COMMON ALLERGENIC TREES, SHRUBS AND WEEDS

Spring is in the air, as most allergy sufferers can tell you. In Orange County, the major cause of seasonal allergy is the pollen released by plants in the surrounding flora. Being aware of the common plants that cause allergy can help in scheduling activities so that the symptoms of allergy are at least less severe. Listed below are some common allergenic trees, shrubs and weeds common to Orange County and the rest of Southern California. In addition to the trees and shrubs listed, many others occur sporadically as ornamentals. TREES AND SHRUBS Type: Acacia Bloom: January-mid-summer Description: More than 20 species of acacia are currently grown locally as ornamentals, where they are commonly planted in yards and as visual screens along highways. Type: Box elder Bloom: March-April Description: This relative of the maple is used as a street and park tree. It has escaped from cultivation in some areas and is becoming established in the wild. Type: Chamise Bloom: May-June Description: One of the most abundant shrubs in the chapparal areas. Type: Alder Bloom: February-March Description: White alder is scattered throughout the stream valleys and on some mountain slopes. It is also used as a park tree. Type: Sagebrush Bloom: August-December Description: Many species of sagebrush occur in the wild and some are used as ornamentals in drier zones. Type: Scale Bloom: June-September Description: Many different species of scale (wingscale, shadscale, lenscale, allscale, spine scale) occur throughout Southern California. Lenscale is often planted as a hedge along the coast because of its resistance to salt water. Type: Eucalyptus Bloom: All year Description: More than 150 species of eucalyptus have been introduced in Southern California from Australia. Probably the most widely distributed (because it has escaped into the wild) is the towering blue gum eucalyptus. Type: Walnut Bloom: April-May Description: Probably the worst offender among the walnuts is the native California black walnut, which occurs on brushy hillsides throughout Southern California. English walnut and black walnut are occasionally planted. Type: Juniper Bloom: January-March Description: California juniper covers thousands of acres on the dry inner slopes of the mountain ranges and along the desert margins. Many other species are planted as ornamentals around homes, parking lots and other areas. Type: Mulberry Bloom: February-March Description: A popular ornamental tree and a major cause of urban and suburban allergies. Type: Olive Bloom: March-May Description: Widely planted as a dry land ornamental, olive trees are a primary cause of allergy. Type: Poplar/Cottonwood Bloom: February-April Description: Most areas of Southern California have one or more species of this group, and some are planted as ornamentals. Type: Oak Bloom: March-May Description: Numerous species of oak are either planted or native to the county. Type: Elm Bloom: February-March Description: Several species of elm have been planted as ornamentals. Some species flower in late summer, September to October. WEEDS Type: Ragweed Bloom: August-September Description: The scourge of hay fever sufferers is represented locally by false, western and slender ragweed. Giant and short ragweed, the common species of the eastern U.S., are not common here but their numbers are reportedly increasing annually. Type: Pigweed/Amaranth Bloom: June-November Description: This group, represented by redroot pigweed and Palmer’s amaranth, occurs most often in vacant lots, roadsides and the margins of cultivated fields. Type: Lamb’s quarters Bloom: June-October Description: Common weed of gardens, vacant land and roadsides. Type: Common plantain Bloom: May-November Description: Common weed in waste places and roadsides, especially in moist soils. Type: Dock/sorrel Bloom: March-June Description: Common weeds on vacant land and along roadsides. Yellow dock is usually the most common of the group. Type: Russian thistle Bloom: May-November Description: Found along the margins of cultivated fields, and on vacant land and roadsides. Often called tumbleweed. Source: Los Angeles chapter, Asthma and Allergy Foundation of America