University of Vermont Extension System
Department of Plant and Soil Science

Commercial Ornamental Horticulture (COH) Leaflet 17

Perennials Research at the University of Vermont

Leonard P. Perry, Extension Associate Professor

Production systems: Marjorie Duarte (1984-5)

Objective: To study growth differences in field soil and containers in relation to fertilizers, and in type of sowing containers.

Seedling studies:

1. Seedling size is directly related to container size. Cell and pack sown seedlings were larger than plug sown seedlings.

2. Timing and environmental conditions for planting plugs into the field are crucial. Gypsophila and Heuchera had 80% and 60% mortality when planted in the field in July, but not when planted in May. Few losses occurred when planted into containers.

3. Overall growth was best from cells or packs.

4. Achillea, Gypsophila grew best in the field. Heuchera grew best in containers.

5. Achillea transplanted from plugs to cells were similar to those sown directly into cells.

6. With good germination, plugs planted directly to the field of final pot are the least expensive.

7. When plugs cannot be planted directly, or when the germination rate is low, transplanting from packs or plugs to cells is the most cost effective method and the most efficient use of greenhouse space.

Field Bed Studies:

1. Heuchera-- more growth produced at 1 oz actual Nitrogen/sq yd level than at 1/2 oz of 0 oz/sq yd levels.

2. Gypsophila, Achillea-- no significant response.

3. No significant differences between ground and raised beds (Windsor loamy sand).

Container studies:

1. Osmocote fertilizer-- no differences among media.

2. Granular fertilizer-- greatest response--peat, bark media, least response--soil medium

"So although container perennials cost more to produce (1 gal, $1.69) than field ones (2 yr, $1.10), as seems logical, the ultimate decision depends primarily on more factors than cost alone-- the type of customer and market, plants grown, soil available, cultural procedures possible and preferable, climate and availability and cost of labor."

Nutrition of Hemerocallis: Sinclair Adam, Jr. (1985-6)

1. In general for plants of Puddin, Pardon Me, Mary Todd, and Stella de Oro, levels of 300 to 800 ppm ammonium nitrate applied weekly result in good quality, saleable plants by 90 days (under our conditions). Overall, optimum growth was at 400 ppm, with 100 ppm needed for saleable plants.

2. Plants obtained larger weights, higher grades, and increased width of fans in the soil-based medium (versus soilless bark based).

3. Cultivars vary in nutrient uptake ability, with 3-4% tissue nitrogen a suitable range for favorable growth of Hemerocallis.

Spring Sickness of Daylilies: Chris Darrow (1990-1)

Spring sickness can be described as the distorted, twisted and malformed new growth, usually seen in the spring. It is not to be confused with brown streaks down the leaves--leaf streak, a fungal disease. Anything that injures new growth at or prior to emergence can cause spring sickness. This is usually cold, but could include chewing such as from insects, herbicides, or mechanical damage.

Overwintering Methods: Leonard Perry (1984-9)

Types of Covering Materials:

1. Lavender and dianthus showed no differences in plant survival ratings among covering treatments.

2. Cheiranthus and Heuchera had best winter survival when overwintered under 3 layers microfoam/1 layer white poly on top, or 2 layers white poly with 1 foot straw between (sandwich).

3. The most effective cover in moderating temperatures was the poly/straw sandwich.

4. The straw/poly sandwich resulted in better regrowth after overwintering for 14 out of 19 species, compared with no cover. Silver mound artemisia, Double Snowflake baby's breath, German statice and Dragon's Blood sedum had no differences, while Rustic Colors rudbeckia survived with no cover but did not when covered.

5. Mirafy (white geotextile material) provided up to 40 degreesF protection when used in 2 layers in an unheated, double layer white poly house.

Overwintering in Field or Container:

Potting in fall, versus leaving in the field and potting in spring, resulted in more growth for Double Snowflake baby's breath but less for Parker's Gold yarrow the following season.

Time of Covering:

Time of covering in fall is not as crucial as time of uncovering in the spring, with the earlier the better (Mar 1 - Apr 1).

Aster and Solidago Germplasm Evaluations: Leonard Perry (1990-4)

Over 100 species and cultivars of asters and over 40 of goldenrod were evaluated over several years for bloom color, time, potential uses and problems. Ratings were recorded for rust on New England asters and landscape value for the New York and dumosus cultivars.

Garden Phlox Mildew and Hardiness Ratings: (1991-3)

Over 35 cultivars were rated over 2-3 years at 2 sites for susceptibility to powdery mildew, and for hardiness in Vermont. Ratings were also taken on organic controls for White Admiral. Best control was from horticultural oil applied every two weeks, or baking soda sprayed weekly, with no difference seen from their combination applied every two weeks. Little effect was seen from increased spacing. Mulches provided the worst conditions and mildew.

Controlled Freezing of Perennials:Leonard Perry, Todd Herrick (1993- ongoing)

Over a dozen species and cultivars were frozen in chest freezers to certain temperatures to determine killing temperatures.

Return to Perry's Perennial Commercial Page

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. Lawrence Forcier, Director, UVM Extension System, Burlington, Vermont. University of Vermont Extension System and U.S. Department of Agriculture cooperating, offer education and employment to everyone, without regard to race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status.