BA Application Promotes Offset Formation in Hosta Cultivars

James M. Garner, Gary J. Keever, D. Joseph Eakes, and J. Raymond Kessler

Previous studies demonstrated the effectiveness of benzyladenine (BA), marketed as BAP-10, in promoting the outgrowth of buds in hosta. Furthermore, offsets formed from BA-induced buds could be removed from the mother plant soon after elongation and rooted under intermittent mist. Initial studies were conducted using blue hosta yet considerable differences in response to BA application may be expected among the more than 1,500 hosta cultivars available. A study was conducted in 1995 to determine differences among hosta cultivars in response to BA. Of 10 cultivars evaluated, BA application promoted offset formation in five cultivars. To more fully understand the response of hosta cultivars to BA, this study evaluated 10 additional hosta cultivars in 1996.

Methods

Single-eye (no offsets) plants of 10 hosta cultivars (Table 1) were treated with a foliar application of 0, 1,250, 2,500, or 3,750 parts per million (ppm) of BA at 0.5 gallon/ 100 feet2 on June 4, 1966. At 30 and 60 days after treatment (DAT), visible offset counts and a growth index were determined for each plant.

Results

BA application promoted offset formation in all cultivars evaluated, but the response to BA concentration was cultivar-dependent. At 30 DAT offset counts in treated plants were higher than those of controls in 8 of the 10 cultivars (Table 1). Optimal BA concentration varied among cultivars. Offsets formed in controls of all cultivars except Halcyon (HC) and Samuel Blue (SB) at 30 DAT. Plants of HC receiving 3,750 ppm BA averaged 3.1 offsets, and plants of SB receiving 1,250 ppm BA averaged 5.9 offsets. In treated plants of the remaining cultivars, increases in offsets at the numeric optimum of the tested rates ranged from 0.9 offset for Stiletto (ST) to 6.2 offsets for Hyacinthina (HY), compared to controls. Optimal increase in offsets in ST, HC, HY, and Patriot (PT) was at 3,750 ppm BA, while in Great Expectations (GE), Golden Tiara (GT), SB, Fragrant Blue (FB), Medio variegata (MU), and Shade Fanfare (SF) maximum offset numbers were produced at 1,250 ppm.

At 60 DAT, offset counts for treated plants were higher than those of controls in all cultivars. In HC, no offsets formed in controls by 60 DAT, but plants receiving 3,750 ppm BA averaged 3.8 offsets. In the remaining cultivars, at the numeric optimum of the three BA rates, increases in offsets among treated plants at 60 DAT ranged from 2.1 offsets in GE to 7.6 offsets in ST, compared to controls.

Compared to controls, growth index of treated plants was increased or unaffected by BA treatment (data not shown). At 30 DAT, the growth index was higher for treated plants than for controls of HY and PT, with the growth index increasing with increasing BA rate. Growth index for treated plants was similar to controls in other cultivars at 30 DAT. At 60 DAT, the growth index was higher for treated plants than for controls in PT, SB, and ST, and similar to controls for all other cultivars. No phytotoxic symptoms were noted in any treatments in this study, and in many cases, plant appearance was enhanced by BA application due to outgrowth of BA-induced offsets.

Results of this study indicated that foliar application of BA can promote offset formation in a wide range of cultivars, BA application resulted in higher offset counts for plants of all evaluated cultivars within 60 days of BA application. Rate response was cultivar-dependent, with numerical optimum of the tested BA rates at 1,250 ppm for half the cultivars evaluated and at 3,750 ppm for the remaining cultivars.

Application of BA to hosta may reduce costs and accelerate production for a wide range of cultivars, including cultivars which are slow to produce offsets. In a previous study, BA application promoted offset formation in 50% of the cultivars evaluated, while in this study, BA application promoted offset formation in all cultivars within 60 DAT. These findings suggest that BA is effective in promoting offset formation in a wider range of cultivars than previously demonstrated.

Offset Counts of Hosta Cultivars at 30 and 60 Days After Treatment (DAT)
with Four BA Rates.
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BA rateFB1GEGTHC HYPTSB SFSTUM
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30 DAT
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0 0.4 0.1 3.5 0.0 1.6 1.0 0.0 2.4 1.4 1.9
1250 3.1 2.2 6.8 0.2 6.9 3.8 5.9 8.3 1.0 3.9
2500 1.8 2.2 6.5 1.0 4.9 3.6 4.9 7.7 2.0 2.4
3750 3.1 1.9 5.6 3.1 7.8 5.5 5.5 7.1 2.3 3.0
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60 DAT
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0 1.7 0.6 4.3 0.0 2.9 2.3 0.1 4.3 3.5 2.2
1250 3.6 2.7 6.9 0.2 8.1 4.0 6.9 8.5 7.1 4.4
2500 4.2 2.4 6.5 1.5 5.0 3.8 5.4 7.7 9.4 2.8
3750 3.8 2.3 5.7 3.8 0.9 5.7 5.9 7.2 11.1 3.7
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1FB=Fragrant Blue, GE=Great Expectations, GT=Golden Tiara, HC=Halcyon, HY=Hyacinthina, PT=Patriot, SB=Samuel Blue, SF=Shade Fanfare, ST=Stiletto, UM=Medio variegata.

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