Requirements for Plant Growth Plants require certain environment for optimum growth In greenhouse one must maintain best environment for growth

Plant Media Soil –Sand –Silt –Clay –Organic Matter

Water 1. Gravitational Water (held by gravity) –Drains away –Soils with large pores lose water fastest

Water 2. Capillary Water –Held against gravity in pores –Held in thin film around particles –Soil particles are electrically charged

Planting Media Mixes Advantages to soil less media –1. Mix is uniform –2. Sterile –3. Lighter in weight –4. Good moisture retention and drainage

Planting Media Mixes Disadvantages to soil less media –1. Lightweight –2. Minerals missing must be added –3. Hard to transplant into soil

Planting Media Mixes Content of mixes –Perlite: volcanic origin Improves aeration Small white pebbles

Media contents –Vermiculite: yellow expanded mineral Increases moisture holding capacity

Media Contents Sphagnum Moss: acid bog plants –Holds moisture, very light Peat Moss: decomposed vegetation –Holds moisture

Media Contents Tree Bark –Improves aeration

Plant Food Water: most important –Plant weight = 90% water –1% of water absorbed is used, rest is lost through leaves

Plant Food Water: –Transpiration: Water lost through stems and leaves Natural air conditioning

Plant Food Major Nutrients –N, P, K –Numbers in fertilizer are those three in order so… = 10% N, 15% P, and 20% K

Plant Food Nitrogen –Makes dark green color –Too much is a problem Lowers disease resistance Weakens stem –“leaching” is a problem

Plant Food Phosphorus –Affects maturity –Cell division –Roots –Insufficient = purplish color on underside of leaves

Plant Food Potassium –Affects Photosynthesis –Root System –Insufficient = also purplish color, much more rare than P

Soil Acidity = acidic 14= basic 7 neutral Acid = add lime Basic = add sulfur

Other Factors Temperature F Light Short and Long Day Plants Plant Diseases –Biggest scares to greenhouses Insects our biggest problem Gases