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Annuals

Annuals are plants that germinate, grow, bloom, set seed and die in one growing season, usually from spring to fall. Some annuals will self-sow and therefore reappear the following year. Based on their temperature tolerance, they are classified as hardy, half-hardy, or tender. Hardiness may vary within genera.

Annuals have the important role of adding color to a landscape and are available in wide ranges of textures, shapes and colors. They are easy to grow and relatively inexpensive plants. The disadvantage of annuals is that they must be purchased year after year and often require diligent deadheading and a mid-season cutting back to provide continuous bloom. Because of their continuous blooming, they also usually require supplemental water and fertilizer.

A good resource list of annuals is located on the University of Nebraska webpage, Annual Flowers for Nebraska. This page includes both common and botanical names, site requirements, height, color and planting information as well as comments about each plant. For general details about seeding, planting and maintaining annuals and suggestions for various uses, see Flowering Annuals: Characteristics and Culture from the University of Missouri Extension Service.

The hardiness of a plant is determined by the plant's resistance to cooler temperatures. Some annuals such as pansy (Viola x wittrockiana) will germinate and flourish in cooler temperatures and decline in the heat of the summer. Other annuals such as flowering tobacco (Nicotiana species) will show symptoms of chilling damage if exposed to cool temperatures. The following are characteristics and lists of hardy, half-hardy, and tender annuals. These lists are in no way conclusive, and the hardiness may vary somewhat based on the location in which an annual is planted.

The following are characteristics of hardy, half-hardy and tender annuals. The heading of each section is a link to a list of the specified annual plants.

Hardy Annuals
    Hardy annuals
  • Grown primarily for spring blooming;
  • May be late-season bloomers and bloom well in the cool, fall temperatures;
  • May be sown directly into the soil as soon as it is workable;
  • Germinate and thrive in cooler temperatures;
  • Usually retreat or even die off in the summer heat;
  • Many are self-sowing.

Half-hardy plants
    Half-hardy plants
  • Should be sown indoors;
  • Should be set out or planted when evening temperatures are 55° F and above;
  • Will tolerate some cooler temperatures;
  • Usually bloom well in late spring / early summer, fade during the heat of summer, and then may bloom again in early fall;
  • Some are self-sowing.

Tender annuals
    Tender annuals
  • Have no tolerance for temperatures below 55° F, and prefer 70° F day and night;
  • Bloom in the heat of summer (July - August);
  • Require a longer growing season, so should be started indoors and moved outside only when all danger of frost has passed;
  • Very few self-sow.

For more on proper plant selection based on site and plant characteristics, see Plant Elements of Design plant selection database.

Click on any of the following headings and link to chapters that explain care and maintenance of herbaceous plants.

Propagation
Starting Plants from Seed
Collecting and Saving Seed
Self-Sowing Plants
Transplanting Seedlings, Cuttings and Divided Plants
References

Staking, Supporting and Training Plants
Methods of Supporting Plants
Materials & Structures
Training to Improve Plant Health (FUTURE)
Training Plants for Ornamental Purposes (FUTURE)
References

Pruning
Cutting Back Plants
Deadheading and Pinching Back (FUTURE)

Mulching & Watering
Why Use Mulch?
Application of Mulch
Mulching for Weed Control
Mulching for Winter Protection
Mulching for Moisture Control
Organic Mulches
Synthetic Mulches
Watering Your Landscape
How to Determine the Frequency and Rate of Watering
Water Quality and its Effect on Plants
References

Nutrition, Fertilizers, and Compost
The Basics of Plant Nutrition and Fertilizers
Soils (FUTURE)
Compost (FUTURE)
Fertilizer: the Do's and Don'ts
Organic Fertilizers (FUTURE)
Inorganic Fertilizers (FUTURE)
Salt Tolerant Plants

Weed Management
Weed Identification and Lifecycles
Cultural Management Methods for Weed Control
Pruning for Weed Control (FUTURE)
Herbicides
Understanding Labels (FUTURE)
Alternatives to Chemical Herbicides (FUTURE)
References

Diseases and Insects
Diseases
Insects
Integrated Pest Management (FUTURE)
References


References:

Clemson University Extension, "Growing Annuals", HGIC-1152, Karen Russ and Bob Polomski. http://hgic.clemson.edu/factsheets/HGIC1152.htm

Iowa State University Department of Horticulture, "What is an Annual°", John VanDyk. Originally appeared in Horticulture & Home Pest News, April 26, 1996 issue, p. 59. http://www.ent.iastate.edu/ipm/hortnews/1996/4-26-1996/annie.html

Kansas City State University Research and Extension, Wyandotte County, "Drought-Tolerant Annuals", Pat Lawson. http://outreach.missouri.edu/extensioninfoline/lawn&garden/drought_annuals.html

Kansas City State University Research and Extension, Wyandotte County, "Annuals for Shade", Pat Lawson. http://outreach.missouri.edu/extensioninfoline/lawn&garden/annuals_shade.html

Kansas City State University Research and Extension, Wyandotte County, "Annuals for Sun", Pat Lawson. http://outreach.missouri.edu/extensioninfoline/lawn&garden/annuals_sun.html

Missouri University Extension, "Flowering Annuals: Characteristics and Culture", G6629, Ray R. Rothenberger. April 1, 1997. http://muextension.missouri.edu/xplor/agguides/hort/g06629.htm

Nebraska Cooperative Extension , "Growing Annual Flowers", G84-721-A, Donald Steinegger, Susan D. Schoneweis, Steve Rodie, and Anne Streich. Revised June 1999. http://www.ianr.unl.edu/pubs/horticulture/g721.htm

Nebraska Cooperative Extension , "Annual Flowers for Nebraska", G84-739-A, Anne Streich, Susan Schoneweis, Steve Rodie, and Dale Lindgren. Revised June 2001. http://www.ianr.unl.edu/pubs/horticulture/g739.pdf

Ohio State University Extension Master Gardener Manual, "Herbaceous Ornamentals: Annuals" Jack Kerrigan and Margaret Nagel. http://hcs.osu.edu/mg/manual/herbac4.htm

Rice, Graham, Discovering Annuals. Timber Press, Portland, Oregon. 1999.

University of Massachusetts, fact sheet #20, "Annuals". www-unix.oit.umass.edu

University of Minnesota Extension online publications, "Flowers - Culture". Various. http://www.extension.umn.edu/topics.html°topic=5&subtopic=151

University of Minnesota Extension, "Annuals - Planting in Spring", INFO-U publication #441, Deborah L. Brown and Beth Jarvis, 1999. http://www.extension.umn.edu/info-u/plants/BG441.html

University of Virginia Cooperative Extension, Virginia Tech and Virginia State Universities, "Perennials, Annuals, and Bulbs", October 1996. http://www.ext.vt.edu/departments/envirohort/monthlytips/august/noteaugh.html

Yockey, Terry L. Northern Gardening website, "Bulletproof Annuals", http://www.northerngardening.com/annuals.htm

 
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