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Reichert, N.A. and B.S. Baldwin. 1996. Growth of bedding plants in a kenaf-based potting medium. p. 411-414. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Growth of Bedding Plants in a Kenaf-Based Potting Medium

Nancy A. Reichert and Brian S. Baldwin

  1. METHODOLOGY
  2. RESULTS
  3. REFERENCES
  4. Table 1
  5. Table 2
Kenaf (Hibiscus cannabinus L., Malvaceae) is an annual, tropical fiber crop that is currently being grown in the southern U.S. The outer bast (bark) fiber has been used in newsprint production and is being explored for use in textiles and other products (Goforth and Fuller 1994). However, few markets have been developed for the inner core fiber, which comprise 65%-70% of the stalk by weight. Studies have been conducted on the use of ground kenaf core as an amendment for greenhouse potting media in concentrations up to 100% (v/v). In that study, Wang (1994) determined that three foliage plants [Brassaia actinophylla Endl. (schefflera), Hibiscus rosa-sinensis L. (tropical hibiscus) and Pittosporum tobira (Thunb.) Ait.] grown in a 70 kenaf: 30 peat (v/v) medium were superior with regard to height, width and dry weight compared to those grown in two commercial media (Metro Mix 250 or Sunshine #1). Since kenaf core is a renewable biomass and is less expensive than sphagnum peat moss we initiated a study to determine if annual bedding plants could be successfully grown in a potting medium containing ground kenaf core as the primary component.

METHODOLOGY

Finely ground fresh kenaf core was obtained from Core Products, Charleston, Mississippi. A kenaf-peat potting medium composed of 70% (v/v) kenaf core and 30% (v/v) sphagnum peat moss contained the following amendments: 5.22 kg gypsum, 5.22 kg superphosphate, 4.75 kg dolomitic limestone, 0.95 kg Micromax Plus micronutrients (Scott Company), and 0.59 kg AquaGro 2000*G/m3 (Aquatrols of America). Slo-Cote slow release fertilizer (14% N-14% P2O5-14% K2O; Bonus Crop Fertilizer, Inc.) was added at 6.41 kg/m3 to the kenaf-peat medium and a commercial peat-based medium (Sunshine #1; Fisons Horticulture).

Twenty-three cultivars representing 17 ornamental and vegetable plant species (Table 1 and 2) were grown in kenaf-peat medium and commercial peat-based medium. Plants were started from seed and transplanted or purchased as plugs. All were transplanted into 72-cell bedding flat inserts. Each cell measured 3.7 cm2 x 5 cm deep, and one pack of 6 cells represented one replication (12 packs per sheet, 72 cells per tray). For each cultivar, there were six to 12 replications per medium. Supplemental nitrogen at 200 mg/l was provided to all plants twice weekly. Harvest dates were at 18 days (Capsicum, Limonium, Lycopersicon, Solanum, Tithonia), 4 weeks (Begonia, Celosia, Coleus, Impatiens, Ocimum, Petunia), 6 weeks (Salvia), 8 weeks (Tagetes), and 10 weeks (Ageratum, Catharanthus, Dianthus, Senecio) after transplanting.

RESULTS

There were no differences for total numbers of flowers or numbers of open flowers between the kenaf-peat medium and the peat-based medium with one exception--a single cultivar of Impatiens wallerana displayed greater numbers of open flowers in kenaf-peat medium (Table 1). Therefore, within all plant species tested, plants grown in kenaf-peat medium produced as many (or more, in one case) flowers as the peat-based medium. No differences were noted for plant heights in 15 of the plant species, but two (Celosia argentea and Lycopersicon esculentum) displayed greater heights in peat-based medium (Table 2). Shoot dry weights were similar for ten of the 17 plant species, but when different, they were greater for plants grown in peat-based medium (Tables 1 and 2). At harvest increased root masses for all plant species grown in kenaf-peat medium were observed. Wang (1994) also noted more vigorous root systems on the plants grown in kenaf-based media compared to commercial peat-based media. The emphasis on shoot and root growth for plants grown in kenaf-peat medium may account for the slightly lower shoot dry weights displayed by some plants species. Had dry weights been determined on whole plants instead of just shoot (above-ground) growth, differences in weights may not have existed. Various plant species grown in the two media were graded by the Mississippi State University Horticulture Judging Team. All received similar grades (very good to superior) regardless of the growing medium.

Annuals grown in the kenaf-peat medium, in general, performed as well as those grown in peat-based medium. Cost comparisons indicated that the kenaf-peat medium was much less expensive than the peat-based medium. New formulations of kenaf-based media are currently being developed to give similar or superior results when compared to other peat-based potting media. The lower cost of kenaf coupled with the decreasing availability of peat should make kenaf-based media an attractive alternative to conventional greenhouse potting media.

REFERENCES

Table 1. Growth of seven ornamental plant species in kenaf-peat and peat mix.

Cultivar Pottingz medium Plant ht. (cm) No. open flowers Total flowers Plant dry wt. (g)
Begonia xsemperflorens cultorum Hort. (wax begonia)
Ambassador Peat 10 9.0y --x 1.3
Scarlet Kenaf-peat 8 8.5 -- 1.2
Vodka Peat 10 5.8 -- 1.5
Kenaf-peat 10 8.8 -- 1.5
Catharanthus roseus (L.) (vinca)
Peppermint Peat 14 8.0 15.0 3.2
Cooler Kenaf-peat 12 6.8 14.8 2.9
Dianthus chinensis (L.) (pinks)
Princess Mix Peat 23 8.5 14.2 7.5
Kenaf-peat 22 8.8 13.6 6.4
Telstar Mix Peat 18 2.5 6.0 --
Kenaf-peat 15 4.5 6.5 --
Impatiens wallerana Hook. f. (impatiens)
Deco Orange Peat 21 6.8 14.3 2.5*
Kenaf-peat 14 9.2 13.2 1.3
Super Elfin White Peat 19 3.8 9.5 2.6
Kenaf-peat 17 3.5 12.7 2.1
Tempo Orange Peat 20 17.0 34.7 3.2
Kenaf-peat 18 21.8 42.0 2.9
Petunia xhybrida Hort. Vilm.-Andr. (petunia)
Celebrity Ice Mix Peat 24 5.2 6.4 4.8*
Kenaf-peat 19 3.5 4.8 2.6
Salvia splendens F. Sellow ex Roem. & Schult. (salvia)
Flare Peat 27 1.8 3.5 6.7*
Kenaf-peat 23 1.7 2.2 4.7
Tagetes erecta L. (marigold)
Inca Yellow Peat 15 1.6 5.5 4.1
Kenaf-peat 16 1.9 6.0 4.5
Bonanza Orange Peat 15 7.8 10.3 4.0
Kenaf-peat 15 8.1 12.3 3.3
Lemondrop Peat 11 3.3 5.2 2.3
Kenaf-peat 11 3.1 5.9 2.1
zPeat based mix = Sunshine #1; kenaf-peat = 70% kenaf core plus 30% peat.
yIn Begonia, numbers represent the number of flower stalks per 6-cell pack.
xMeasurement not taken.
*Paired numbers within a column differ by greater than one standard deviation.

Table 2. Growth of ten ornamental and vegetable plant species in kenaf-peat and peat mix.

Cultivar Pottingz medium Height (cm) Dry wt. (g)
Ageratum houstonianum Mill. (ageratum)
Danube Peat 16 4.2
Kenaf-peat 13 3.2
Capsicum annuum L. (bell pepper)
Blockbuster Hybrid Peat 13 1.5*
Kenaf-peat 11 1.0
Celosia argentea L. (cockscomb)
Treasure Chest Peat 5* 2.9
Kenaf-peat 4 1.4
Coleus blumei Benth. (coleus)
Wizard Golden Peat 15 3.6*
Kenaf-peat 14 2.1
Limonium sinuatum (L.) Mill. (statice)
Petite Bouquet Peat 20y 2.3
Kenaf-peat 19 1.9
Lycopersicon esculentum Mill. (tomato)
Heatwave Hybrid Peat 23* 2.4
Kenaf-peat 19 2.1
Ocimum basilicum L. (sweet basil)
Purple Ruffles Peat 13 --
Kenaf-peat 14 --
Senecio cineraria DC. (dusty miller)
Silver Dust Peat 9 3.9*
Kenaf-peat 7 1.8
Solanum melongena L. (eggplant)
Burpee Hybrid Peat 9 1.0
Kenaf-peat 8 1.0
Tithonia rotundifolia (Mill.) S.F. Blake
(Mexican sunflower)
Goldfinger Peat 10 -
Kenaf-peat 9 -
zPeat based mix = Sunshine #1; kenaf-peat = 70% kenaf core plus 30% peat.
yMeasurements represent the average of two plant widths.
*Paired numbers within a column differ by greater than one standard deviation.
All but one were initiated as seedling transplants (Coleus was initiated from plugs).

Last update June 17, 1997 aw