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 manufacturers 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 Mothers 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
• Dont 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 _at_ 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