Effects of Nitrogen and Potassium Rates and Ratios on Growth of English Ivy
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C.A. Conover, Ph.D., R. Caldwell, L.N. Satterthwaite and K. Steinkamp*
University of Florida
Institute of Food and Agricultural Sciences Research Report
CFREC-Apopka Research Report RH-96-8
English ivy (Hedera helix) cultivars suitable for interior use are grown primarily in hanging baskets, but they are also used in dish gardens, on small trellises placed in pots, as ground covers in large indoor combination planters and wherever a trailing effect is desired. Numerous cultivars-differing in leaf shape, size, variegation and growth habit-are available commercially; while the American Ivy Society lists hundreds of different known cultivars.
Historically, English ivy has been one of the indoor foliage plants commonly grown in northern greenhouses because of its ability to grow in a cool greenhouse (50-60°F). In addition, even though some English ivy has been grown in Florida since the 1930s, high temperatures and diseases made it an erratic crop. With increased use of cooled greenhouses, improved disease control methods and availability of many new cultivars, English ivy has become an important foliage plant in Florida during the past ten years.
Florida growers have refined their production systems over the years and most English ivy cuttings are obtained from plants that are used initially as stock and then are grown out and sold as foliage crops after having been cut back one, two or even three times for the cuttings. Stock plants are usually grown as hanging baskets for about a year before being sold. Since the number of cuttings placed in a pot may range from ten in a 4-inch pot to twenty-five in a 6-inch hanging basket and as high as fifty in an 8-inch basket, a large ivy producer needs many cuttings on a continuing basis.
References on English ivy fertilization are limited and general in nature, leaving growers concerned about nutrition of English ivy, especially nutrition of stock plants that may be grown for extended periods. This research was conducted to determine effects of different ratios of nitrogen (N) and potassium (K) on growth and quality of four popular cultivars of English ivy currently being grown in Florida nurseries.
Excellent quality plants of 'Asterick', 'Gold Dust', 'Ingrid Liz' and 'Starling' English ivy cultivars were obtained from a local nursery (Hermann Engelmann Greenhouses Inc., Apopka, FL 32704) at the end of August 1994. For each cultivar tested, cuttings were obtained from these plants and propagated, twenty cuttings per 6-inch hanging basket. Cuttings had two leaf nodes each and were obtained from the mid-sections of vines. Fafard #4 growing medium (Fafard of Florida, Inc., Apopka, FL 32703) amended with 1 lb/yd3 Micromax (The Scotts Company, Allentown, PA 18106) was used. All four cultivars were maintained in the same greenhouse where thermostats were set to maintain air temperatures from 65 to 90°F and maximum light intensities ranged from 1200 to 1500 ft-c in winter and 2500 to 2800 ft-c in summer. Plants were watered overhead two or three times per week as needed to adequately meet water requirements. Plants were fertilized once weekly using liquid fertilizer made from combining concentrated stock solutions containing the individual elements.
A 4 (N) x 4 (K) factorial test, with 16 fertilizer treatments and five replications per treatment, was initiated for each of the four cultivars tested. Fertilizer treatments began on December 12, 1994. At every fertilization, each hanging basket received 100 ml dilute fertilizer solution containing its assigned nutrient treatment-1.39, 2.46, 3.85 or 4.92 g N, 0.82 g P and 1.39, 2.46, 3.85 or 4.92 g K.
The hanging baskets were maintained as stock plants for 12 to 14 months. During that time, all cultivars were trimmed back to the rims of pots three times. On the first cutback date, trimmed off vines were measured, weighed and then discarded. On the second and third harvest dates, vines were cut back to rims of pots, then trimmed off vines were measured and weighed, and utilized in rooting experiments. Cuttings were harvested from each cultivar when plants had produced enough vines to provide an adequate crop of cuttings. Since cultivars grew at different rates, cutback dates differed.
Electrical conductivity (EC) and pH of growing medium leachate was determined using the pour-through method approximately one week after each cutback date. Length and weight of all vines cut off during the course of the experiment were determined by adding totals obtained at each of the three cutback dates.
'Asterick' English ivy baskets were propagated December 5, 1994, then trimmed back March 9, July 25 and December 14, 1995. Leachate pH and EC were measured March 17, August 4 and December 22, 1995. 'Gold Dust' cuttings were stuck October 3, 1994, then trimmed back February 20, June 14 and October 24, 1995. Leachate pH and EC were determined February 24, June 23 and November 3, 1995. 'Ingrid Liz' baskets were propagated September 30, 1994, then trimmed back February 2, May 25 and October 4, 1995. Leachate pH and EC were recorded February 10, June 2 and October 17, 1995. 'Starling' baskets were propagated October 5, 1994, then trimmed back January 31, June 6 and October 11, 1995. Leachate pH and EC were determined on February 3, June 16 and October 17, 1995. Treatments were terminated on December 22, 1995, after the last EC and pH results were obtained.
Results and Discussion
Of all the data collected, only pH of leachate collected from growing medium of 'Ingrid Liz' on June 2, 1995 was affected by an interaction of N and K fertilizer rates. However, the interaction had no effect on plant growth (results not shown).
Growing medium pH has been a concern of English ivy producers because of the gradual decrease over time. The pH of the leachate of the media of the cultivars grown in this experiment decreased with increasing N rates at each measuring, with the highest N rate continuing to lower pH through the duration of the experiment (Tables 1 and 2). It is important to note, however, that although low pHs did not seem to have an effect on plant growth, they were the result of excessive N levels.
Electrical conductivity of growing medium leachate, except that of 'Ingrid Liz' measured in October 1995, increased for all cultivars as both N and K rates increased (Tables 3 and 4). EC levels were lower for all cultivars by the second cutback, which is consistent with plant utilization of N and K. Although levels were somewhat high at the time of the earlier cutbacks, they were not excessive.
Number, length and weight of vines cut off increased at each cutback for each cultivar as was expected. However, number of vines per cultivar varied only slightly or not at all as N and K rates varied (Tables 5, 6, 7 and 8). Vine lengths varied significantly due to N and K treatments more often than number of vines did, but whether 170 to 180 cm/pot would increase the number of cuttings enough to be significant to a grower, especially since by the final cutback time (approximately one year after sticking "stock" pots) there were no differences due to treatments, is questionable. However, if size (weight) of cuttings is important to a grower, each cultivar varied in response to N, but generally lowest N yielded lowest weight and N at 2.46 or 3.85 g/6-inch pot/yr yielded highest weight.
'Gold Dust' did not produce an average of one vine per original cutting until the final cutback on October 24, 1995, a full year after sticking cuttings, indicating that it is a slow growing ivy. In contrast, 'Starling' nearly doubled in number of vines produced between the first and second cutbacks, indicating that it is a more prolific ivy.
When the data for vine length and weight of the three harvests are totaled for each of the four cultivars tested, it becomes obvious that response to N is much greater than response to K (Table 9). Increasing N had no effect on length of vines trimmed from 'Asterick' and 'Gold Dust', but did affect vine length of 'Ingrid Liz' and 'Starling'. Increasing N rate also increased weight of cut off plant material for all cultivars. Data indicates that the best N level is between 2.46 and 3.85 g/6-inch pot/yr.
Increasing K to 3.85 g/6-inch pot/yr increased total length and vine weight of 'Asterick' but did not affect other cultivars. Although not statistically significant, 3.5 g K/6-inch pot/yr did tend to produce the greatest vine weights and lengths for the other cultivars.
Summary
High quality English ivy hanging baskets were produced at a wide range of pH levels (3.7 to 6.9) indicating that growers' concerns that pHs below 5.0 adversely affect plant growth or quality were not supported in this research. Additionally, wide ranges in electrical conductivity were also noted but high ECs were not consistently related to shorter vine lengths and, thus, do not appear to inhibit growth of these ivy cultivars. Growth measurements did indicate that N and K levels of 2.46 to 3.85 g/6-inch pot/yr would generally produce the greatest number of cuttings per plant. Since nearly as many cuttings could be produced at 2.46 g N/6- inch pot/yr, this level of N is suggested to minimize the potential for nitrate-N leaching and possible environmental contamination, as well as the pH depression that concerns growers.
*professor Emeritus Environmental Horticulture, Biological Scientist, Statistician and Technical Assistant, respectively. Central Florida Research and Education Center, 2807 Binion Road, Apopka, FL 32703-8504.
References
- 1. Conover, C.A. and R.T. Poole. 1990. Light and fertilizer recommendations for production of acclimatized potted foliage plants. Nursery Digest 24(10):34-36, 58-59.
2. Chase, A.R. 1989. Nitrogen source and rate affect severity of Xanthomonas leaf spot of Hedera helix. CFREC-Apopka Research Report, RH-89-1. 6 pp.
3. Henley, R.W., A.R. Chase and L.S. Osborne. 1991. English ivy. CFREC-Apopka Foliage Plant Research Note RH-91-15. 11 pp.
4. Simone, G.W. and A.R. Chase. 1989. Disease control pesticides for foliage plant production. Revision 4. Extension Plant Pathology Report No. 30. 54 pp.
5. Sulgrove, Sabina Mueller. 1982. The care of ivies and the American Ivy Society ivy collection, second edition, The American Ivy Society, Dayton, OH. 16 pp.
Table 1. pHz of leachate of growing medium of hanging baskets of ivy cultivars fertilized using various N and K rates taken approximately 1 week after cutting vines back to the edge of the pot during 1995.
'Asterick' 'Gold Dust' N rate (g/6-inch pot/yr) Mar 17 Aug 4 Dec 22 Feb 24 Jun 23 Nov 3 1.39 6.5 6.5 6.6 6.5 6.9 6.5 2.46 6.0 6.1 6.3 6.0 6.7 6.3 3.85 5.5 5.9 5.2 5.3 5.4 4.6 4.92 5.0 5.0 4.1 4.8 4.1 3.7 SignificanceY Linear ** ** ** ** ** ** Quadratic ** ** ** ** ** ** K rate (g/6-inch pot/yr) 1.39 5.7 5.9 5.6 5.6 5.8 5.3 2.46 5.8 5.8 5.5 5.8 5.8 5.3 3.85 5.8 5.8 5.5 5.6 5.7 5.2 4.92 5.8 6.0 5.7 5.6 5.7 5.2 Significance Linear ns ns ns ns ns ns Quadratic ns ns ns ns ns ns zpH was transformed to hydrogen ion concentration before statistics were run, but results are discussed as pH.
Yns or **; Nonsignificant or significant at P =less than 0.01, respectively.
Table 2. pHz of leachate of growing medium of hanging baskets of ivy cultivars fertilized using various N and K rates taken approximately 1 week after cutting vines back to the edge of the pot during 1995.
'Ingrid Liz' 'Starling' N rate
(g/6-inch pot/yr)Feb 10 Jun 2 Oct 17 Feb 3 Jun 16 Oct 17 1.39 6.6 7.2 6.9 6.5 6.8 6.9 2.46 6.0 6.9 6.6 6.0 6.4 6.6 3.85 5.3 5.1 4.3 5.4 5.5 4.6 4.92 4.7 4.0 3.8 4.9 4.3 3.7 Significancey Linear ** ** ** ** ** ** Quadratic ** ** ** ** ** ** K rate(g/6-inch pot/yr) 1.39 5.8 6.0 5.6 5.7 5.9 5.5 2.46 5.6 5.7 5.4 5.8 5.8 5.5 3.85 5.7 5.7 5.4 5.6 5.6 5.4 4.92 5.7 5.7 5.3 5.7 5.8 5.4 Significance Linear ns ns ns ns ns ns Quadratic ns ns ns ns ns ns zpH was transformed to hydrogen ion concentration before statistics were run, but results are discussed as pH.
yns or **; Nonsignificant or significant at P =<0.01, respectively.
Table 3. Electrical conductivity (µmhos·cm-1) of leachate of growing medium of hanging baskets of ivy cultivars fertilized using various N and K rates taken approximately 1 week after cutting vines back to the edge of the pot during 1995.
'Asterick' 'Gold Dust' N rate
(g/6-inch
pot/yr)Mar 17 Aug 4 Dec 22 Feb 24 Jun 23 Nov 3 1.39 1772 813 504 1795 821 949 2.46 3505 1180 677 3212 1052 1469 3.85 3856 1650 915 4413 1052 1539 4.92 4610 1555 1045 4954 1731 2023 SignificanceZ Linear ** ** ** ** ** ** Quadratic ns ns ns ns ns ns K rate (g/6-inch pot/yr) 1.39 2631 843 523 2697 793 1062 2.46 3241 1284 713 3427 1002 1417 3.85 3565 1446 883 3939 1554 1633 4.92 4305 1624 1021 4311 1605 1868 Significance Linear ** ** ** ** ** ** Quadratic ns ns ns ns ns ns Zns or **; Nonsignificant or significant at P =<0.01 respectively.
Table 4. Electrical conductivity (µmhos-cm-1) of leachate of growing medium of hanging baskets of ivy cultivars, fertilized using various N and K rates, taken approximately 1 week after cutting vines back to the edge of the pot during 1995.
'Ingrid Liz' 'Starling' N rate
(g/6-inch
pot/yr)Feb 10 Jun 2 Oct 17 Feb 3 Jun 16 Oct 17 1.39 1601 691 722 1845 738 702 2.46 2792 762 1035 3070 858 1197 3.85 3635 1069 1308 4149 1297 1509 4.92 3788 1171 2179 5312 1283 1872 SignificanceZ Linear ** ** ** ** ** ** Quadratic * ns ns ns ns ns K rate (g/6-inch pot/yr) 1.39 2196 638 1395 2925 648 1004 2.46 2827 790 1016 3412 912 1093 3.85 3161 961 1275 3869 1240 1344 4.92 3633 1304 1559 4170 1376 1839 Significance Linear ** ** ns ** ** ** Quadratic ns ns ns ns ns ns Zns, * or **; Nonsignificant, significant at P =<0.05 or significant at P="<" 0.01, respectively.
Table 5. Number, length and weight of vines cut off ivy cultivar stock plants at three cut back times during an experiment in which plants were fertilized with various N and K rates.
Number of vines 'Asterick' 'Gold Dust' N rate
(g/6-inch
pot/yr)Mar 9 July 25 Dec 14 Feb 20 June 14 Oct 24 1.39 15.4 19.5 22.7 14.9 18.8 22.4 2.46 15.6 20.4 25.0 15.2 18.8 23.8 3.85 14.8 20.6 24.2 13.7 19.5 25.2 4.92 14.2 20.6 24.6 13.7 19.0 22.8 SignificanceZ Linear * ns ns * ns ns Quadratic ns ns ns ns ns * Length of all vines 1.39 176 708 984 141 508 874 2.46 201 825 991 179 561 852 3.85 191 866 983 169 519 837 4.92 184 860 945 186 528 817 Significance Linear ns ** ns * ns ns Quadratic * * ns ns ns ns Weight of all vines 1.39 24.9 74.8 128.2 20.7 57.4 98.4 2.46 29.4 109.8 163.6 26.3 76.0 121.8 3.85 26.6 114.6 156.2 25.0 78.2 114.7 4.92 26.0 119.6 150.0 27.5 75.3 108.4 Significance Linear ns * * * * ns Quadratic * * * ns * * Zns, * or **; Nonsignificant, significant at P =<0.05 or significant at P="<" 0.01, respectively.
Table 6. Number, length and weight of vines cut off ivy cultivar stock plants at three cut back times during an experiment in which plants were fertilized with various N and K rates.
Number of vines 'Ingrid Liz' 'Starling' N rate
(g/6-inch
pot/yr)Feb 2 May 25 Oct 4 Jan 31 Jun 6 Oct 11 1.39 14.5 21.2 25.7 16.8 27.7 37.4 2.46 15.2 22.7 27.1 16.7 29.4 39.6 3.85 14.2 24.1 29.0 15.4 29.4 39.2 4.92 14.2 23.4 26.8 14.9 29.2 38.6 SignificanceZ Linear ns ** ns ** ns ns Quadratic ns ns * ns ns ns Length of all vines 1.39 145 692 958 189 904 1239 2.46 183 783 909 194 991 1155 3.85 203 859 1044 183 1091 1229 4.92 207 850 917 176 1075 1217 Significance Linear ** ** ns ns ** ns Quadratic ns * ns ns ns ns Weight of all vines 1.39 16.2 56.7 89.8 20.2 69.0 101.8 2.46 19.2 72.3 97.2 21.7 88.8 117.8 3.85 20.4 77.0 100.4 20.2 99.2 115.4 4.92 20.0 71.2 87.5 19.8 97.2 109.1 Significance Linear ** ** ns ns ** ns Quadratic * ** ** ns ** ** Zns, * or **; Nonsignificant, significant at P =<0.05 or significant at P="<" 0.01, respectively.
Table 7. Number, length and weight of vines cut off ivy cultivar stock plants at three cut back times during an experiment in which plants were fertilized with various N and K rates.
Number of vines 'Asterick' 'Gold Dust' K rate
(g/6-inch
pot/yr)Mar 9 July 25 Dec 14 Feb 20 Jun 14 Oct 24 1.39 14.6 19.1 23.2 14.8 19.0 22.2 2.46 15.2 20.8 24.2 13.8 18.4 24.6 3.85 14.8 20.5 24.1 14.4 20.0 23.4 4.92 15.5 20.6 25.0 14.6 18.8 24.2 SignificanceZ Linear ns ns ns ns ns ns Quadratic ns ns ns ns ns ns Length of all vines 1.39 179 737 887 169 523 812 2.46 184 838 972 157 513 804 3.85 191 846 1056 177 539 889 4.92 199 839 987 171 540 876 Significance Linear ns * ** ns ns * Quadratic ns ns * ns ns ns Weight of all vines 1.39 26.0 95 138 25.3 69.0 107 2.46 26.2 106 148 24.2 73.4 104 3.85 26.7 108 160 26.1 71.4 120 4.92 28.0 111 153 23.9 73.2 112 Significance Linear ns * ** ns ns ns Quadratic ns ns ns ns ns ns Zns, * or **; Nonsignificant, significant at P =<0.05 or significant at P="<" 0.01, respectively.
Table 8. Number, length and weight of vines cut off ivy cultivar stock plants at three cut back times during an experiment in which plants were fertilized with various N and K rates.
Number of vines 'Ingrid Liz' 'Starling' K rate
(g/6-inch
pot/yr)Feb 2 May 25 Oct 4 Jan 31 Jun 6 Oct 11 1.39 14.8 22.7 26.4 15.8 28.4 36.3 2.46 15.0 23.4 28.0 15.8 30.2 38.5 3.85 14.4 22.2 26.6 16.0 29.3 41.0 4.92 13.8 23.2 27.6 16.1 27.8 39.0 SignificanceZ Linear ns ns ns ns ns * Quadratic ns ns ns ns * * Length of all vines 1.39 186 797 938 193 996 1144 2.46 178 798 956 183 1039 1169 3.85 194 820 952 191 1025 1274 4.92 179 770 981 175 1002 1252 Significance Linear ns ns ns ns ns ** Quadratic ns ns ns ns ns ns Weight of all vines 1.39 19.1 67.6 92.6 21.6 85.8 109 2.46 18.5 69.4 94.4 20.4 89.6 108 3.85 19.8 71.8 93.2 20.8 89.2 116 4.92 18.4 68.4 94.6 19.1 89.8 112 Significance Linear ns ns ns ns ns ns Quadratic ns ns ns ns ns ns Zns, * or **; Nonsignificant, significant at P S 0.05 or significant at P S 0.01, respectively.
Table 9. Total length (cm) and total weight (g) of vines trimmed off English ivy cultivars on three trimming datesZ.
'Asterick' 'Gold Dust' 'Ingrid Liz' 'Starling' N rate
(g/6-inch pot/yr)Lgth Wt Lgth Wt Lgth Wt Lgth Wt 1.39 1867 227 1523 178 1795 163 2332 191 2.46 2017 303 1592 224 1876 189 2340 228 3.85 2041 297 1524 218 2106 198 2503 235 4.92 1990 296 1531 211 1974 179 2468 226 SignificanceY linear ns ** ns ** ** ** * ** quadratic ns ** ns ** * ** ns ** K rate (g/6-inch pot/yr) 1.39 1803 258 1504 201 1922 179 2333 216 2.46 1994 280 1473 202 1933 182 2391 218 3.85 2093 294 1605 217 1966 185 2490 226 4.92 2025 292 1588 210 1931 181 2429 220 Significance linear ** ** ns ns ns ns ns ns quadratic * ns ns ns ns ns ns ns Z 'Asterick' baskets were trimmed back March 9, July 25 and December 14, 1995. 'Gold Dust' baskets were trimmed back February 20, June 14 and October 24, 1995. 'Ingrid Liz' baskets were trimmed back February 2, May 25 and October 4, 1995. 'Starling' baskets were trimmed back January 31, June 6 and October 11, 1995.
Yns, *, **; Nonsignificant, significant at P =<0.05 or significant at P="<" 0.01, respectively.