Environmental Requirements for Plant Growth Unit 4 Introductory Horticulture

Light  Intensity: Brightness. Foot-candle is the form of measurement  Day-length or Photoperiod: time in light  Long day: summer annuals (marigolds)  Short day: short photoperiods (poinsettia)  Color: red spectrum -> blue spectrum plants need both, sun has both

Temperature  Varies from plant to plant  Sun lovers can take high temps with plenty of water and humidity  Greenhouse temp  Germination o F  Growth o F

Water  Necessary for 13 of 16 nutrient uptake  Growth and Maintenance  Photosynthesis  Sap – transport nutrients  Transpiration – cooling  Turgor – plant shape due to cell shape, opposite of turgor is wilt

Water (continued)  Methods and Frequency  Infrequent, thorough watering is best  Container plants: bottom watering is best  Encourages root growth  Dry soil helps reduce disease

Humidity  40-60% is ideal  Cold winter days and hot summer days humidity is too low  Plant misters can be used

Media  Soil (natural media), Artificial, Hydroponics (no media)  Support the plant  Consistency of volume – wet or dry  Adequate porosity (drainage, aeration)  Provide nutrients (13 needed from soil)  Correct pH for plant (most plants 6.5-7)

Nutrients  Plants need 16 nutrients  Organic macro nutrients  Carbon, hydrogen, oxygen  Essential nutrients  Nitrogen  Phosphorus  Potassium

Sterilization (Applies to Media)  Free of disease, weed seeds, parasites, insects  180 o F for 30 minutes – steam dry heat  Chemical sterilization – methyl bromide gas  Steam heat – commercial greenhouse  Chemical – commercial greenhouse

Insects and Diseases  Sources and Prevention  Media: sterilize  Infected Plants: buy good quality plants from reputable greenhouses  Watering: bottom watering whenever possible, avoid splashing  Controls  Insects: spray, dip, discard  Weeds: pull, spray  Disease: discard