Here is some general information on Alstroemeria from North Carolina State University Extension, which indicates they are generally hardy to 23 degrees.

The Royal Horticultural Society's A-Z Encyclopedia of Garden Plants, edited by Christopher Brickell (DK PUblishing, 1996) mentions Alstroemeria aurea and A. ligtu and their hybrids as being able to tolerate brief drops in temperature to 5 degrees Fahrenheit. Here are links to more information on these plants:
www.rhs.org.uk
seeds.thompson-morgan.com

Season All Season
Date 2006-12-08
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Here are some of the plants which are available in September: Achillea (Yarrow)
Alstroemeria (Peruvian lily)
Aster
Callicarpa bodinieri (beautyberry)
Cotoneaster (for foliage)
Dahlia
Echinops
Elaeagnus (foliage)
Eryngium
Heather
Hebe (flowers and foliage)
Helichrysum (straw flower)
Lavender
Acer (Maple: foliage)
Quercus (Oak: foliage)
Skimmia
Limonium (Statice)
Viburnum tinus

Here is a link to the Washington Park Arboretum web page of seasonal highlights.

Season All Season
Date 2007-03-03
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According to this University of California Davis Plant Sciences page on toxic plants, Alstroemeria is classified as possessing minor toxicity, meaning that ingesting the plant can cause gastrointestinal problems. Parts of the plant (not necessarily the blossoms) can also cause dermatitis if handled. See the following information on Alstroemeria from North Carolina State University Extension.

Rather than take any chances, I recommend restricting your decoration choices to edible flowers. A mixture of calendula, lavender, and violet blossoms, for example, might be an attractive option. North Carolina State University Extension also has an article on edible flowers.

Iowa State University Extension has useful guidelines on selecting edible flowers.

Season All Season
Date 2007-07-18
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