Richard T. Poole’s research while affiliated with Florida Clinical Research Center and other places

IntroductionThe Essential ElementsFactors Affecting Frequency and Quantity of Fertilizer ApplicationNutrition and Fertilization of Specific CropsLiterature Cited

IntroductionBiological PrinciplesCultural and Environmental Factors Affecting AcclimatizationShipping ProceduresPostharvest Handling in InteriorsConcluding Remarks

Dieffenbachia ‘Camille’ liners were planted and grown until “ready-for-market” in 1.6 liter pots containing Vergro Container Mix A without superphosphate. Plants were fertilized (FR) using 4, 8, 12, or 16 g 19N-2.6P-10K (0.14, 0.28, 0.42 or 0.56 oz 19–6–12) Osmocote 3-month release formula and were irrigated (IF) one, two or three times per week. Experiments were conducted during cooler months (20 weeks, January–May) and also during warmer months (13 weeks, June–September). Medium leachate samples were collected weekly for the duration of each experiment. Plant grade and top fresh weight (growth parameters) during the winter responded to an interaction between treatments (FR × IF). During the summer experiment, growth parameters were affected only by IF and were greatest at 3 irrigations per week. Weekly leachate characteristics (pH and electrical conductivity [EC], and P, NH4-N and NOx-N content) were affected only by FR, with increased fertilizer generally resulting in leachate with decreased pH and increased EC and increased P, NH4-N and NOx-N concentrations, in both winter and summer with the exceptions during the winter of P which increased with either an increase in FR or IF and of NOx-N which also increased with increased IF. Interaction occurred between FR and IF for total mg P leached during each experiment and for total mg NOx-N leached during the 20 week experiment, while total mg NOx-N leached during the 13 week experiment and total mg NH4-N leached in each experiment were affected only by FR.

Codiaeum variegatum (L.) Blume `Petra' liners were transplanted into 15-cm pots and fertilized using 24N-3.4P-14.2K at a total of either 7.2 or 14.4 g N/pot over a 26-week growing period. Eight fertilizer treatments followed four application schedules at a low and high (double the low) rate. Schedules attempted to maximize fertilizer utilization with applications based on projected plant growth patterns. Irrigation was on an as-needed basis, and all leachate was collected from each pot. Weekly leachate per pot was analyzed for pH, electrical conductivity (EC), and NH 4 -N and NO x -N content. Plant and color grades, and height change were recorded and elemental tissue analyses done for each plant at experiment termination. Fertilizer rate and schedule affected height change, and pH and EC, as expected. Total mg NH 4 -N and NO x -N in the leachate increased with increased fertilizer rate. Fertilizer application schedule affected NH 4 -N content at the high fertilizer rate and NO x -N in the leachate at both fertilizer rates with the optimizing curve treatments leaching the least NO x -N for their respective fertilizer rates. Total mg N/pot (mg NH 4 -N + mg NO x -N) was significant for both fertilizer rate and schedule.

Nitrogen leaching into surficial aquifers continues to become more of a problem in several areas of the U.S., and thus potential for regulation of foliage plant producers is increasing. A factorial experiment evaluated liquid and controlled-release fertilizer sources at three irrigation levels [100, 200, or 300 ml (3.4, 6.8, or 10.2 oz) per 15 cm (6 in) pot twice weekly] for NH4-N, NO3-N, and P in leachate. Samples were collected weekly for 12 weeks beginning the last week of September. Plant grade and top fresh weights were similar for all treatments, but large variations occurred in NH4-N, NO3-N, and P levels in leachate due to irrigation level. Increasing irrigation level above 100 ml (3.4 oz) twice weekly resulted in increases of NO3-N present in leachate, with levels as high as 126 mg/pot observed toward the end of November. NH4-N levels were affected by irrigation during the first seven weeks of the experiment but, after week 2, were lower than one mg/pot. Phosphorus levels ranged from 0.9 to 5.7 mg/pot in leachate with responses to irrigation treatment throughout the experiment.

Three minimum air temperatures (AT), 15.5°, 18.5°, and 21°C (60°, 65°, and 70°F), four constant soil temperatures (ST), 15.5°, 21°, 26.5°, and 32°C (60°, 70°, 80°, and 90°F), and three fertilizer rates (FR) 2.5, 4.2, and 5.9 g 19N-2.6P-10K (0.09, 0.15, and 0.21 oz 19-6-12) Osmocote/15 cm (6 in) pot/3 months were utilized on Epipremnum aureum ‘Golden Pothos’ during November–April in 1983–84, 1984–85, and 1985–86. Data collected included plant grade, leaf color grade, top fresh weight, root fresh weight and leaf surface area. Analyzed data were similar for all three experiments with AT × ST interactions significant for 4 of 5 measurements in 1984 and 1985 and for all 5 measurements in 1986. In general, as fertilizer rate increased, all measurements increased linearly with only root fresh weight not increasing significantly. Results from the 1986 experiment are used for discussion.

Three species of foliage plants were produced with three media, in an ebb and flow irrigation system (experiments 1 and 3) or with overhead manual irrigation (experiments 2 and 4). Expt. 1 used a constant feed program of 24N-3.5P-13K (24-8-16) soluble fertilizer added to the water supply at rates of 0.21, 0.42, 0.63 or 0.84 g/L. In experiments 2, 3 and 4, plants were fertilized with a constant feed program using the soluble fertilizer at 0.63 g/L or with a 19N-2.6P-10K (19-6-12) slow release fertilizer at rates of 2.5, 5.0 or 7.5 g/15 cm (6 in) pot. Plants produced in a Canadian sphagnum peat:pine bark mix were shorter and received lower plant grades compared to Fafard #4 and Vergro Container Mix. Height increase and plant grade for all plants was greater when fertilizer rate was increased from 0.21 to 0.42 g/L (0.79 to 1.58 g/gal), but height increase and plant grade did not improve much as fertilizer rates rose beyond 0.42 g/L (1.58 g/gal). In expt. 3, increase in height and plant grade for plants treated with 0.63 g/L (2.36 g/gal) soluble fertilizer was similar to height increase and plant grade for plants receiving the 5.0 and 7.5 g/15 cm pot slow release fertilizer.

Meeting and maintaining the proper watering requirements for indoor plants is a major obstacle to increased plant use in the home or office. Introduction of “self-watering” containers to the marketplace has been only marginally successful because of limited acceptability by consumers. Water use levels were determined for Codiaeum variegatum (L.) Blume ‘Petra’, Dieffenbachia maculata (Lodd) G. Don ‘Camille’, Dracaena fragrans (L.) Ker-Gawl. ‘Massangeana’, Epipremnum aureum (Linden & André) Bunt. ‘Golden Pothos’, Spathiphyllum (Schott.) ‘Gretchen’, and Syngonium podophyllum (Schott.) ‘White Butterfly’ established in self-watering containers and maintained under 2 light intensities commonly found in the home or office [12 and 24 μmol · s−l · m−2 (75 and 150 ft-c)]. Plant growth was better at 24 μmol · s−1 · m−2) (150 ft-c) than at 12 μmol · s−l · m−2 (75 ft-c) for all plants tested except Dieffenbachia, Dracaena and Spathiphyllum. Water utilization varied widely among plant genera, from a low of 1.4 ml H2O · cm−2 (0.3 oz · in−2) to a high of 4.8 ml H2O · cm−2 (1.0 oz · in−2) of leaf area over a 6-month period. All plants utilized more water at 24 μmol · s−1 · m−2 (150 ft-c) than at 12 μmol · s−1 · m−2 (75 ft-c) but water use was also dependent on plant genus and size.