KiO MASS. EXPERIMENT STATION BULLETIN 277 



Summary 



An investigation has been made of the effect of flower pot composition 

 on plant growth. Flower pots are either porous or non-porous. This character 

 of porosity in any pot determines the cultural practice to be followed for 

 good growtii. The porous pot, because of its evaporating surface, allows the 

 soil to dry out unless a means is provided for the pot itself to take up 

 moisture from some outside source. The porous pot, when dry, can adsorb 

 one-half the normal daily application of water given to 3, 4, 5, and 6-inch 

 sizes, and one-third tlie amount given to a 7-inch pot. The evaporation of 

 moisture from the outside surface of the pot has a cooling effect on tiie soil; 

 hut this cooling of the soil has no effect on plant growth. About twice as 

 Huich water is lost from a porous pot by evaporation as from a non-porous 

 pot in the same period of time. 



The relative humidity of houses and offices is so low during the heating 

 months of the year that the evaporating power of the air frequently dries out 

 the loMer half of the mass of soil in a clay or porous pot. The roots in this 

 section, therefore, are killed, weakening the plant so that it gradually dies. 

 The moisture deficit caused by the excessive evaporation is seldom made up 

 by the daily watering of plants. 



Paper pots, properly protected from the activities of micro-organisms, 

 will produce as good growth as can be obtained in glass or clay pots. How- 

 ever, if decomposition is in progress, the organisms make use of the available 

 nitrogen in the soil and the plant suffers from nitrogen starvation. This 

 nitrogen deficiency may be overcome by the addition of available nitrogen to 

 the soil in excess of what can be utilized by the micro-organisms. 



The method of testing, with a variety of materials for water-proofing 

 paper fibers, is described. Better growth was obtained by the use of a disc 

 in tiie bottom of the paper pot used in the experiments. This disc served to 

 prevent the leaching of nutrients and also aided in the retention of the root 

 system within the jiot. 



The most practical paper pot was one in wliicli the fillers were impreg- 

 nated and bound together witii asphalt. These paper pots produced plants 

 e(pial to tiiose grown in glass and clay pots. 



Glass containers may be used successfully for j)lants. With a glass pot, 

 or any non-porous pot, care nuist be taken not to over-water the soil. Com- 

 pared with the watering of porous pots, the frequency for watering a non- 

 porous pot may be cut in half. There should be more soil in a non-porous 

 pot than in a porous pot to prevent excessive applications of water. Glass 

 containers are j^articularly valuable for the home and office, or in atmospiieres 

 with a low humidity. They conserve the moisture, whicii is evenly distributed 

 in the soil of the container. 



Rubber flower pots represent a type of non-porous pot moulded from a, 

 synthetic sul)stance. These pots jiroduced good plants and are more perma- 

 nent and less breakable than glass or clay ])ots. 



