10 Worst Plants for Your Allergies

If you're sneezing, it's probably because allergy season is here. Itchy eyes, runny nose and a general feeling of misery afflict those who are unlucky enough to suffer from allergies.

Whether you have allergies is pretty much a genetic roll of the dice. You'll probably have allergies if your parents had allergies, but it's not a given. Basically, allergies are the result of a hypersensitive immune system. Your immune system attacks substances it mistakenly identifies as harmful -- and then the symptoms kick in.

When we talk about being allergic to plants, we're talking about being allergic to the plant's airborne pollen. Certain plants are more likely to trigger hay fever. Click ahead to learn about 10 of the worst offenders.

10: Ragweed

Ragweed might be the most allergenic plant out there. Seventy-five percent of people with pollen allergies are allergic to ragweed. To make matters worse, the plant is extremely common -- there are 17 types of ragweed in North America. Ragweed releases huge numbers of pollen grains into the air. If you live in the United States and you want to escape it, head New England or West Coast.

Ragweed facts:

Appearance: It grows no more than 2 feet high, with pointy leaves and clusters of greenish-yellow blooms. The flowers open downward to release pollen into the wind.
Peak time: It pollinates in summer and fall.
Location: You'll find it growing along roadsides, in fields, along riverbanks, in vacant lots and in rural areas. It likes to grow where soil is disturbed -- by water streams, salting of roads or cultivation. It's easily overgrown by other plants, but if it finds disturbed soil, it will take root and thrive.

9: Bermuda Grass

Bermuda grass is native to Africa, but is now established in most of the world. In the United States it's called Bermuda grass because it's believed to have been brought to the United States from Bermuda. Bermuda grass is popular for lawns and golf greens because it's resistant to foot traffic. It spreads by both root and seed, and it's flowering seed causes allergies. If you keep your Bermuda grass very closely mown, it's less allergenic.

Bermuda grass facts:

Appearance: Bermuda grass has short bluish-green leaves. The leaves turn brown during cold weather, since the grass is more of a warm weather plant. Its flowering stems can grow to more than a foot tall, but it's usually shorter -- with 4- to 6-inch long seedheads.
Peak time: Bermuda grass flowers in the spring through October.
Location: You'll find Bermuda grass just about anywhere. Like we said earlier, it's a favorite for golf greens, lawns and pastures.

8: Maple

The maple tree -- more specifically, the ashleaf maple or box elder tree -- is another plant that produces potent allergens. Other species of maple, like the red, silver, and sugar varieties, also trigger allergies. But the ashleaf maple is the worst offender. Only the male trees produce the pollen allergen. These trees favor a lot of light and rich, moist soil. Maples are popular for their timber, sugar and syrup.

Maple facts:

Appearance: Ashleaf maples are small- to medium-sized trees. They grow from 30 to 50 feet high, with a typical trunk diameter of about 4 feet. Blooms grow in small bunches, have no petals, and are greenish-yellow.
Peak time:Maple trees flower and release pollen in the early spring.
Location: Maples are mostly found along streams and in the woods of the Eastern United States and Canada, and midwestern North America.

7: Mountain Cedar

The mountain cedar, a type of juniper tree, is very common in the hills of Texas, Oklahoma mountains, and parts of the Ozarks. The tree spreads lots of pollen and therefore spreads aggressively. In fact, in Texas, there's much controversy about managing the tree's growth. People opposed to the cedar trees point out that the trees absorb a lot of ground water, especially in areas that have issues with water shortages. Also, their pollen production is so large that the trees prevent many people from enjoying outdoor activities.

Mountain cedar facts:

Appearance: These trees are usually pretty small and gnarled, with tiny leaves. The leaves release pollen. Then bluish, berrylike cones appear in the summer.
Peak time: Mountain cedars flower in winter, usually December and January.
Location: You'll find mountain cedars in Arkansas, Missouri, some parts of New Mexico, Oklahoma, and of course, Texas.

6: Rye Grass

All grasses are allergenic, but some are more allergenic than others. Grasses release pollen when they flower, which is why it helps to keep grass cut sort. Rye grass is doubly rough on people with allergies because it's also prone to mold. It's a popular choice for lawns, and is also found in pastures, meadows and on roadsides.

Rye grass facts:

Appearance: Rye grass grows in bunches, with flat or slightly rolled leaf blades. The grass can be anywhere from 1 to 10 inches long, depending on whether or not it's maintained. When it flowers, you'll see the blooms on stalks that are 2 to 6 inches tall.
Peak time: Rye grass flowers in the summertime, from around June to August.
Location: You'll see a lot of rye grass in the northern United States -- it likes dry and cool temperatures.

5: Elm

Elm trees are widespread throughout the United States. They're valued for their wood and their shade; plus, the fruit they drop feeds wildlife. Between 1930 and 1980, however, about 100 million elm trees died from a fungus called Dutch elm disease. Happily, the tree has made a comeback as of the late 1990s. Elms like moist areas, and will follow rivers to grow where many other trees will not. As with other allergenic plants, the elm produces flowers and fruit, which release pollen into the air.

Elm facts:

Appearance: Elms have a characteristic vase shape. The trunk splits on the top into large branches, and the smaller offshoot branches give the elm a "weeping" shape. Elm leaves are pointed with jagged edges.
Peak time: Elms flower in the early spring. The flat fruit ripens and falls in late spring to release a seed.
Location: You'll find elms all over the eastern and midwestern United States.

4: Mulberry

Mulberry trees were imported to the United States from China as part of an attempt to establish the silkworm industry. Mulberries are a silkworm's natural food source. Mulberries produce flowers and fruit, and the flower's pollen is wind-borne and highly allergenic. Mulberry trees are also popular ornamental trees, and you'll often see them planted along a street. And mulberries are edible, of course.

Mulberry tree facts:

Appearance: The mulberry tree ranges in size from 20 to 60 feet tall. It has shiny, lobed leaves. Its fruit is about an inch or so long, and is pink to dark red in color.
Peak time: Mulberry trees peak from winter to summer, but it flowers in the spring. Blooms are small, greenish-yellow, and spiky.
Location: You'll find mulberry trees in woods and river valleys in the eastern and western United States.

3: Pecan

The pecan tree is a type of hickory tree. It's also one of the most allergenic trees out there; it can be as allergenic as ragweed. The tree is native to North America, and is highly prized for both its timber and nuts. In fact, pecan trees in the southern United States produce more than 250 million pounds of pecans in a single year. Oil from pecan nuts is used in everything from processed foods to cosmetics and soaps. Its pollen grains don't travel far but are very large -- therefore, they're also very allergenic.

Pecan tree facts:

Appearance: A pecan tree can grow up to 200 feet tall, but when it's cultivated it's typically much smaller. Its leaves are compound -- with leaflets -- and can be up to a foot long. Its nuts are inside husks that split open once they're mature. They're about 1.5 to 2 inches long.
Peak time: Spring is the peak time for pecan trees.
Location: You'll see lots of pecan trees in Georgia and Texas, as well as the rest of the southeastern United States, and in Indiana and Ohio.

2: Pigweed

The pigweed is a family of weeds. There are more than 500 species of pigweed, including common pigweed and tumbleweed. It's an aggressive weed that reproduces by seed, and you'll see it in landscapes, on roadsides, and in pastures, among other places.

Pigweed facts:

Pigweed can grow up to 6 feet tall. It has bristly green flowers clustered along the sides and top. The common redroot pigweed has a reddish color at the taproot.
Peak time: Pigweed blooms and releases its pollen from spring all the way to fall.
Location: You'll find a lot of species of pigweed in the northern and western United States.

1: Oak

It's important to remember that it's not the plants with big showy flowers that cause your allergies to flare up. Plants with large grains of pollen, like flowers, are insect-pollinated. Plants that rely on airborne pollination, like oak trees, have small grains of pollen that will aggravate allergies. Oaks bear fruit -- acorns -- that take up to a year and a half to mature. Oaks are highly prized for their lumber.

Oak tree facts:

Appearance: Oak trees are large, rounded trees. There are more than 600 species of oak trees in the world, and they come in all sizes. An oak tree has green (sometimes bluish) leaves with rounded lobes. The flowers are called catkins, and those are what release the vast amounts of pollen.
Peak time:Oaks flower in the spring.
Location: You'll often see oak trees in the woods. Oaks are common in the Atlantic coastal plain, from Texas to Virginia, as well as Florida.