Greenhouse Management and Crops

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 • 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 be @ 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 10-15 flowers per pot

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