control plant diseases

8. Climate
Directly influences the type of greenhouse structure, heating and cooling systems

9. Poinsettia Flower
Small, yellow flower that grows at the terminal end of the plant
Just below the flower are the bracts
Leaves that give the poinsettias their color
Most common color is red
Require a short day for the production of the flower
Should be grown in full sunlight
During months w/ long days, the plants develop leaves and increase stem length

10. Growing Poinsettias Start from a 2 ¼” rooted poinsettia cutting
Be sure the plant is healthy
Plant in pots 4”, 5”, 6” 7” 8” or 10”
Night temp should be 65 degrees
Day temp should be 70 – 75 degrees

11. Pinching Process of removing the terminal end of the plant
Accomplished by taking the top of the plant between the thumb and index finger and carefully breaking the top of the poinsettia completely off
4-5 leaves should remain on the plant
After pinching, new shoots called breaks will develop from the bud in the axis of the node
Each shoot will produce a flower
Main reason for pinching is to increase the number of bracts per plant

12. Soil Mixes May be grown in many different media
Must be porous and well-drained
Should be free of insects and disease organisms
Should have good nutrient-holding capabilities
Soil can be sterilized at 180 degrees for 30 minutes

13. Fertility Fertilizer should be complete
Contain nitrogen, phosphorus, and potassium
Follow manufacturer’s recommendations for application

14. Growth regulators Growth regulators have 2 main purposes
Control the height of the plant
Improve quality of color in bracts
Applied as a soil drench or foliar spray
Examples:
Cycocel
Ancymidol
Bonzi
B-nine

15. Height can be controlled to some extent by adjusting light level and durations and by regulating day and night temps
Brighter light results in more compact plants
Shorten plants by lower daytime than nighttime temp

16. Maintaining Poinsettias
Handle new plants carefully
Protect from insects using chemical pesticides
Protect from attack by disease organisms
Clean poinsettias must be purchased
Clean growing media must be used
Treat w/ fungicide when transplanted

17. Chrysanthemums
Unit 14

18. Chrysanthemums The most popular cut flower sold in the US
Because of artificial control of day and night in the greenhouse, they can be grown throughout the entire year
Most popular on Mother’s Day, Easter, and Memorial Day

19. Determining market and variety
Schedule planting so that plants bloom at desired time
Some varieties bloom in 8 weeks after the start of short days, others 10, 12, or 14 weeks
This is known as response time
Chrysanthemums are cataloged by their response time

20. Regulating Light Mums are a short-season crop Control light when…
Sets flower buds and blooms only when nights are long and days are short
Control light when…
Rooted cuttings are 1st potted – days kept long and nights short (7 hrs of darkness max)
Summer flowering is desired, days kept short and nights long to encourage proper timing of flower bud formation

21. Obtaining Starter Plants
Propagated by softwood cuttings
Diseases may be passed along from parent plants
Very important to purchase rooted cuttings from disease free retailers

22. Establishing a growing schedule
A growing schedule must be established before ordering rooted cuttings
Start at the end of the schedule (the blooming date)
Control day and night lengths to follow the schedule

23. Planted rooted cuttings
6-inch plastic pot is a good choice for planting rooted mum cuttings
Requires 5 cuttings per pot
Well drained medium that holds moisture well
Water added to the medium should quickly drain to the bottom of the pot
Don’t let the potted cuttings dry out
Provide a constantly moist, but not wet soil
Add water when the top of the potting medium 1st appears to be drying out

24. Caring for Potted Cuttings
Greenhouse temp should 63 degrees at night when 1st placed in the growing area
Higher temps promote faster vegetative growth
If temp drops below 60 degrees flower buds may not set evenly
Temps are dropped to 62 degrees and then to 55 degrees for the last 3 weeks
Cooler temp tends to harden off the plants

25. Fertilizing cuttings Constant application of fertilizer
Diluted fertilizer may be added to the irrigation water
Slow release fertilization
Mixed in the potting medium at the time of planting
Timed applications
Apply once every 2-3 weeks in irrigation or to the pot as needed

26. Watering
Frequency varies w/ temperature and humidity and water holding capacity of the medium
Hot & Dry weather, twice a day
Other times, once a day or every other day
Check soil frequently and add water whenever top of medium is beginning to appear dry
Do not keep soil saturated

27. Pinching and Disbudding
Pinch off ¼ to ½” of stem growth
Causes shoots to develop resulting in more branches
Ideal mum should have about flowers per pot

28. Controlling insects and disease
Growth Retardants
Similar to Poinsettias
Controlling insects and disease
Good sanitation and cultural practices often all the control needed