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  • Author or Editor: Robert E. Lyons x
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An historic feature of the JC Raulston Arboretum (JCRA) is to identify new and unusual ornamental plant materials for landscape use through an active program of observing landscape performance at the JCRA in Raleigh. Introduction of plant materials into commerce occurs primarily through programs conducted in concert with the North Carolina Association of Nurserymen and through a unique policy of “open access” for nurserymen. One program, The JC Raulston Selections Program, returns revenues to the general operations and maintenance functions of the JCRA; others are not revenue generating, and are provided as a service to the industry. To a lesser extent, the general public may participate in receiving new plants via a special program offered through JCRA membership. The JCRA is also an official trial garden site for the All America Selections program and seed companies. Elements of these introduction and evaluation programs will be discussed within the context of the past, present, and plans for the future for program maintenance and possible changes.

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An undergraduate “Service Course” generally presents principles of a particular discipline in an uncomplicated manner needing no prerequisites. The target audience is typically students majoring outside the service course department or undeclared majors. The primary motives behind service courses are recruitment from within the university, providing non-mjors with a broad appreciation for a discipline, and providing graduate students with classroom teaching/management experience. `The structure, dynamics, success, and adaptability of “Indoor Plants,” a Virginia Tech Horticulture service course enrolling approximately 400 students per year, will be discussed. Comparisons with other service courses will be made.

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Juvenility and flowering requirements of Chrysanthemum ×superbum Bergmans ex J. Ingram `G. Marconi' and `Snow Lady' were examined by growing plants under short days (SDs) and transferring them to long days (LDs) upon reaching specific true leaf stages. `G. Marconi' plants did not flower in continuous SDs and only sparse flowering occurred in plants transferred to LDs. `Snow Lady' plants transferred from SDs to LDs at the cotyledon stage flowered fastest from seeding (75 days) and had the fewest number of main stem leaves and total leaves (9 and 15, respectively) at the time of first flower. Plants moved from SDs to LDs at the 24 true leaf stage flowered 123 days after seeding and averaged 28 leaves on the main stem and 37 total leaves at the time of first flower. To examine apical floral initiation, plants were distributed between SDs and LDs following transplanting and five plants per treatment were sampled each week thereafter. Microscopic examination revealed floral initiation in plants sampled after just 1 week in LDs and, after 5 weeks, macroscopic terminal flower buds were present. Under SDs, apical floral initiation began after 5 weeks, yet, 9 weeks were required for floral initiation in all five plants sampled.

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To examine the effects of chilling and a limited inductive photoperiod (LIP) on flowering of Chrysanthemum superbum Bergmans ex J. Ingram `G. Marconi' and `Snow Lady', Coreopsis grandiflora Hogg `Sunray', and Coreopsis lanceolata L. `Early Sunrise', seeds were sown and plants were maintained in the greenhouse in short days (SDs) for 7 weeks, followed by 4 months of natural outdoor chilling for all plants except 10 of each cultivar, which remained in the greenhouse under SDs for the duration of the experiment. Upon return to greenhouse conditions, 10 plants of each cultivar were placed in SDs, all other chilled plants were placed in long-days (LDs) and subsequently transferred to SDs after receiving 6, 8, 10, 12, 14, 16, 18, 20, or 22 LD cycles. Ten chilled plants of each cultivar remained in LDs for the duration of the experiment. Continuous SDs without chilling resulted in 70%, 40%, 20%, and 10% flowering in `Snow Lady', `Early Sunrise', `Sunray,' and `G. Marconi', respectively. Chilling, followed by a return to continuous SDs, improved flowering in all cultivars compared to SDs without chilling. The number of LD cycles required for 100% flowering varied with cultivar. Ninety percent of the chilled `Early Sunrise' plants flowered with no LD cycles, and 100% flowering was produced by as few as six LD cycles. In `Snow Lady', 100% flowering occurred in chilled plants with no LD cycles and those receiving at least 10 LD cycles. With only six or eight LD cycles, 90% and 80% of these plants, respectively, still flowered. The percentage of `G. Marconi' and `Sunray' plants flowering ranged from 40% to 100% in the chilled treatments, with a general trend for more flowering with an increase in the number of LD inductive cycles. Continuous LDs following chilling resulted in as high or higher percent flowering than any other treatments (100% for `G. Marconi' and 90% for `Sunray'). The effects of LIP were evident in both Coreopsis cultivars but in neither Chrysanthemum superbum cultivar. There was a linear relationship between the number of LDs received and stem length at first flower in `Sunray' and `Early Sunrise'. In both cultivars, a reduction in stem elongation of about 10 cm occurred when plants received only 6 LDs compared to 22 LDs. The number of days from the start of LDs to first flower increased linearly as the number of LD cycles before the transfer back to SDs increased.

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Seeds of Celosia argentea L. `Pampas Plumes', Cosmos sulphureus Cav., Helianthus annuus L. `7111', and Zinnia elegans Jacq. `Gold Medal Mixture' were mixed with clean sand and hand-broadcasted over 60-ft2 (6.7-m2) plots at rates of 4 or 8 oz/1000 ft2 (122 or 244 g/100 m2). Each plot was either left undisturbed after sowing or the seed was raked into the soil surface. Estimated costs were calculated using the approximate number of seeds planted per plot and the cost per seed versus the number of plants reaching anthesis. Celosia and Zinnia bloomed for 42 days, Cosmos sulphureus for 28 days, and Helianthus for 12 days. Seeding rate had little effect on the number of plants maturing to flower in all species except Cosmos. There were no significant differences in number of weeds between treatments for any of the species. Raking the seed into the soil significantly improved germination at 2.5 and 5 weeks for Celosia, Cosmos, and Helianthus, but not for Zinnia. In Celosia, raking the seed into the soil more than doubled the number of plants maturing to flower, while in Cosmos the number reaching anthesis was not significantly altered by raking. The lowest costs per flowering plant occurred when the seed was raked into the soil for Celosia, Helianthus, and Zinnia.

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Juvenility and flowering requirements of Coreopsis grandiflora Hogg ex Sweet. `Sunray' and C. lanceolata L. `Early Sunrise' were examined by growing plants under short days (SD) and transferring them to long days (LD) upon reaching the designated true leaf stages. Neither cultivar flowered in continuous SD, and `Sunray' remained vegetative in LD. However, LD induced flowering in `Early Sunrise' plants in each leaf count treatment and the loss of juvenility was gradual, with most rapid flowering occurring when plants were transferred to LD at the 16 leaf stage. The limited inductive photoperiod (LIP) inhibited stem elongation of `Early Sunrise' plants in all LD treatments and selectively inhibited axillary flower bud development compared to plants grown in continuous LD. LIP did not affect scape length at first flower even though plant height was significantly diminished if given relatively few LD before transfer to SD. Height reduction was attributed to LIP inhibition of stem elongation with no significant loss of axillary flower bud potential.

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Histological and histochemical examination of floral initiation was conducted to determine the pattern of flowering in Rudbeckia hirta, a long-day (LD) plant. Plants were grown under 8-hour short days (SDs) until they had 14 to 16 expanded leaves. Half of the group of plants was moved to LD conditions consisting of natural daylength plus a 4-hour night interruption. Rudbeckia hirta had a pattern of differentiation in flowering similar to that reported in species requiring one inductive day for initiation. Rudbeckia hirta required 8 LDs for evocation and 18 LDs for completion of initiation. Involucral bracts initiated after 18 LDs, after which the receptacle enlarged and was capped by a meristematic mantle of cells signaling the start of development. Floret primordia did not initiate, even after 20 LDs. Increases in pyronin staining were observed in actively dividing cells of the procambium, leaf primordium, and corpus of the vegetative meristems. After 8 LDs, the pith rib meristem stained darkly, a result indicating the arrival of the floral stimulus. An increase in pyronin staining was also observed in the meristematic mantle covering the receptacle after 18 LDs, a result indicating increased RNA levels.

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Combinations of seeding rate, spacing, and weed control treatments were evaluated for their effect on the performance of the Virginia Tech transplanted meadow technique. The treatments consisted of seeding at 112 or 56 g·90 m−2; within-row transplant spacing of 30, 45, or 60 cm; and mulching, oryzalin application, or no weed control measures. Plant competition alone was insufficient, whereas oryzalin was the most effective for weed control but also reduced the plant stand and floral display. Mulch provided effective weed control with maximum floral display. Close transplant spacing within rows resulted in quick site coverage initially, but this advantage disappeared after 8 weeks compared to wider spacing. Seeding rate did not affect site coverage until the meadow reached maturity at 12 weeks. The lower seed rate allowed more lodging, resulting in a more open appearance and greater canopy light transmission. Chemical name used: 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin).

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