Container-grown Herbaceous Perennials Research Articles

Influence of Plant Age on Cold Hardiness of Three Container-Grown Herbaceous Perennials

Abstract Overwintering container-grown perennial plants is often necessary during their production. Rooted vegetative cuttings potted at the beginning of the growing season and rooted vegetative cuttings potted at the beginning of the previous growing season, were exposed to−2,−5,−8,−11, and−14C (28, 23, 18, 12, 7F) in January then returned to a greenhouse kept at 3 to 5C (37 to 41F). In June, plants were assessed using a visual rating scale (1 = dead, 3–5 = increasing salable quality) and dry weight of foliage regrowth. For Geranium × cantabrigiense ‘Karmina’, studied for one year, age did not affect either rating or dry weight. For Sedum ‘Matrona’, studied for two years, age had no effect on dry weight but ratings were higher for two-year-old plants than one-year-old plants in the first year and higher for one-year-old plants than two-year-old plants in the second year. For Leucanthemum × superbum ‘Becky’, studied for two years, age affected both rating and dry weight, which were higher for one-year-old plants. Of the cultivars studied, overwintering one-year-old, container-grown plants resulted in more growth and higher quality than overwintered two-year-old plants.

(217) Preemergence Weed Control in Container-grown Herbaceous Perennials

During the 2005 season, three preemergence herbicides were applied to four container-grown herbaceous perennials and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicides and application rates were: 1) Pendimethalin (Pendulum 2G) 2.24, 4.48, and 8.96 kg/ha; 2) Trifluralin and Isoxaben (Snapshot 2.5 TG) 2.8, 5.6, and 11.2 kg/ha; and 3) S-metolachlor (Pennant Magnum 7.6 EC) 2.8, 5.6, and 11.2 kg/ha. Herbicides were applied to Coral Bells (Heuchera sanguinea), Hopflower Oregano (Origanum libanoticum), CORONADO™ Hyssop (Agastache aurantiaca), and SPANISH PEAKS™ Foxglove (Digitalis thapsi). Treatments were applied twice with 30 days between applications. Plants were evaluated for phytotoxicity after 1, 2, and 4 weeks after applying herbicide treatments. No phytotoxicity symptoms were apparent on any of the plants treated with Pendulum, and plant size (dry mass) was not affected. Snapshot resulted in visual phytotoxicity with Digitalis and Heuchera at the higher rates and also resulted in smaller plants. Pennant Magnum caused phytotoxicity at all rates in all plants and resulted in significantly smaller plants than the control. Weed control was very good with all herbicides, but did not control every weed.

Determination of Optimum Fertilizer Concentration and Corresponding Substrate Electrical Conductivity for Ten Taxa of Herbaceous Perennials

Little taxa-specific information is available regarding the nutrition needs of container-grown herbaceous perennials. The goal was to determine optimum fertilizer concentrations and corresponding substrate testing values for greenhouse production of 10 taxa. Astilbe chinensis (Maxim.) Franch. & Savat.`Purpurkerze', Campanula carpatica Jacq. `Deep Blue Clips', Coreopsis verticillata L.`Golden Gain', Gaura lindheimeri Engelm. & Gray, `Siskiyou Pink', Heucherasanguinea Engelm. `Mt St. Helens', Lamium maculatum L. `White Nancy', Penstemon ×hybridus Hort. `Sour Grapes', Perovskia atriplicifolia Benth. `Longin', Salvia nemerosa L. `Blue Hill', and Veronica × Hort. `Goodness Grows' were grown for 10 weeks with 15N–7P–14K at four rates (50, 150, 250, and 350 mg·L–1 N) of constant liquid feed. Substrate pH and soluble salts levels were measured weekly using the pour-through extraction method. In analysis of all taxa, most effects [quality, shoot dry weight, pH and electrical conductivity (EC)] varied by rate × taxa. Though higher levels of fertilizer produced the largest plants in some cases, satisfactory quality was also attained with a lower rate. Quality and pH were negatively correlated for a few genera but most showed no relationship. Results of this study indicate not all taxa tolerate increased fertilizer levels and that the herbaceous perennials studied could be grouped by nutritional needs. Furthermore, target ranges for EC can be developed based on dry mass and quality ratings.

(339) Preemergence Weed Control in Container-grown Herbaceous Perennials

During the 2004 season, preemergence herbicide was applied to 12 container-grown herbaceous perennials and woody plants and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicide and rates were: pendimethalin (Pendulum 2G) 908 g (label rate), 1816 g, and 3632 g/acre a.i. Herbicides were applied to lady's mantle (Alchemilla mollis), purple rock cress (Aubretia species), blue wild indigo (Baptisia australis), pink pussytoes (Antennaria dioica var. rosea), common sneezeweed (Helenium autumnale), redhot poker (Kniphofia uvaria), showy goldenrod (Solidago speciosa), heartleaf foamflower (Tiarella cordifolia), lavender (Lavendula angustifolia), blue flax (Linum perenne), catmint (Nepeta ×faassenii), and hen and chicks (Sempervivum tectorum). At 32 and 117 days after application, plants were evaluated for phytotoxicity. No phytotoxicity symptoms were apparent on any of the plants tested. Weed control was good in most cases with this herbicide but it did not control all weeds. Increasing the rates from 1× (label rate) did not significantly improve weed control.

Preemergence Weed Control in Container-grown Herbaceous Perennials

During the 2003 season, preemergence herbicide was applied to twelve container grown herbaceous perennials and woody plants and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicide and rates were: Flumioxazin (Broadstar) 113.5 g (label rate), 227 g and 454 g a.i./A. Herbicides were applied to Buxus microphylla `Winter Gem', Cytisus purgans `Spanish Gold', Festuca ovina glauca `Elijah Blue', Hakonechloa macra `Aureola', Lonicera tatarica `Arnold Red', Pachysandra terminalis `Green Sheen', Hydrangea arborescens `Annabelle', Mahonia aquifolium, Phalaris arundinacea `Picta', Carex buchananii, Cerastium tomentosum, and Achillea millefolium `Red Beauty'. Weed control was excellent at all rates and controlled at least 99% of all weeds. No phytotoxicity symptoms were apparent on Mahonia, Buxus, Cytisus, Festuca, Hakonechloa, Pachysandra or Phlaris. Phytotoxicity resulted on some of the other plants. Carex had smaller plants (dry weights) at all rates. Cerastium had severe phytotoxicty at the 227 g and 454 g rates and moderate stunting at the recommended label rate, 113.5 g. Hydrangea became chlorotic and stunted at the 113.5 g rate and some fatal toxicity ocurred at the 227 g and 454 g rates. Phytotoxicity resulted on Lonicera at all rates and ranged from mild chlorosis in leaf veins (113.5 g rate) to plant death (454 g rate). Achillea at the 113.5 g rate only resulted in stunted plant growth while the 227 g and 454 g rates resulted in severe phytotoxcity and plant death.

221 Preemergent Weed Control in Container-grown Herbaceous Perennials

During the 1999 season, preemergent herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Oxyfluorfen + Pendimethalin (Scotts Ornamental Herbicide II) 3 and 6 lb ai/A, Napropamide (G) (Devrinol) 3 and 6 lb ai/A, Oryzalin (Surflan) 2 and 4 lb ai/A, Oxadiazon (Ronstar) 4 and 8 lb ai/A, Oxyfluorfen + Oryzalin (Rout) 3 and 6 lb ai/A, Prodiamine (Barricade) 0.65 and 1.3 lb ai/A, Pendimethalin (Scotts Ornamental Weedgrass Control) 2 and 4 lb ai/A, Trifluralin (Treflan) 4 and 8 lb ai/A. Herbicides were applied to Penstemon mexicali `Red Rocks'™, Osteospermum barberiae compactum `Purple Mountain'™, Gazania linearis `Colorado Gold'™, Agastache rupestris, Diascia integerrima `Coral Canyon'™, and Zauschneria arizonica. All plant and herbicide combinations did not result in any significant decline in plant growth. All herbicides provided good weed control.

264 Identification and Characterization of Overwintering Methods for Container-grown Herbaceous Perennials

A survey was conducted to identify and characterize the effectiveness of overwintering methods used to protect container-grown herbaceous perennials in USDA hardiness zones 3 through 8. Survey questionnaires were sent by first-class mail on 20 Aug. 1996 to 634 firms involved in growing and/or selling container-grown herbaceous perennials identified from the Perennial Plant Association Membership Directory. Completed questionnaires were received from 293 individuals (46.2% response rate) in 38 states, the District of Columbia, and six Canadian provinces. Survey participants reported using several overwintering methods: structureless systems (71.0%), polyhouses (52.9%), polyhouses with inflated double polyethylene covers (30.7%), and low-profile polyhuts (12.3%). Over three-fourths of the respondents (78.8%) said their winter protection methods resulted in minimal to no plant loss (0-10%). Only 53 respondents (18.1%) reported losses >10%. The most frequently cited reason for plant loss across all hardiness zones was excessive moisture inside the overwintering environment (50.2%). Equal percentages (33.4%) indicated low temperatures and damage from animals as the next most likely factors responsible for plant loss. Respondents identified, in descending order, Iris, Delphinium, Lavandula, Papaver, and Lupinus as the five genera most difficult to overwinter.

018 Preemergent Weed Control in Container-grown Herbaceous Perennials

During the 1998 season, preemergent herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Napropamide (Devrinol 10G), 0.72 and 1.44 kg a.i./ha; Oryzalin (Surflan 40AS), 0.36 and 0.72 kg a.i./ha; Oxadiazon (Ronstar 2G), 0.72 and 1.44 kg a.i./ha; Oxyfluorfen + Oryzalin (Rout 3G), 0.54 and 2.16 kg a.i./ha; Oxyfluorfen + Pendimethalin (Scott's OH II), 0.54 and 1.09 kg a.i./ha; and Trifluralin (Treflan 5G), 0.72 and 1.44 kg a.i./ha. Herbicides were applied to Phalaris arundinacea `Picta', Scabiosa caucasica, Sedum × `Autumn Joy', Pennisetum setaceum `Rubrum', Salvia argentea, Penstemon × mexicali `Red Rocks', Osteospermum barberiae v. compactum `Purple Mountain', and Gazania linearis `Colorado Gold'. Phytotoxicity symptoms (visual defects) were apparent with Napropamide on Phalaris (at both rates) but recovered by the end of season. All herbicides provided good weed control.

Preemergent Weed Control in Container-grown Herbaceous Perennials

During the 1997 season, preemergent herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Napropamide (Devrinol 10G), 0.72 and 1.44 kg a.i./ha; Oryzalin (Surflan 40AS), 0.36 and 0.72 kg a.i./ha; Oxadiazon (Ronstar 2G), 0.72 and 1.44 kg a.i./ha; Oxyfluorfen + Oryzalin (Rout 3G), 0.54 and 2.16 kg a.i./ha; Oxyfluorfen + Pendimethalin (Scott's OH II), 0.54 and 1.09 kg a.i./ha; and Trifluralin (Treflan 5G), 0.72 and 1.44 kg a.i./ha. Herbicides were applied to Phalaris arundinacea `Picta', Scabiosa caucasica, Sedum spectabile `Autumn Joy', Pennisetum setaceum `Rubrum', and Salvia argentea. Phytotoxicity symptoms (visual defects and lower dry weights) were apparent with Napropamide on Phalaris (at both rates). All herbicides provided good weed control.

Pre-emergent Weed Control in Container-grown Herbaceous Perennials

During the 1996 season, pre-emergent herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Napropamide (Devrinol 10G), 0.72 and 1.44 kg a.i./ha; Oryzalin (Surflan 40AS), 0.36 and 0.72 kg a.i./ha; Oxadiazon (Ronstar 2G), 0.72 and 1.44 kg a.i./ha; Oxyfluorfen + Oryzalin (Rout 3G), 0.54 and 2.16 kg/ha; Oxyfluorfen + Pendimethalin (Scott's OH II),0.54 kg a.i./ha; and Trifluralin (Treflan 5G), 0.72 and 1.44 kg a.i./ha. Herbicides were applied to Campanula carpatica, Dianthus gratianopolitanus, Gaillardia × `Baby Cole', Penstemon × `Husker's Red', and Phlox subulata `Emerald Blue'. Phytotoxicity symptoms (visual defects and less height) were apparent with Oryzalin on Penstemon (at both rates) and on Phlox (0.72 kg a.i./ha). Weed control was significantly less with Trifluralin and Napropamide when compared to the other herbicides.

Preemergent Weed Control in Container-grown Herbaceous Perennials

Herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. During the 1995 season six preemergent herbicides [(in kg·ha–1) Napropamide (Devrinol 10G), 4.5 and 9.1; Isoxaben (Gallery 75DF), 1.1 and 2.3; Oxadiazon (Ronstar 2G), 4.5 and 9.1; Oxyfluorfen + Oryzalin (Rout 3G), 3.4 and 13.6; Oryzalin (Surflan AS), 2.8 and 4.5; and Trifluralin (Treflan 5G) 4.5 and 9.1, were tested on Callirhoe involucrata, Delosperma nubigenum, Dendranthemum ×morifolium `Jennifer', Festuca cinerea `Sea Urchin', and Gypsophila paniculata `Fairy's Pink'. Isoxaben (both rates) resulted in visual phytotoxicity symptoms and sometimes death to Dendranthemum. Oxadiazon (9.1 kg·ha–1) and Oxyfluorfen + Oryzalin (both rates) resulted in plant chlorosis and necrosis to Delosperma soon after herbicide application, but plants outgrew herbicide damage. Napropamide (both rates), applied to Delosperma, resulted in less dry weight when compared to some of the other herbicide treatments. Oryzalin (4.5 kg·ha–1) resulted in visual phytotoxicity and less plant dry weight to Festuca. Data analysis revealed no significant differences in Callirhoe and Gypsophila. In general, most herbicides controlled weeds effectively.

Isoxaben and Isoxaben Combinations for Weed Control in Container-Grown Herbaceous Flowering Perennials

Abstract Gallery DF (isoxaben), Snapshot DF (isoxaben + oryzalin), and Snapshot TG (isoxaben + trifluralin) were applied to four species in 1991 and to nine species in 1992 of container-grown herbaceous flowering perennials to evaluate efficacy, phytotoxicity, and effect on plant growth. Surflan AS (oryzalin) and Treflan 5G (trifluralin) were used as standard herbicide checks. Gallery was applied at 0.56, 0.84, and 1.12 kg ai/ha (0.5, 0.75, and 1.0 lb ai/A). Snapshot DF and Snapshot TG were applied at 2.8, 4.2, and 5.6 kg ai/A (2.5, 3.75, and 5.0 lb ai/A). Coreopsis was not affected by any herbicide treatment either year. Painted daisy was injured by all treatments except Snapshot TG at 2.5 lb ai/A and Treflan. Gallery at 1.12 kg ai/ha (1.0 lb ai/A) and Snapshot DF at 5.6 kg ailha (5.0 lb ai/A), injured all species except coreopsis and hibiscus. Surflan injured gloriosa daisy (1991 only), chrysanthemumhollyhock, hibiscus, and painted daisy. Snapshot TG applied at 5.6 kg ai/A (5.0 lb ai/A) injured hollyhock. Height of coreopsis, shasta daisy, gloriosa daisy, and columbine was not affected or only slightly reduced by any treatment. Hollyhock, hibiscus, painted daisy, and chrysanthemum were generally shorter in containers treated with Snapshot DF at 4.2 kg/ha or higher rates.

Controlled Freezing of Twenty-three Container-grown Herbaceous Perennials

Abstract Twenty-three containerized herbaceous perennials were acclimated to ambient outdoor temperature and photoperiod until November 19, when they were moved into a greenhouse and held at 3C (37F) until February 15. At that time, plants were exposed for 30 minutes to a range of subzero temperatures, and returned to the greenhouse for forcing. Plants were rated for survival and salability following 6 weeks regrowth at 15C (59F), using a subjective scale of 1 to 5 (1 = worst, 5 = best, 3 and above considered salable). Of the 23 perennials studied, 15 survived after exposure to at least-8C (18F), however, 40% of the species and cultivars surviving at this temperature sustained a level of injury which rendered them unsalable. Most plants were rated salable at treatment temperatures 3 to 6 degrees warmer than their respective lowest survival temperatures (LST's). Phlox ‘Chattahoochie’, Phlox ‘Morris Berd’ and Tiarella ‘Laird of Skye’ remained salable after exposure to —11C (12F). Campanula takesimana, Heuchera americana ‘Dales Strain’, Penstemon fruticosus ‘Purple Haze’, Rosmarinus officinalis ‘Arp’, Tiarella ‘Running Tapestry’, and Tiarella cordifolia ‘Slick Rock’ remained salable after exposure to-8C (18F). Erodium reichardii ‘Roseum’, Hebe macrocarpa ‘Margaret’, and Verbena ‘Homestead Purple’ remained salable after exposure to-5C (23F). Only the unfrozen controls of Houttuynia cordata ‘Chameleon’ and Thelypteris kunthii remained salable. Treatment means for Ceratostigma plumbaginoides were not significantly different and all 6 Hibiscus cultivars (‘Blue River II’, ‘Disco Belle Pink’, ‘Disco Belle Rose Red’, ‘Disco Belle White’, ‘Lord Baltimore’ and ‘Southern Belle’) failed to survive any of the temperature treatments. In general, plants showed a gradual decline in salability with decreasing temperatures.

Preemergent Weed Control in Container-grown Herbaceous Perennials

Herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control and phytotoxicity. During the 1994 season, seven preemergent herbicides, napropamide (Devrinol) at 4.5 and 9.1 kg·ha–1, metolachlor (Pennant) at 4.5 and 9.1 kg·ha–1, isoxaben (Gallery) at 1.1 and 2.3 kg·ha–1, oxadiazon (Ronstar) at 4.5 and 9.1 kg·ha–1, oxyfluorfen + oryzalin (Rout) at 3.4 and 13.6 kg·ha–1, oryzalin (Surflan) at 2.8 and 4.5 kg·ha–1, and trifluralin (Treflan) at 4.5 and 9.1 kg·ha–1, were tested on Aquilegia caerulea `McKana's Giant', Digitalis purpurea, Gaillardia aristata, Limonium latifolium, and Veronica spicata. Isoxaben (both rates) resulted in visual phytotoxicity symptoms and death to Digitalis. Metolachlor (both rates) resulted in plant death to Veronica. Pennant (both rates), when applied to Limonium, resulted in stunted growth. Aquilegia and Gaillardia were not adversely affected. Most herbicides controlled both dicot and monocot weeds effectively.

Preemergent Weed Control in Container-grown Herbaceous Perennials

Herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control and phytotoxicity. During the 1994 season, seven preemergent herbicides, napropamide (Devrinol) at 4.5 and 9.1 kg·ha–1, metolachlor (Pennant) at 4.5 and 9.1 kg·ha–1, isoxaben (Gallery) at 1.1 and 2.3 kg·ha–1, oxadiazon (Ronstar) at 4.5 and 9.1 kg·ha–1, oxyfluorfen + oryzalin (Rout) at 3.4 and 13.6 kg·ha–1, oryzalin (Surflan) at 2.8 and 4.5 kg·ha–1, and trifluralin (Treflan) at 4.5 and 9.1 kg·ha–1, were tested on Aquilegia caerulea `McKana's Giant', Digitalis purpurea, Gaillardia aristata, Limonium latifolium, and Veronica spicata. Isoxaben (both rates) resulted in visual phytotoxicity symptoms and death to Digitalis. Metolachlor (both rates) resulted in plant death to Veronica. Pennant (both rates), when applied to Limonium, resulted in stunted growth. Aquilegia and Gaillardia were not adversely affected. Most herbicides controlled both dicot and monocot weeds effectively.

Evaluation of Structureless Overwintering Systems for Container-Grown Herbaceous Perennials

Abstract Five structureless overwintering systems were evaluated for temperature moderation and protection of 18 container-grown herbaceous perennials from low-temperature injury. Two light-excluding treatments; 30 cm (1 ft) of straw between two layers of 4-mil white polyethylene and 18 cm (7 in) deep, in-ground beds protected with one layer of 4-mil white polyethylene and 30 cm (1 ft) of woodchips, provided the greatest moderation of winter low and early spring high temperatures, but also resulted in severe etiolation. A bonded white polyethylene/microfoam overwintering blanket (thermoblanket) with translucent properties provided comparable plant survival percentages despite dramatic temperature extremes recorded beneath this cover and, in late winter, created an environment conducive to moderate plant growth without formation of etiolated tissue.

EVALUATING STRUCTURELESS OVERWINTERING SYSTEMS FOR CONTAINER-GROWN HERBACEOUS PERENNIALS

A major limiting factor in producing container-grown herbaceous perennials is low-temperature injury to cold sensitive roots and crowns during above ground winter storage. Growers and retailers of these plants understand the need for protection systems, yet specific recommendations are unavailable. The ability of several structureless systems to moderate temperature and protect 16 species of container-grown herbaceous perennials from low-temperature injury was investigated. Two light-excluding treatments consisting of 30 cm of straw between 2 layers of 4 mil white copolymer, and 18 cm deep in-ground beds protected with 1 layer of 4 mil white copolymer and 30 cm of woodchips provided the greatest moderation of winter low and early spring high temperatures but resulted in severe etiolation among test plants, A bonded white copolymer-microform overwintering blanket with translucent properties provided comparable plant survival, and prevented etiolated growth allowing plants to grow rapidly after uncovering, despite dramatic temperature extremes observed beneath this cover.

Overwintering Container-grown Herbaceous Perennials in Northern Regions

Abstract A 3 year study was initiated to evaluate the survival of several species of container-grown herbaceous perennials with various overwintering techniques. Although species reacted individually to overwintering covers, those with white reflective surfaces generally provided adequate protection. Straw, non-reflective Plantfoamss™, or no cover usually resulted in large losses. Container medium temperatures were 4° to 7°C (8° to 15°F) degrees warmer than surrounding air temperatures, with a “sandwich” of 30 cm (1 ft ) fluffed oat straw between layers of white polyfilm providing the least medium temperature fluctuation (3°C or 6°F with ambient fluctuation of 16°C or 34°F), and the most temperature moderation (1°C or 34°F with ambient −16°C or 3°F). Uncovering plants later than the first week in April occasionall y resulted in plant losses.

Preemergent Weed Control in Container-grown Herbaceous Perennials

Abstract This study was conducted to evaluate several preemergence herbicides for weed control, effects on plant growth, and phytotoxicity to container-grown herbaceous perennials. Surflan (Oryzalin) was applied at 0, 2.24, 4.48, 6.72 kg ai/ha (0, 2, 4, 6 lb ai/A), Ronstar (Oxadiazon) at 0, 4.48, 8.96, 13.44 kg ai/ha (0, 4, 8, 12 lb ai/A), and Rout (Oxyfluorfen + Oryzalin) at 0, 3.36, 6.72, 10.08 kg ai/ha (0, 3, 6,9 lb ai/A) to container-grown Ajuga reptans atropurpurea L. (carpet bugle), Campanula garganica major (Ten.) Fiori (bellflower), and Liatris spicata (L.) Willd. (spike gayfeather). Additionally, Devrinol (Napropamide) and Treflan (Trifluralin) were each applied at 0, 4.48, 8.96, 13.44 kg ai/ha (0, 4, 8, 12 lb ai/A) to Astilbe × arendsii Arends. (false spirea) and Dicentra spectabilis (L.) Lem. (bleeding heart). Plants were grown in 2.54 1 (#1) containers in a medium of sand, topsoil, and sphagnum peat (1:1:1 by vol). Weed control was acceptable with all herbicides except Surflan at 2.24 kg ai/ha (2 lb ai/A) which did not control shepardspurse. Surflan applied at either 4.48 (41b ai/A) or 6.72 kg ai/ha (61b ai/A) rate resulted in phytotoxicity of carpet bugle, while the 6.72 kg ai/ha rate (6 lb ai/A) significantly reduced plant growth.