|Jmol-3D images||Image 1|
|Molar mass||293.79 g mol−1|
|Appearance||off-white to beige solid|
|Boiling point||460.9 °C at 760 mHg|
|Solubility in water||26 mg/L (20°C)|
|Flash point||232.6 °C; 450.7 °F; 505.8 K|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
Paclobutrazol (PBZ) is a plant growth retardant and triazole fungicide. It is a known antagonist of the plant hormone gibberellin. It acts by inhibiting gibberellin biosynthesis, reducing internodial growth to give stouter stems, increasing root growth, causing early fruitset and increasing seedset in plants such as tomato and pepper. PBZ has also been shown to reduce frost sensitivity in plants.
PBZ is used by arborists to reduce shoot growth and has been shown to have additional positive effects on trees and shrubs. Among those are improved resistance to drought stress, darker green leaves, higher resistance against fungi and bacteria, and enhanced development of roots. Cambial growth, as well as shoot growth, has been shown to be reduced in some tree species.
PBZ is normally applied to the soil to be taken up by the roots and transported via the xylem to the upper parts of the plant. Foliar application is mostly ineffective. Seeds can be soaked with PBZ to reduce seedling growth.
For Trees and Shrubs
Paclobutrazol is used by arborists to reduce shoot growth and has been shown to have additional positive effects on trees and shrubs. It is used to improve their resistance to drought stress, darker green leaves, higher resistance against fungi and bacteria, and enhanced development of roots. Cambial growth, as well as shoot growth, has been shown to be reduced in some tree species.
For Aggressive Crops
Early paclobutrazol applications are desirable once roots have reached the pot edges, typically seven to 10 days after transplant. Growers are encouraged to perform their own trials to determine appropriate rates for their growing conditions and specific crops. The effects are strongly recommended.
Paclobutrazol, particularly when delivered as a spray, can delay flower development and reduce flower size. This application should generally be used as a last resort. 
- Berova, Malgorzata; Zlatev, Zlatko (2000). Plant Growth Regulation 30 (2): 117. doi:10.1023/A:1006300326975 http://www.springerlink.com/index/VG02K661X2N0PG32.pdf
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- Grossi et al. (2005). "Effects of paclobutrazol on growth and fruiting characteristics of Pitanga ornamental pepper". Acta Horticulturae 683: 333–336.
- Chaney et al. 1996[vague]
- Fletcher et al. 2000[vague]
- Rademacher 2000[vague]
- Chaney 2003[vague]
- Bai et al. 2004[vague]
- Pasian and Bennett, Paclobutrazol-Soaked Ornamental Kale Seeds Produce Short Seedlings
- CAS Database Reference, Main Application of Paclobutrazol: trees&shrubs;aggressive crops; flowers