Because the majority of ornamental plants produce flowers,many also cause allergies when the flowers release pollen grains into the air. For home gardeners concerned about allergies, choosing plants that are pollinated by insects or that produce relatively small amounts of airborne pollen allows the enjoyment of ornamental plants without the sneezing, stuffy noses, watery eyes, or scratchy throats of allergic reactions.
A study by the Allergy and Clinical Immunology Unit at Meir General Hospital in Israel, published in 1998, found that among the plants that produce the most allergy-causing pollen are flowers such as chrysanthemums, daisies, lilies, crocuses, hyacinths, roses and tulips. Beside producing pollen, the scent of such flowers can trigger allergies or an asthma attack. If allergies are a concern, the best option is to select decorative plants without a heavy floral or perfume scent.
Pollen-bearing trees also can increase cases of rhinitis. Oak is the deciduous tree most known for causing allergies. People allergic to pollen should also consider planting alternatives to pine, cedar, cypress, elm, mulberry, ash, birch, maple and sycamore in their home landscapes. Other trees that contribute to allergies, according to the Asthma & Allergy Foundation of America, are redwoods, palms, beeches, hickory trees, poplars, cottonwoods, willows, alders, aspens, box elders, pecans, walnuts and olive trees. English ivy and other ivy varieties that climb up trees and walls also can cause respiratory, as well as skin, allergies.
One option for allergy sufferers is planting female ornamental trees that bear seeds or fruit instead of producing pollen. Ash, poplar and mulberry are among these varieties. Another alternative is to grow fruit trees such as apple, pear, cherry, citrus and apricot, which are pollinated by insects and do not scatter as much pollen via the air.
While not pollen bearing, the ficus makes the list of ornamental trees that cause allergies because the sap on its leaves attracts dust, which is an irritant for many allergy sufferers. Typically found in homes and offices, the popular ornamental tree is also troublesome for people with latex allergies. A study by researchers at Saint-Pierre University Hospital in Brussels, Belgium, published in 2006 found ficus and yucca to be among the leading indoor ornamental plants that cause allergies.
Shrubs and Grasses
The Asthma & Allergy Foundation of America recommends people with allergies stay away from ornamental bushes and grasses that trigger allergy symptoms. Juniper and cypress are the top ornamental bushes that contribute to early spring allergies.
Certain types of decorative grasses, commonly used for accenting flower beds or landscaping borders, can wreak havoc on people suffering from allergies, hay fever or asthma. Ornamental grasses that are not kind to allergy sufferers are perennial rye, salt grass, fescue, sweet vernal, Bermuda grass, June grass, orchard grass, redtop grass, Johnson grass and timothy.