HORTSCIENCE 26(9):1168-1170. 1991. characteristics of Hippeastrum (Amaryl1is). A preliminary trial, conducted in 1988- Planting Medium Effects on Forced 89, demonstrated that there were consider- able differences in response to planting me- Swaziland- and Dutch-grown dia. Thus, a large trial was conducted during the 1989-90 forcing season. From each pro- duction source, 135 bulbs (28 to 30 cm in Hippeastrum Hybrids circumference) of each cultivar were ob- A.A. De Hertogh1 and M. Tilley2 tained. Bulbs (‘Summertime’ and ‘Sun of Dance’) from Swaziland were shipped on 24 Department Horticultural Science, North Carolina State University, July 1989, arrived at Raleigh, N.C., on 17 Raleigh, NC 27695- 7609 Aug., and were stored in cardboard shipping Additional index words. Amaryllis hybrids, root growth, flowering cartons at 9C until planted. Bulbs (‘Apple Blossom’ and ‘Red Lion’) from The Neth- Abstract. The Swaziland-grown Hippeastrum bulbs ‘Summertime’ and ‘Sun Dance’ erlands were air-freighted in cardboard boxes reached the market and flowering stages of development in fewer days than the Dutch- on 3 Nov. 1989, arrived on 7 Nov., and were grown bulbs ‘Apple Blossom’ and ‘Red Lion’. ‘Sun Dance’ was the quickest flower and stored at 13C. The difference in the preplant- ‘Red Lion’ the slowest. The effects of the planting medium on days to market and ing storage temperature used (Vijverberg, flowering were variable and no medium appeared to be the best for this criterion. 1980, 1981) was due to the presence of ‘Summertime’ and ‘Red Lion’ produced longer leaves at flowering than ‘Apple Blossom’ emerged leaves in the Swaziland-grown bulbs. and ‘Sun Dance’. Three media that led to the production of the longest leaves, a Planting dates were 10 Oct. and 16 Nov. desirable trait, were: Sunshine no. 4, Fafard 3-B, and Sunshine Post-Harvest. ‘Apple for the Swaziland- and Dutch-grown bulbs, Blossom’ was the tallest cultivar followed by ‘Sun Dance’, ‘Red Lion’, and ‘Summer- respectively. Bulbs were planted with one- time’. Effects of the planting medium on total plant height were variable. The overall third of the bulb above the surface of the plant quality ratings for use as potted plants ranged from 3.4 to 3.8 out of 4 for medium in 15-cm diameter, standard depth ‘Summertime’, ‘Sun Dance’, and ‘Red Lion’. ‘Apple Blossom’ was rated 3.0 because it (1.8 liter) plastic pots. Fifteen pots were used was tall and had short leaves. It would be suitable as a cut flower. Regardless of the per planting medium and cultivar. After a planting medium used, ‘Apple Blossom’ lost the greatest amount of old basal roots. thorough initial watering, all bulbs were Consequently, it produced many new basal roots. The planting medium had variable blocked by cultivar on the same heating mat. effects on old and new basal roots and secondary root growth, depending on the cul- The planting media (Table 1) were random- tivar. Based on all the flowering criteria and the rooting responses, the best media for ized per cultivar. This was necessary be- all cultivars as potted plants were Fafard 3-B and Sunshine Mix no. 4. Fafard no. 2 cause the growth varied for each cultivar and was best for cut-flower usage since it produced taller plants with a good root system. medium, and they had to be watered only as needed. All pots were placed on electrically Hippeastrum spp. are indigenous to Cen- of the bulbs may dry out. To produce quality controlled heating mats that maintained the tral and South America (Liberty Hyde Bailey plants, a new viable root system must be medium at 23 ± 1C. None of the plants Hortorium, 1976). In the floriculture indus- established as quickly as possible after plant- were fertilized and they were grown under try, however, they are generally known as ing. One of the major factors that affect root prevailing light conditions. Data were ana- Amaryllis (Vijverberg, 1980, 1981). Hip- development is the planting medium (Gen- lyzed as a randomized complete block with peastrum have been extensively bred and ders, 1973). Also, it is known with tulips each cultivar serving as a block. Means sep- grown in The Netherlands and South Africa. that aeration is an important factor for root aration was by Duncan’s new multiple range This has led to development of many culti- development (De Haan and Van der Valk, test. Data for cultivars from the same pro- vars (Zandbergen, 1980). For use in North 1971; Van der Valk, 1971; Wiersum, 1971). duction source were combined when the in- America (De Hertogh, 1989), bulbs grown Thus, the objective of this study was to eval- teraction with the planting medium treatments in the above countries must be washed free uate the effects of seven commercially avail- was nonsignificant. of soil immediately after harvest to comply able planting media and two formulated at Marketing stage was recorded when the with plant quarantine regulations. The bulbs our laboratory on the forcing and rooting first floral stalk had reached 30 cm above subsequently are stored for several weeks and then transported for 2 to 5 weeks. As a result Table 1. Description of planting media used. of these handling procedures, the basal roots Basic constituents Received for publication 6 Dec. 1990. We ac- Equal volumes shredded pine bark, sand, sphagnum peat, sandy knowledge the donation of the bulbs by Swazibulb loam soil plus dolomitic (5.23 kg-m-“) and hydrated lime (Pty) Limited, Nhlangano, Swaziland, and The (1.31 kg·m-3) mixed, then sterilized. Dutch Bulb Exporters Assn., Hillegom, The Neth- 2 Sandy loam : 1 sand : 1 sphagnum peat (by volume) plus erlands. The latter organization also provided fi- dolomitic (5.23 kg·m-3) and hydrated lime (1.31 kg.m-3) nancial support for this research. We acknowledge mixed, then sterilized. the donations of the various planting media by: Sphagnum peat, perlite, vermiculite, nutrient charge, starter ASB-Greenworld, Inc., Farfard, Inc., W.R. Grace fertilizer, superphosphate, trace elements, wetting agent, and and Co., and Fison Western Corp. Lastly, we want Bentonite clay. to thank W. Swallow and L. Lehman for their Sphagnum peat, perlite, vermiculite, nutrient charge, starter assistance with the statistical analyses and P. Breed fertilizer, superphosphate, trace elements, and wetting agent. and A. Rutte for technical assistance. The use of Bark, sphagnum peat, perlite, vermiculite, nutrient charge, starter trade names in this publication does not imply en- fertilizer, superphosphate, trace elements, and wetting agent. dorsement by the North Carolina Agricultural Re- Pine bark ash, sphagnum peat, sand, vermiculite, nutrient charge, search Service of the products named, nor criticism starter fertilizer, trace elements, and wetting agent. of similar ones not mentioned. The cost of pub- Pine bark ash, sphagnum peat, sand, vermiculite, nutrient charge, lishing this paper was defrayed in part by the pay- starter fertilizer, trace elements, and wetting agent. ment of page charges. Under postal regulations, Sphagnum peat, perlite, limestone, nutrient charge, trace ele- this paper therefore must be hereby marked ad- ments, and wetting agent. vertisement solely to indicate this fact. 1 Sphagnum peat, perlite, nutrient charge, trace elements, wet- Professor. ting agent, Bentonite clay, and superabsorbent polymers. 2Agricultural Research Technician.

1168 HORTSCIENCE, VOL. 26(9), SEPTEMBER 1991 the nose of the bulb (Fig. 1). Flowering data basal roots is an important aspect for Hip- sequent years by the consumer (De Hertogh, were recorded when the first flower of the peastrum forcing and the bulb growers and 1989). first floral stalk opened fully. On that date, exporters must protect these roots as much Swaziland-grown cultivars reached the total plant height of the first flower stalk was as possible. Also, while there are many in- market and flowering stages of development measured from the rim of the pot to the up- herent cultivar differences (Vijverberg, 1980, in fewer days than Dutch-grown cultivars permost petal of the open flower. Total leaf 1981), plant breeders should select for a per- (Table 3). ‘Sun Dance’ reached both stages length was measured from the rim of the pot. sistent root system. earlier than ‘Summertime’, which agrees with Overall plant quality ratings (4 = excellent, After the last flower of the first floral stalk earlier forcing trials (De Hertogh, 1989). 1 = poor) were recorded on that same date. opened, the root systems of the bulbs were ‘Apple Blossom’ reached both stages in fewer This rating is subjective and includes length carefully washed in tap water until free of days than ‘Red Lion’, which is in agreement of the leaves, strength of the floral stalk and the planting medium. The basal plate with with results of Vijverberg (1980, 1981). The leaves, the presence of Stagnospora, and the roots were cut on 8 and 14 Nov. for ‘Sun transition period from market stage to flow- overall flower size. Dance’ and ‘Summertime’, respectively, 25 ering was 6 days for ‘Sun Dance’, 9 days The root system for Hippeastrum consists Jan. for ‘Apple Blossom’, and 27 Feb. for for ‘Summertime’, and 16 days for ‘Apple of contractile basal roots that produce sec- ‘Red Lion’, and stored in plastic bags at 2C. Blossom’ and ‘Red Lion’. These data pro- ondary branch roots (Fig. 2). Initial basal As soon as all the root and basal plate col- vide an indication of the potential days avail- root weight was 36.8, 41.5, 16.5, and 16.7 lection of the entire cultivar was completed, able for market distribution. g for ‘Summertime’, ‘Sun Dance’, ‘Apple roots were subsequently cut from the basal Although the various planting media pro- Blossom’ and ‘Red Lion’, respectively. From plate. They were classified as old or new duced statistically significant differences in these weights, it was obvious that the Swa- basal roots and new secondary roots, and the days to reach market and flowering stages ziland bulbs had retained more live roots than weighed to the nearest 10 mg. for Swaziland cultivars, the range was quite the Dutch-grown bulbs (Table 2). This dif- When evaluating these data (Tables 2 and small and commercially not important (Table ference may be due either to the cultivars or 3), it is important to keep in mind that the 3). Because Dutch-grown bulbs took longer the environment; the Swaziland bulbs were major use for Hippeastrum in North America to force, there were significant treatment dif- grown outdoors while the Dutch bulbs were is as a potted plant that will be first forced ferences and the two Dutch cultivars did not grown in greenhouses. Preserving the old and then maintained for flowering in sub- respond similarly to the different media.

HORTSCIENCE, VOL. 26(9), SEPTEMBER 1991 1169 produced significantly longer leaves in F2 Fafard mixes were best. F2 induced the larg- than in other media (Table 3). ‘Summer- est total root mass for ‘Summertime’ and ‘Sun time’, however, had significantly longer Dance’, but it was not significantly different leaves than ‘Sun Dance’. In contrast to pre- from six other mixes. The NCSU mixes re- vious reports (Vijverberg, 1980, 1981) that sulted in significantly less total root weight the leaves of ‘Apple Blossom’ and ‘Red Lion’ for all cultivars. For ‘Apple Blossom’, the should have been of equal length, our results largest total root mass was obtained with SM4 (Table 3) indicated differences for the two and SPH. F2 and M350 resulted in the low- cultivars. This difference could be a produc- est root mass. ‘Red Lion’ produced the tion year or a postharvest storage treatment greatest root mass with F3B, but the results effect. We have observed this difference in were similar for six other mixes. other trials. The planting media significantly SM4 not only preserved the old basal roots affected the leaf length of both cultivars (Ta- but also promoted growth of new basal roots ble 3). SM4, F3B, and SPH led to the pro- and secondary roots. It was followed by F2, duction of the longest leaves for both Dutch SPH, then F3B. The media that induced the cultivars. The tallest plants were ‘Apple poorest roots were NCB, NCSH, and ASB. Blossom’ followed by ‘Sun Dance’, ‘Red By evaluating all the flowering criteria Lion’, and then ‘Summertime’, with the lat- (Table 3) for potted Hippeastrum as well as ter two being in the desired total plant height the rooting responses (Table 2), FB3 and SM4 range (<50 cm) for potted plants. Although resulted in the best plants. They were fol- Fig. 1. Example of potted Hippeastrum plant at there were statistically significant differ- lowed by SPH. F2 produced the tallest plants, optimal market stage of floral and leaf devel- ences in heights, the effects of the various which is desirable for cut-flower forcing. opment. planting media were variable, especially from Although a component like sphagnum peat a commercial viewpoint. For example, the is common to F2, F3B, and SM4, it is not shortest plants of ‘Summertime’ grew in SM4, possible to conclude what components con- but so did the tallest plants of ‘Apple Blos- stitute the optimal planting medium for Hip- som’ and ‘Red Lion’. With ‘Sun Dance’ there peastrum. We believe that particle size is a was no difference. factor and that this is related to both moisture The effects of the planting medium on retention and drainage. It is obvious that fur- overall plant quality were minimal (Table 3). ther research is needed to elucidate the spe- ‘Summertime’, ‘Sun Dance’, and ‘Red Lion’ cific components and their ratios for best were highly acceptable as potted plants. growth of Hippeastrum. ‘Apple Blossom’ was only rated “good” as a potted plant because it was tall with short Literature Cited leaves. It appears more desirable for cut- De Haan, F.A.M. and G.G.M. Van der Valk. flower usage. 1971. Effect of compaction of physical prop- Characteristics such as number of floral erties of soil and root growth of ornamental bulbs. stalks per bulb and number of flowers per Acta Hort. 23:326-332. stalk were recorded, but data were not re- De Hertogh, A.A. 1989. Holland bulb forcers ported because these factors are predisposed guide. 4th ed. Intl. Flower Bulb Ctr., Hillegom, by bulb size and cultivar. They were not sig- The Netherlands. nificantly affected by the media used. Genders, R. 1973. Bulbs, A complete handbook ‘Apple Blossom’ was the only cultivar that of bulbs, corms and tubers. Robert Hale & Co., lost a significant amount of old basal roots London. regardless of the planting medium (Table 2). Liberty Hyde Bailey Hortorium. 1976. Hortus third: F3B, SM4, and SPH produced the lowest a concise dictionary of plants cultivated in the Fig. 2. Example of well-rooted ‘Sun Dance’ loss of the old basal roots. As a result, ‘Ap- United States and Canada. 3rd ed. Macmillan, Hippeastrum in Sunshine Mix no. 4. The con- ple Blossom’ produced significantly more new New York. tractile and secondary roots are identified. basal roots than ‘Red Lion’. ‘Red Lion’, Van der Valk, G.G.M. 1971. Influence of short however, had a larger basal root system than periods of restricted soil aeration on develop ‘Apple Blossom’ planted in F3B were the ‘Apple Blossom’ and this result agrees with ment of tulips. Acta Hort. 23:333-337. quickest to flower, while those planted in the Vijverberg’s (1980, 1981) findings. With Vijverberg, A.J. 1980. De teelt van Hippeastrum ‘Summertime’, F2 induced the most new basal (Amaryllis). Bloembollenteeltinformatie no. 17. NCR were the slowest. In contrast, ‘Red Lion’ Proefstation voor Tuinbouw onder Glas te planted in the NCS were the quickest, while roots, while NCB the fewest. For ‘Sun Naaldwijk, Proefstation voor de Bloemisterij te those in NCB, ASB, M360, and SPH were Dance’, SPH induced the most new basal Aalsmeer, Consulentschappen voor de Tuin- the slowest. Thus, there was no obvious best roots and NCS the fewest. For ‘Apple Blos- bouw te Aalsmeer en Naaldwijk, The Nether- mix for all the cultivars as far as days to som’ and ‘Red Lion’, new basal root growth lands. flower was concerned. was enhanced by SM4 and M350 and M360, Vijverberg, A.J. 1981. Growing Amaryllis. Grower Two very important factors in determining respectively. F2 induced the largest amount Guide no. 23, Grower Books, London. plant quality of potted Hippeastrum are the of secondary root growth with ‘Summer- Wiersum, L.K. 1971. Tulip root behaviour and presence and total length of the leaves and time’ and ‘Sun Dance’, while NCB, NCS, aeration requirements. Acta Hort. 23:318-325. total plant height. Ideally, a forced plant and ASB induced the least amount of root Zandbergen, F. 1980. Alfabetische lijst van de in should have leaves >50% of the total plant growth. For ‘Apple Blossom’, the two Sun- Nederland in cultuur zijnde Amaryllis (Hip- height, which should be » 40 to 50 cm at shine mixes led to the most secondary root peastrum) cultivars. Kon. Alg. Ver. Bloembol- flowering. ‘Summertime’ and ‘Sun Dance’ growth, while, for ‘Red Lion’, ASB and two lencultuur. Hillegom, The Netherlands.

1170 HORTSCIENCE, VOL. 26(9), SEPTEMBER 1991