Plantago ovata 1

Plantago ovata

Plantago ovata is a weed native to the southwestern United States. It’s seeds have been used for food by native populations in Arizona and is a common source of psyillium – a dietary fiber found in products such as Metamucil.

Following a wet winter, Plantago ovata can be found growing wild in the desert and along road sides in the spring. It’s presence contributes signifcantly to South Mountain Park in Phoenix turning green in the spring.

Plantago ovata 2
Plantago ovata Ahwatukee, Arizona

Plantago ovata is related to English Plantain (plantago lanciolata) an important allergenic weed found in Europe, Asia and North America.

Annual Bluegrass (Poa annua)

Kentucky bluegrass is the most common turfgrass in the United States. Its use as a turf grass in Arizona is limited to the cooler parts of the state, typically at elevations about 5000 ft, although it may be used in some aggressively maintained golf courses at lower elevation. Annual bluegrass is a weedy variety that invades Bermuda grass lawns and fields in Arizona desert communities during the fall through spring. Birds and small animals eat the seed of the grass providing widespread distribution. Bluegrass pollen is highly allergenic and cross reacts with other cool weather grasses such as Rye grass and Timothy grass. It likes cool, wet conditions and will proliferate and take over lawns and sport fields if we have a rainy winter.

Alternaria alternata

Alternaria is a ubiquitous mold found almost everywhere in the country and is a normal agent of decay and decomposition as well as plant associated disease.  Alternaria pores are usually present in outdoor air throughout the year, frequently exceeding the number of pollen by 100- to 1000-fold or more, depending on environmental factors, such as water, nutrients, temperature, and wind.  In Arizona, Alternaria spore levels increase during the summer monsoon season and peak during the fall.  Airborne levels are affected by fall harvesting of crops and temperature inversion, trapping particulates including mold and pollen close to the ground.


Palo Verde (Parkinsonia microphylla)

Untitled design (10) (1)Palo Verde is one of the most common trees of the Sonoran Desert and is found throughout southern Arizona and southeastern California.  Starting in April, the Palo Verde produces a brite yellow flower that stands in contrast to it’s characteristic  green trunk and branches.  In late spring it is common to see the Palo Verde covered in yellow blossoms with a blanket of yellow at it’s base from dropped flowers.  It is this fact that makes the Palo Verde a bit of an allergy enigma.

As a general principle, plants that produce conspicuous and fragrant flowers do so to attract insects such as bees to distribute their pollen.  In addition, the pollen is typically heavy and sticky so that it sticks to the insects rather than being wasted blowing in the wind.  Wind pollenated plans on the other hand produce copious amounts of light pollen that easily catches a ride in a breeze, and often finds it’s way to the nose and eyes of allergy sufferers.   Palo Verde, although an insect pollenated tree, can cause allergy problems just because of the huge volume of flowers that fall to ground, dry, and then picked up by the wind

Johnson Grass

Johnson Grass flower

Johnson Grass is found in washes, along road sides and other areas where there is enough water.  Although it is an allergenic grass,  pollen counts in the Phoenix area tend to be low because of it’s sparse distribution.   It pollenates May through October.

Olive Tree (Olea europaea)

Untitled design (22) (1)The olive tree is native to the Mediterranean, Asia, and Africa and has been cultivated for it’s fruit for thousands of years.  It is a hardy, drought and disease resistant tree, well suited for the harsh conditions of the Sonoran desert.  It is an evergreen tree which can grow to 30 ft and has an attractive gray, often gnarled and twisted trunk gaining character with age.  Some trees are hundreds of years old.  The olive tree produces a small,  inconspicuous pale, white flower which is wind pollinated and produces volumes of airborne pollen in the spring.   Olive tree pollen is one of the most potent and sensitizing of the allergenic plants of Arizona.  Because of it’s association with severe springtime allergy symptoms, the city’s of Phoenix and Tucson have banned the planting of fruiting Olive trees since the 1960s.  More

Bermuda grass (Cynodon dactylon)

Bermuda Grass flower

Bermuda Grass flower

Because of it’s resistance to heat and drought, Bermuda grass is well suited for Arizona and the desert southwest.  Common Bermuda is propagated by seed and produces significant amounts of pollen. It is used extensively in school sports fields, parks, golf courses, and green belts.  Hybrid Bermuda grasses such as Tif and Midiron, are the result of mating common Bermuda grass with African Bermuda grass resulting  in a plant with a finer leaf texture and which does not produce pollen or seed.    These hybrid varieties are used in many home lawns and smaller fields.     In 1994, Phoenix passed the Airborne Pollen Ordinance which requires that Bermuda grass lawns be kept short to prevent pollen-producing seed heads (see picture)  from forming.  It pollenates May through October

Mulberry Tree (Morus Alba)

Mulberry Tree (Morus alba)

Mulberry Tree (Morus alba)

The Mulberry tree (also know as Fruitless Mulberry or White Mulberry)  is often cited in stories  relating how Arizona went from a favored destination for allergy sufferers to one of the worst places to live if you have allergies or asthma.   New Arizona residents moving in from the South and East preferred the stately, large-leaved, shade trees they left behind to the local desert varieties and so  thousands of Mulberry, Olive, and Ash trees were planted throughout the valley.   Spring tree pollen levels in Phoenix were fairly low 40-50 years ago but over the past 30 years,  pollen levels in Phoenix have skyrocketed and along with it,  the Phoenix allergy-misery level.   To stem the flood, Phoenix passed the Airborne Pollen Ordinance which restricted the planting of male Mulberry and Olive trees.  As a result, there are few Mulberry trees in the newer communities of Phoenix such as the Foothills in Ahwatukee, although there are enough established trees  in the valley to supply the rest of the area with pollen for many years ago come.

Pollination: February through April