Bedding plants and many vegetable crop seeds are often sown in plug trays. Some crops, like marigold (Tagetes sp. L.), tend to stretch early after germination, especially if grown in low light environments. By the time growers apply plant growth regulators (PGRs), stretching of the hypocotyl has already occurred and seedling applications are ineffective. Seedling height may be controlled by applying the plant growth regulator directly to the seed. Seeds of `Bonanza Gold' marigold (Tagetes patula L.), `Cherry Orbit' geranium (Pelargonium {XtimesX}hortorum L.H. Bailey), and `Sun 6108' tomato (Lycopersicon esculentum Mill.) were soaked for 6, 16, or 24 hours in paclobutrazol solutions of 0, 500, or 1000 mg·L-1. After the soak treatment, seeds were dried for 24 hours prior to laboratory germination testing or sowing in plug trays. Percentage of emergence and seedling height were measured 16, 26, and 36 days after sowing. Laboratory germination of treated seeds was less than that of the control, which was attributed to the PGR being concentrated around the seed on the blotters. In contrast, seedling survival was unaffected in plugs. The higher concentration of PGR and longer times of soaking increased growth regulation, but also inhibited emergence of geraniums (71% vs. 99%). When seeds were imbibed 6, 16, or 24 hours, growth restriction was 31%, 31%, and 40%, respectively, for tomato, 61%, 37%, and 76%, respectively, for geranium and 30%, 38%, and 41%, respectively, for marigold. These results indicate that PGR application to geranium, marigold, and tomato seeds may be feasible using a 6- or 16-hour soak in 500 mg·L-1 paclobutrazol. Chemical name used: (±)-(R*,R*)-ß-[(4-chlorophenyl)methyl]-{XsalphaX}-(1,1-dimethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

The objective was to evaluate and compare foliar spray and soil drench application methods of iron (Fe) for correcting Fe deficiency in hybrid calibrachoa (Calibrachoa × hybrida) grown in a container medium at pH 6.9 to 7.4. Untreated plants showed severe chlorosis and necrosis, stunting, and lack of flowering. An organosilicone surfactant applied at 1.25 mL·L-1 (0.160 fl oz/gal) increased uptake of Fe from foliar applications of both ferrous sulfate (FeSO4) and ferric ethylenediamine tetraacetic acid (Fe-EDTA). Foliar sprays at 60 mg·L-1 (ppm) Fe were more effective when Fe was applied as Fe-EDTA than FeSO4. Increasing Fe concentration of foliar sprays up to 240 mg·L-1 Fe from Fe-EDTA or 368 mg·L-1 Fe (the highest concentrations tested) from ferric diethylenetriamine pentaacetic acid (Fe-DTPA) increased chlorophyll content compared with lower spray concentrations, but leaf necrosis at the highest concentrations may have been caused by phytotoxicity. Drenches with ferric ethylenediaminedi(o-hydroxyphenylacetic) acid (Fe-EDDHA) at 20 to 80 mg·L-1 Fe were highly effective at correcting Fe-deficiency symptoms, and had superior effects on plant growth compared with drenches of Fe-DTPA at 80 mg·L-1 Fe or foliar sprays. Efficacy of Fe-DTPA drenches increased as concentration increased from 20 to 80 mg·L-1 Fe. An Fe-EDDHA drench at 20 to 80 mg·L-1 Fe was a cost-effective option for correcting severe Fe deficiency at high medium pH.

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A mathematical description for the relationship between the rate of rose (Rosa hybrida L.) leaf net photosynthesis and photosynthetically active radiation, leaf temperature, and leaf age is developed. The model provides a tool for the prediction of these rates for leaves growing in a rose crop canopy.

Shoot stretching in plug production reduces quality and makes mechanized transplanting difficult. The objectives of this study were to measure seedling emergence and shoot height of plugs as affected by paclobutrazol application during seed soaking, priming, or coating on seedling emergence and height. Verbena (Verbena ×hybrida Voss. `Quartz White'), pansy (Viola wittrockiana L. `Bingo Yellow Blotch'), and celosia (Celosia cristata L. `New Look') seeds were soaked in water solutions of paclobutrazol and subsequently dried on filter paper at 20 °C for 24 h. Soaking seeds in paclobutrazol solutions before sowing reduced growth and percentage seedling emergence of verbena and pansy but had little effect on those of celosia. Verbena seeds soaked in 50, 200, or 500 mg paclobutrazol/L for 5, 45, or 180 min produced fewer and shorter seedlings than controls. Osmopriming verbena seeds with 10 to 500 mg paclobutrazol/L reduced seedling emergence. Seedling height and emergence percentage of pansy decreased with increasing paclobutrazol concentrations from 2 to 30 mg·L–1 and with soaking time from 1 to 5 min. The elongation of celosia seedlings was reduced by soaking seeds in 10, 50, 200, or 500 mg paclobutrazol/L solutions for 5, 180, or 360 min. However, these reductions were negligible and without any practical application.

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`Candy Sunblaze' and `Red Sunblaze' miniature roses (Rosa L. sp.), were grown at several temperatures. The phenological events of budbreak (BB), visible flower bud (VB), and open flower (OF) were recorded daily. Based on these events, phenophases from BB to VB (BB:VB), from VB to OF (VB:OF), and from BB to OF (VB:OF) were defined. Daily rates of development to complete a phenophase increased with temperature between 13.6 and 27 °C. For `Candy Sunblaze', the rate of increase changed to a smaller slope beyond 25 °C. A piecewise linear regression change point model was fitted to each dataset. The base temperature (Tb) and the temperature at which the nonlinearity (Ti) occurred could then be determined. Tb for the phenophase BB:OF was 9.5 °C for `Candy Sunblaze' and 8.1 °C for `Red Sunblaze'. Ti for `Candy Sunblaze' was 24.9 °C for BB:VB and 25.6 °C for the phenophase BB:OF. The resulting point of change in rate of development prompted a modification of the traditional thermal unit formula. To complete the phenophase BB:OF using the modified formula, 479 degree days (°Cd) were predicted necessary for `Candy Sunblaze' and 589 °Cd for `Red Sunblaze'. Predicted time of events was compared with observed values. Subdividing BB:OF into BB:VB and VB:OF and using their respective Tb and thermal units summations (TU) reduced the average prediction error from 1.9 to 1.8 days for `Candy Sunblaze' and from 2.4 to 1.5 days for `Red Sunblaze'. In addition to single plant observations, phenological observations and thermal units were determined for pots with four plants to simulate commercial greenhouse crop production. Subdividing BB:OF into BB:VB and VB:OF and using their respective Tb and TU accumulations, reduced OF prediction errors on a crop basis for `Red Sunblaze', but was ineffective for `Candy Sunblaze'.