Perennial beds and mixed borders


Herbaceous Perennials

Plant life cycles

Annual plants complete their life cycle in one growing season.

Biennial plants generally complete their life cycle in 2 growing seasons.

Herbaceous perennial plants live for 2 or more years and many can flower and set seed each growing season

Herbaceous perennial plants live 2 or more years and can have multiple flowering cycles during each growing season.

In cold climates many herbaceous perennials overwinter as basal rosettes or using underground overwintering structures.

In warmer moist climates most herbaceous perennials are evergreen, while natives of dry climates may retreat underground during the dry season.  

Many tender perennials are used as annuals where they are not hardy in the region.

Herbaceous perennials can provide color and texture in the landscape. They can be long lived and relatively low maintenance. There are many varieties and cultivars to choose from. Some like hosta, daylily, and iris may have 1000’s of named cultivars.

Hosta and Astilbe in a PSU campus bed

Perennial plant selection and production

Perennial plants are produced from seed, cuttings, or in some cases tissue culture. Seed propagated cultivars are generally less expensive but may be less vigorous, have smaller flowers, and be less uniform than vegetatively propagated plants.

Some seed propagated perennials are hybrids, but many are open pollenated selections. It can take years to develop a new seed propagated hybrid and bring it to market.

Clonal plant cultivars can be introduced to the market more quickly than seed propagated cultivars. 

Vegetative propagation may be easier for some perennial species that have complex dormancy requirements that must be met before the seed will germinate.

The Perennial Plant Association is a trade organization for perennial plant producers .

The perennial plant association names a plant of the year each year. 

These are generally excellent choices for professional and home landscapes. 

Information on production and use of each of these plants can be found on their website. Click on the heading above.

Forcing Herbaceous perennials:

Many perennials are forced into bloom out of their normal season for spring sales. Plants with flowers are generally easier to sell than vegetative plants so growers trick the plants into flowering in the spring. 

To force a plant to bloom you must first grow it to maturity, then provide the proper temperature and photoperiod. 

Because many plants in the garden center have been forced it is important that you know a plants true growth habit for proper garden design. If you buy a perennial in flower you can not be certain it will bloom at the same time in future years under natural conditions

Echniacea for example can be forced into bloom using long days.

Design of perennial beds

Designing with perennials can be more of a challenge than using annuals. Bloom times may be short and can vary greatly. Plant size and shape, both when small and the bed is new, and when mature, of each selected species must be considered. Plant form can vary within the growing season so companion plants may be needed for some species. Because the plants may be in the bed for years, bed preparation is critical. Security lighting may interfere with flowering or dormancy of some herbaceous perennials.


Answer these questions in the week 13 Canvas module

Go to the perennial plant association website and read about the perennial plant of the year for 2014. How are these plants used in the garden? How are they propagated and grown?

Use the internet to research the forcing requirements for purple coneflower.

Use the internet to find 3 or 4 appropriate annual or herbaceous perennial companions for the following perennials:

  1. Tulip
  2. Dicentra spectabilis
  3. Pennisetum setaceum rubrum


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