Frequently Asked Grower Questions


It may not surprise you to find we get asked a lot of grower questions!  Below we have listed a number of the most frequently asked.  If you have one that isn't answered below, please contact us and one of our knowledgeable growing staff will be happy to talk shop and trade tips!  We also recommend checking out our Simple, Sensible, Solutions┬« Grower Guide(free by request) for more detailed information.


Are the plants I buy vernalized before they are shipped?

All bare root plants have been vernalized before they are shipped. 

Elle plugs are vernalized if they need to bloom that season. If they will bloom without being vernalized they might not be vernalized. All elle plugs should bloom the first season, except non-vernalized hosta.

What should a healthy bare root perennial look like?

Root should be firm, relatively dry, and light brown in color. Since most plants have been packed in advance for cold storage, appearance of light surface mold is not unusual. This is caused by the high humidity necessary in cold storage and is not harmful. It will disappear quickly or can be removed. Provide good air circulation. A preventative fungicide treatment is usually unnecessary.

How long will it take before my plants are ready for resale?

Please see our Timing Chart for details on finishing our bare root and plug perennials.

How safe is it to overwinter my perennials?

From our experience, overwintering success depends on having a well-rooted, established plant by the end of the growing season. It is important to keep the plant above freezing either with minimum heat or a layer of insulation, such as microfoam or straw and plastic. Do not cover plants before they are hardened off. Trim away any excess or dead foliage before covering.

Many perennial plants can be successfully transplanted in early fall. Properly overwintered, they will grow vigorously the following spring. As you may have experienced, however, factors such as soil moisture, temperature fluctuations, and root development in the container can affect a plant's survival. 

Since there are so many variables beyond our control, we do not guarantee survival of plants overwintered in containers or the ground. We do guarantee that you will receive healthy, vigorous plants that are true-to-name, on or very near the date we acknowledge.

Click here to read a detailed article on overwintering containerized perennials: Overwintering Info

What is Zone Hardiness?

The zone information provided on this website and all of our publications is strictly a guideline. Within any region there are variable conditons such as snow cover, moisture levels, microclimates, and many other factors which can alter the zone hardiness. We use the 1990 USDA Zone map in addition to personal experience as a basis for the information included in this website and all of our publications.

Zones listed in parenthesis (  ) on this website represent marginal hardiness with protection.  For example, a plant that is listed as zone (4)5-9 would be marginally hardy with protection in zone 4, but should be reliably hardy in zone 5.

What kind of light do my perennials need to be grown in?

For optimum rooting, most perennial varieties should be in full sun. However, for shade-loving plants such as Astilbe, Dicentra, and Hosta, a 50% shade cloth over the plants is recommended.

Could you please explain the difference between morning and afternoon sun?

Much like it is easier for humans to get a sunburn in the hot afternoon sun than in the morning, the same holds true for plants. Morning sun is much weaker in intensity than afternoon sun. Even though part shade is technically defined as 4-6 hours of direct sunlight, there is a huge difference between 4-6 hours of afternoon sun vs. 4-6 hours of morning sun. 

As a general rule, plants that prefer full shade to part shade need to be planted where they will have exposure only to morning sun or where they will receive no direct sunlight at all. 

Conversely, plants that prefer full sun need to be planted where they will receive an absolute minimum of 6 hours of direct afternoon sun, preferably much more.

When plants are sited in improper lighting conditions, they will tell you if you look closely. Some will stretch their stems and lean awkwardly towards the direction the sun is coming from. Others will not grow nearly as large as you would expect them to. Many will reduce their flower production or will not flower at all if there is not enough sunlight to produce buds. Some will just give up and die completely. Listen to your plants--they will tell you what they need!

What should the growing temperature be for perennials?

For spring planting, keep all perennials above freezing. Cold, wet conditions may cause plants to decline or rot. For best results, keep plants at 48-55 degrees F for 10-14 days after potting to promote root growth, and then grow at 55-60 degree F until finished. Lower temperatures stimulate root growth, yielding stronger plants. Maintain nighttime temperatures between 45-50 degrees F.

Lower temperatures may also be used to delay or suspend growth, while warmer temperatures help accelerate growth. In general, allow 6-8 weeks growing time in a cool greenhouse to finish off potted perennials. Good air circulation is also very important.

What size container should I use to pot my new plants in?

In General...

  • #1 Grade Bare Root Transplants should be potted into a 1-gallon container.
  • #2 Grade Bare Root Transplants should be potted into a 4-inch container.
  • 20 and 30ct plugs should be potted into a 1-gallon container.

For Proven Winners Perennials...

  • A recommended container size is listed for each Proven Winner Perennial we offer. 

For more information, please see our Timing Chart

How deep should I plant my Herbaceous Garden Peonies?

When potting up garden peonies, the eyes must be positioned 1.5 - 2 inches below soil level.

For more information on planting peonies, please see our Grower Tips for Peonies page

How deep should I plant my Tree Peonies?

When potting up bare root tree peonies, the following guidelines should be observed:

In the north the graft should be planted 2 inches below soil level.

In the south the graft should be planted 1 inch below soil level.

For more information on planting peonies, please see our Grower Tips for Peonies page

Should I use Fertilizer?

Use liquid fertilizers rather then incorporating granular or "slow release" fertilizers into the growing media.

What plants are good for division?

Numerous perennials can be divided for a greater return on investment. Root systems like those of Ajuga can be divided by hand, whereas others may require a sharp knife.

Smaller divisions can also be made and root pruned to fit a quart container.

Some bare root perennials that typically can be divided include:

  • Achillea
  • Ajuga
  • Anthemis
  • Artemisia
  • Asters
  • Belamcanda
  • Brunnera
  • Coreopsis
  • Dicentra (fern-leaf types)
  • Geranium
  • Hemerocallis
  • Hosta
  • Iris (most)
  • Leucanthemum
  • Liriope
  • Lysimachia clethroides and punctata
  • Nepeta
  • Penstemon
  • Phlox subulata
  • Rudbeckia
  • Sedums (some-usually low growing types)
  • Tanacetum
  • Thymus
  • Tradescantia
  • Viola

NOTE: Experience is important when dividing large numbers of perennials. Don't do anything on a large scale before initial testing is completed.

What kind of growing media should I use?

The media used to produce containerized plants must have several properties to provide adequate plant development. All media contains aggregates or components which consist of different materials and particle sizes. Some of the most commonly used aggregates include peat moss, bark, perlite and vermiculite. Mixing different components often provides the physical properties necessary for optimum plant growth. Components such as peat moss provide a media with excellent water holding characteristics. Other aggregates such as bark and perlite promote aeration and drainage.

We suggest a commercial bark-based soil-less mix. Most soil-less media contains 40-70% total pore space. After irrigating, the total porosity is usually between 10-30%. For perennials, look for a media with a total porosity of 50-60% which maintains 20-25% porosity after irrigating. Establishing a balance between the water-holding capacity and aeration is key to optimum plant growth. 

The pH of the media should be between 5.5 and 6.2 and the pH of the irrigation water is generally 5.4-7.0 for optimum perennial production.

For moisture-loving plants, we offer a few recommendations:

  1. Us a commercial mix with no bark.
  2. Use a larger pot size. (The plants will dry out less quickly)

Note: Astilbe, Ligularias and Cimicifuga in particular do not like to dry out.

What plants require dry soil conditions?

The following perennials need to be grown dry:

  • Aquilegia (Columbine)
  • Asclepias tuberosa (Butterfly Weed)
  • Corydalis lutea (Yellow Corydalis)
  • Echinacea (Coneflower)
  • Echinops (Globe Thistle)
  • Gaura (Wand Flower)
  • Gypsophila (Baby's Breath)
  • Iberis (Candytuft)
  • Lavandula (Lavender)
  • Oenothera missouriensis (Ozark Sundrop)
  • Perovskia (Russian Sage)
  • Platycodon (Balloon flower)
  • Stachys (Lamb's Ear)
  • Yucca (Adam's Needle)