If they are to be used in more formal Pruning of Meadowsweet and Steeplebush landscapes, it is important to know how to manage them for optimal Kelly M. Stanton1, Sally S. Weeks2, Michael N. Dana1, and growth, form, and flowering. 1,3 Meadowsweet and steeplebush Michael V. Mickelbart produce summer flowers from new growth. Catchpole (1963) gives rec- ADDITIONAL INDEX WORDS. Spiraea alba, Spiraea tomentosa, hardhack, native plants, ommendations for pruning japanese growth, flowering spirea (Spiraea japonica), margitae spirea (Spiraea ·margaritae), and SUMMARY. Two native shrubs, meadowsweet (Spiraea alba) and steeplebush menzie’s spirea (Spiraea douglasii Spiraea tomentosa ( ), are currently grown for use in habitat restoration. Pruning var. ), all of which have could improve their form and encourage use in more formal gardens. Two seedling menziesii populations of each species were grown in the field or in containers outdoors. In similar growth and flowering habits Mar. 2009, plants were pruned to 3 or 15 cm or were left unpruned. By to meadowsweet and steeplebush. midsummer, there was no effect of pruning on plant height in field-grown plants. Catchpole (1963) recommended that However, pruning did eliminate lateral growth in field plants and, therefore, plants be pruned to ground level in improved overall form of the plants. Meadowsweet pruned to 3 cm had about half as April to promote the growth of new, many inflorescences as did meadowsweet pruned to 15 cm, with unpruned plants flower-bearing shoots. If they are not producing an intermediate number of inflorescences. Pruning container plants to 3 pruned, they accumulate dead wood, cm resulted in plants that were about half the height of unpruned plants, and total and flowering is reduced. Pruning biomass was greatly reduced. In general, plants that were pruned had fewer them to half-height still encourages inflorescences, although the total number of inflorescences in all plants was small. new growth but allows the develop- Pruning resulted in lower quality plant form in container plants. Species and seed sources within species responded similarly to pruning. Based on the data collected in ment of a larger plant. To date, this study, newly planted meadowsweet and steeplebush should be pruned to however, there are no similar pub- achieve good form in the first year. Despite the sometimes leggy growth habit in lished reports or recommendations containers, these species should not be pruned before growing out in the spring, or on pruning strategies for meadow- maximum growth and good form will not be attained. sweet or steeplebush. Pruning could eliminate apical dominance, resulting in shrubs with ative plants are a potential wide. They produce long-lasting ter- more branches and thus a fuller, more source of new plants for man- minal inflorescences on their vertical attractive appearance. Because the Naged landscapes. There is in- stems from mid-June (meadowsweet) inflorescences of meadowsweet and terest in gardening with natives not and mid-July (steeplebush) through steeplebush form on the stem tips, only for their novelty, but also to take August in the upper midwestern U.S. increasing the number of branches advantage of their adaptation to local (Swink and Wilhelm, 1994). Mead- could also increase the number of climates, to reflect regional differ- owsweet produces white flowers and flowers. ences, and to foster a connection with steeplebush has pale pink flowers. Meadowsweet and steeplebush nature (West, 2001). Native plants Both species send up numerous basal can tolerate mowing (White, 1955). can also be grown as an alternative stems, with little branching. Mead- In Quebec, when established plants to potentially invasive exotic land- owsweet is thicket forming (Meilleur of steeplebush were mown before scape plants. Consumers are willing et al., 1997). Meadowsweet has also spring growth was initiated, they to pay premium prices for an attrac- been found to be highly attractive to grew 30 cm by late July (Hay, tive garden featuring native plants insects that prey upon or parasitize 1958), indicating that these species (Helfand et al., 2006). insect herbivores (Fiedler and Landis, might respond well to severe pruning. The shrubs meadowsweet and 2007). These species tend to have asym- steeplebush are native to eastern North Steeplebush was used in the land- metrical, lateral growth in the nurs- America, and can be found growing scape as early as 1736 (Symes, 1983), ery. If these plants are to be sold in from the Gulf States into Canada (U.S. and meadowsweet and steeplebush retail nurseries, this appearance would Department of Agriculture, 2007). have potential as landscape plants. likely deter consumers from purchase. Meadowsweet and steeplebush grow Today, both species are used pri- If pruning after 1 year could im- to be 1 to 1.5 m tall and equally as marily in habitat restoration and prove plant appearance, these spe- less intensively managed areas where ciesmightbemoresuitableforretail We thank JFNew and Possibility Place Nursery for growth form is relatively unimportant. sales. Likewise, recommendations for supplying plants. Rob Eddy and Daniel Hahn assisted with container plant growth and maintenance. Jay Young and Nathan Linder assisted with setup and plot maintenance in the field. Mike Gosney provided Units technical advice and help. Meghan Honerlaw explained To convert U.S. to SI, To convert SI to U.S., statistics and SAS. multiply by U.S. unit SI unit multiply by 1 Department of Horticulture and Landscape Archi- 0.3048 ft m 3.2808 tecture, Purdue University, West Lafayette, IN 47907 3.7854 gal L 0.2642 2Department of Forestry and Natural Resources, 2.54 inch(es) cm 0.3937 Purdue University, West Lafayette, IN 47907 16.3871 inch3 cm3 0.0610 3Corresponding author. E-mail: mickelbart@purdue. 28.3495 oz g 0.0353 edu. (°F – 32) O 1.8 °F °C(1.8·C) + 32 700 • August 2010 20(4) early development of plant form in were transplanted into 1.5-L con- July 2009 and was dried to a constant the landscape might make these tainers on 11 Oct. 2008. The con- weight at 60 °C for determination of plants more attractive to landscapers tainers were overwintered outside dry weight. and homeowners. To determine suit- under mulch to a depth of at least DATA ANALYSIS. Data were ana- able pruning-management strategies 5 cm above soil level. The plants were lyzed using SAS (version 9.1; SAS for young meadowsweet and steeple- pruned 3 cm above media level or left Institute, Cary, NC). The significance bush, plants in containers and the field unpruned as a control. Pruning was of the differences among the treat- were pruned to various heights, and done on 24 Mar. 2009 immediately ments or seed sources was determined the resulting growth, form, and flow- after removing mulch from the con- from analysis of variance and Tukey ering of the plants were measured. tainers. Two weeks after pruning, 7 g tests were conducted with PROC of the 22N–2.2P–5K fertilizer (1.5 g GLM. The significance of the effects Materials and methods of N) was applied to each container. of the treatments on the frequencies of FIELD EXPERIMENT. All plants The plants were irrigated by hand as form rating was determined by using used in the experiments were supplied needed. Fisher’s exact test in PROC FREQ. as 15-inch3 plugs grown by commer- The experiment was a two-way cial nurseries from seeds germinated factorial arrangement on a random- Results in Spring 2008. Seeds of both species ized complete block design with 12 FIELD EXPERIMENT. Meadow- were collected by the nurseries in Will blocks. Each block contained two sweet and steeplebush produced ir- County, IL, and Jackson County, MI pruning treatments applied to plants regular and lateral growth in the (hereafter IL and MI, respectively). of both seed sources of both species. crowded conditions of the plug trays. Both seed sources of each species were MEASUREMENTS. Growth, flow- However, when plugs were planted used in the container experiments, but ering, and form ratings were collected in the field, most of the new growth only the IL source of steeplebush was for both experiments from 2 to 4 June produced in Summer 2009 was verti- used in the field experiment. and 20 to 24 July 2009. By early June, cal. Pruning to 15 or 3 cm did not The experiment was conducted most of the plants had produced affect the midseason height of plants at the Meigs Farm of the Throckmor- vigorous spring growth, but few had from different seed sources of either ton Purdue Agricultural Center in begun flowering. July measurements species (Table 1). However, because Tippecanoe County, IN (lat. 40.29 °N, were conducted when plants had much of the lateral growth was re- long. 86.88 °W). The soil type was attained their full size for the growing moved with pruning, the width of Drummer (silty clay loam) with a pH season and were blooming. pruned plants was less than unpruned of 6.9. Height was determined as the plants (Table 1). More of the pruned Plugs were planted on 28 Oct. vertical distance from the soil (field) plants were characterized as symmet- 2008, and they were pruned on 24 or media (container) level to the tall- rical compared with plants that were Mar. 2009. On 8 Apr. 2009, they est living part of the plant. For the not pruned (Table 2). Although the were fertilized with 12 g of 22N– field experiment, plant width was plants were smaller, they had a more 2.2P–5K 4- to 5-month controlled- measured in north-south and east- compact and full appearance. release fertilizer with micronutrients west axes, and the average was taken. The young plants used in this (2.6 g of N; Scotts, Marysville, OH).