Regulating Perennial Plant Growth With Controlled Phosphorous Levels

Transcription

1 Regulating Perennial Plant Grwth With Cntrlled Phsphrus Levels ftrvi"d 1M Mrtililu!t illlimflry IUtU 1996 James T. Midcap Department f Hrticulture - Athens The University f Gergia Nature f Wrk: Many perennials make rapid grwth in spring and quickly becme vergrwn in their pts. There is little time t get the plants frm the prductin nursery t the retail utlet. The shelf life f these plants in the retail stre is relatively shrt. Many f these vigrus perennials d n respnd well t plant grwth regulatrs. There has been little that can be dne t regulate the plant grwth f these perennials. Als, there is a great cncern abut reducing the amunt f phsphrus leaching frm cntainers and cntaminating the surface and grund waters. The prductin f quality crps with reduced phsphrus levels wuld help grwers better manage their nutrient run ff. There have been crp reprts where lw phsphrus has an effect n the grwth f perennials. Lw levels f phsphrus have reduced the amunt f grwth withut causing deficiency symptms r greatly reducing quality. There was interest by Harrell's representatives t begin initial evaluatin f lw phsphrus fertilizers n vigrus grwing perennials. They prvided the funding and prducts fr this prject. Grwers at McCrkle Nurseries identified the fllwing as likely perennials t evaluate. Plants included in the trial were Armeria pseudarmeria 'Jystick Red', Crepsis auriculata 'Zamphir', Gaillardia grandiflra 'Burgundy', Leucanthemum 'Becky' and Rudbeckia specisa 'Viettes Little Suzy'. Perennial plugs were ptted n Nvember 6, 2003 int trade gallns filled with 6: 1 barksand mix amended with 4#/yd 3 dlmitic lime, 1.5 #/yd 3 gypsum and 2 #/yd 3 talstar. The fertilizer treatments included 1) Blended (0# P 2 0/yd 3 ), 2) Blended (0# P 2 0/yd 3 ), 3) Blended (0.29# P 2 0/yd 3 ), 4) Blended (0.43# P 2 0/yd 3 ), and 5) Osmcte (0.55# P z O/yd 3 ). All treatments supplied 1.65 # actual nitrgen / cubic yard f substrate. Minr elements were supplied with each treatment. Plants were wintered ver in sun n a gravel pad. Plants were cvered with a frst blanket when winter temperatures were expected t cause damage. Sil samples were cllected n March 18, 2004 fr all treatments and perennials. Samples were taken frm three separate pts and cmbined int a single sample. Grwth, height and spread were recrded during spring. Prductin f flwer buds and pen blms were recrded when applicable. Seventeen replicates f each treatment were used. Results and Discussin: The height and spread f the perennials were mnitred frm mid March thrugh mid May Treatment 1 and 2 prduced the least grwth while Treatment 5 prduced the greatest grwth. The grwth n Treatment 5 was excessive fr Armeria, Gaillardia and Leucanthemum. The Crepsis cultivar was a dwarffrm and the Rudbeckia prduced little grwth until the end f the mnitring perid. The tw intermediate phsphrus levels lked very gd as a methd f reducing grwth f sme vigrus perennials.

2 Figures 1-6 graphically illustrate the research results and phts f each treatment are included. The Armeria height was due t the length f the flwering stems. Treatments 2, 3 and 4 shw great prmise in reducing plant grwth ver treatment 5 (the nrmal rate). Treatment 2 with 0% P 205 was slightly better than treatment 1, with 0% P 205' This may be the result f the increased ptassium levels r the frmulatins used. It als appears that the crps culd be all planted at ne time in substrates with different phsphrus levels and stagger the dates f maturity. Pht 1. Armeria right - Treat 5, 2, 1, 3 and 4 n April 1, The Crepsis 'Zamphir' develped int a dwarf spreading frm. Treatments 1 and 2 were unacceptable. Treatments 3,4 and 5 prduced acceptable plants, with treatment 3 and 4 prducing shrter plants with delayed flwering. Pht 2. Crepsis right - Treat 5, 2, 1, 3 and 4 n April 1, Gaillardia 'Burgundy' prduced a linear increase in grwth and flwering as the phsphrus rates increased. The zer rates prduced little early grwth, hwever the higher rates wrked well. Gaillardia lks like a gd crp fr prductin under staggered phsphrus rates. Testing mre f the intermediate rates are needed. Leucanthemum 'Becky' did nt flwer but vergrew the pts in treatment 5. Treatments 1 and 2 were very week and slw t develp. Treatment 3 and 4 were acceptable at the terminatin f the trial.

3 Pht 3. Gaillardia right - Treat 5, 2, 1, 3 and 4 n April 1, Pht 4. Leucanthemum right - Treat 5, 2, 1, 3 and 4 n April 1, Rudbeckia 'Little Suzy' was very slw fr all treatments. This crp matures late in the seasn. By May 13, the pts had filled in but there was n flwer bud develpment. Treatments 3,4 and 5 had filled the pts at terminatin. Pht 5. Rudbeckia right - Treat 5, 2, 1, 3 and 4 n April 1, Significance t the Industry: The use f reduced phsphrus levels may be used t regulate grwth f excessively vigrus perennials withut detrimental effects. Reduced levels culd help reduce phsphrus run ff frm prductin nurseries. Staggered phsphrus levels in the ptting substrate culd stagger the maturity dates f perennial crps. The entire crp culd be planted all at ne time rather than staggering the planting dates. Further investigatin f a range f intermediate rates are necessary t determine their effectiveness under prductin cnditins.

4 Figure 1. Armeria 'Jystick Red' - Height & Spread (inches) r~ ~ 10~ ~~ ~ 8~ c ~ ==1 4 -t---===i 24--= Height 3/18 Height 4/1 Spread 3/18 Phsphrus Treatments Spread 4/1 ~ T ~ reat 1 [II Treat 2 ~ Treat 3 0 Treat 4 0 Treat 5 Figure 2. Armeria 'Jystick Red' - Number Buds & Flwers ,--r ~ ~ r 1 VI ~ 8 ~ u ~ t------' """ # FI Buds 4/1 # FI Buds 4/15 Phsphrus Treatments # Open Fls 4/15 ~ Treat 1 IliI Treat 2 I!il Treat 3 0 Treat 4 0 Treat 5

5 Figure 3. Crepsis 'Zamphir' - Height, Spread, Buds & Flwers. 16 ~ ~ 12~ ~ ~~~~1_ ~ (/) ~ 8~ <> ~ ~= 4-r-1~==l 2 r.~;;;;;d~ ~~ ~' ~ ~~~~~~ Height 4/1 Spread 4/1 # FI Buds 4/1 Phsphrus Treatments I1Jilll Treat 1 Treat 2 Ii Treat 3 D Treat 4 D Treat 5 # Open Fls 4/15 I/) Figure 4. Gaillardia 'Burgundy' - Height, Spread, & Flwer Buds. 16,, ~ r_r_ ~ 12~ ~ 10~ ~ ~ 8 ~ u c: 6 ~ _l 4 -t j 2 -t---le:g Height 4/1 Height 4/15 Spread 4/1 Spread 4/15 # FI Buds 4/15 # FI Buds 4/22 Phsphrus Treatments WI Treat 2 Treat 3 D Treat 4 D Treat5

6 Figure 5. Leucanthemum 'Becky' - Height & Spread (inches). 20~ ~ VI ~ ~ f:!!'ll:"! Height 4/1 Height 4122 Spread 4/1 Spread 4122 Phsphrus Treatments I); Treat 1, I Treat 2 R Treat 3 D Treat 4 D Treat 5 Figure 6. Rudbeckia 'Little Suzy' - Height & Spread (inches) ~ ~ 12~ ~~ VI 10~ (I) ~ 8~----~~_r~ ~=_~~ : Height 5/13 ~ Treat 1 Spread 4/1 Spread 4/15 Spread 5/13 Phsphrus Treatments Treat 2 ~ Treat3 0 Treat4 Treat5

7 Table 1. Phsphrus Levels (ppm) in Ptting Substrate fr Each Crp and Treatment n Treatments Armeria Crepsis Leucanthemum Gaillardia Rudbeckia #1 (0% P20S) #2 (0% P2OS) #3 (0.29% P2OS) NA* l.83 #4 (0.43% P2O S ) l.18 NA* 2.43 #5 (0.55% P 2 O S ) NA* 9.84 * Nt Available