I'm interested in knowing which plants cause allergies because I experience allergies to pollen from grass and several trees. Did you know that repeated exposure to large amounts of allergenic pollen can cause you to develop an allergy to it, even if you don't have one now? Both those people who already have allergies and those who could develop allergies (that pretty much covers everyone!) might be interested in the following list. I went through Thomas Ogren's "Allergy-Free Gardening" book and picked out some of the plants with a rating of 9 or 10 on the OPALS scale. These are the plants that cause the most allergies. The entire list is huge, so I'm just including plants that are common to temperate climates like mine, plus a few that I remember from my Californian neighborhood. If you live in a mild climate, you'll just have to buy the book to find the worst allergy offenders for your area - including many types of allergenic palms and grasses. Actually, I recommend this book for every gardener and designer. The plants are listed alphabetically by latin name with common names in parenthesis. In many cases just the male forms are the offenders, as females don't produce pollen to cause allergies. Sorry I didn't do the italics thing but I just didn't have the patience for it on this long list.
After perusing the list, do you notice any plants that have given you allergy symptoms? Are there any that you might need to remove from your landscape? When we lived in California, I often walked past a long row of olive trees on my morning walks. By the end of the row, I usually had a headache, but didn't attribute the problem to the olive pollen until I reread Ogren's book and saw that olives are rated as a 10. I turn to his reference book as I'm considering new plants - especially trees - for my landscape. I'm willing to take medicine and put up with the sniffles in order to continue to enjoy time outdoors, but of course I'd like to reduce the problem by reducing pollen levels in my yard and community.