Environment and allergic disease              Return to menu

Gardens Compatible with Respiratory Allergy in Southern and Central Arizona

Why bother with low allergy horticulture? It may seem unlikely that reducing the number of allergenic plants in a single garden would make a difference to a sufferer of allergic disease.   Nonetheless, it is important to limit the spread of allergenic plants because a collective effort by as many of us as possible could have a real impact on the levels of pollen in our atmosphere.  Eliminating allergenic plants close to dwellings can reduce symptoms of occupants who have allergic respiratory disease.  Pima County government has recognized this problem for many years and established ordinances to limit the pollen fromBermuda Grass , Olive trees and Mulberry trees.

We are planting new allergens.  Although many exotic imported species that are wind pollinated (e.g., Australian Saltbush, Atriplex semibacata) are not yet prevalent, they could become a real problem if their introduction into the landscape continues.  All species of Atriplex are very allergenic.  Jojoba, a native species, is wind pollinated and may also become a common allergen with its increasing popularity in landscaping.

Grass

• All species of grass are allergenic, with the exception of a few hybrids. 
• Bermuda grass (Cynodon dactylon) is the most frequent sensitizer in Southern Arizona.  Remove it from domestic gardens and from dirt alleys whenever possible, remembering that its roots must be killed by application of Roundup to actively growing grass in the summer to prevent regrowth.  Neglecting a Bermuda grass lawn by failing to water it will NOT kill it.  Nonflowering hybrid Bermuda grass, e.g. Tif, is available, but that lawn should be watched for contamination with wild Bermuda grass over time.  St. Augustine Grass also seldom seeds, but is poorly suited to Arizona conditions.
• Dichondra (not a grass) is a lawn substitute, but needs plenty of water and is good rabbit food.
• Buffelgrass is  an invasive and prevalent weed in Southern Arizona.  It could become a significant allergen in the future.

Weeds

• Not all weeds produce allergenic pollen. However, plants with inconspicuous flowers are usually undesirable in a garden and hence are called "weeds."  Inconspicuous flowers usually produce wind-borne pollen, which can cause allergy. 
• To rid your garden of summer weeds and winter weeds consult your local University Agricultural extension service.

Flowers, small plants and shrubs

• Brightly colored flowers that attract bees and other insects or humming birds are generally not allergenic.
• Triangle Leaf Bursage (Rabbit Bush, Ambrosia deltoidea) is very allergenic and should be removed
• Desert Broom (Baccharis sarothroides) is allergenic for some people and should be removed
• Regular trimming of large shrubs to remove allergenic flowers e.g. Privet, is important.
• Choose plants from the List of ground cover and flowers , List of shrubs and List of vines

Succulents and Cacti

• None of these produce wind-borne allergenic pollen - they are ideal for a low allergen, low water use garden.
• Choose from List of accent plants and cacti.

Trees

• Avoid planting wind pollinated trees near dwellings.
• Planting of Olive trees (excluding the Swan Hill and Wilson varieties) and Mulberry trees is illegal in Pima County.
• Bamboo and palms are related to grasses but are rarely allergenic in Arizona.  See List of palms.
• Choose trees from the List of trees .  Those species (trees and palms) in which selection of female plants is important pose a problem, because sex determination of the plant is impossible until it is large enough to flower.
• Fruit trees are not allergenic, but most nut trees are.
• Although citrus flowers are not allergenic, the fragrance from citrus trees can be irritating for asthma patients.

Regulations for Pollen Control in Pima County

            Control of pollen from Bermuda grass, Mulberry trees and Olive trees is regulated by General Ordinances in Title 7, Chapter 7.41 of the Pima County Code.

Establishing a Garden in Arizona
 
           Advice on establishing gardens in the desert that are environmentally responsible is available from the University of Arizona Garden Extension Services.

Additional Reading 
Ogren-Thomas, L.  Allergy-free gardening.   A revolutionary approach to landscape planning.  Ten Speed Press, Berkeley, 2000
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Disclaimer:   This site is for educational purposes only.  Any information that you have found in this web site is not intended to replace medical care or advice given to you by your own physicians. You should consider consulting your local medical library and other web sites for additional information. 

Comments and suggestions welcome!   Email: schumach@u.arizona.edu
Content Owner:  Michael J. Schumacher, MB, FRACP, The University of Arizona

Updated 2/2012