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Over the past several weeks, local gardeners have been busily turning soil, planting seeds and transplanting what they hope will thrive in the short celebration that is summer in Juneau.

Whether you prefer to grow flowers or vegetables, a grassed lawn or a landscaped yard, it's difficult to resist the lure of nurturing at least a few new plants or caring for the existing greenery around your home. If you rent, you can still enjoy container gardening, help a friend who likes to work in their yard, or look into getting a plot at the community garden.

Whatever kind of gardening or yard care you do, weeds seem to be a constant. Even early on, as you anxiously wait for seeds to sprout or transplants to gain some momentum, weeds seem to consistently outpace the intensional plantings. It can be frustrating trying to keep them in control, and rest assured the battle will continue until the days become too cool and short to keep fighting.

Some plants that are often considered weeds are in fact native plants. Horsetails and fireweed are two weedy plants that will spread quickly and tend to outgrow cultivated plants easily. While ubiquitous and potentially undesirable, they are nonetheless in their natural environment and are relatively easy to keep under control. Some common nonnative weeds that plague us locally include dandelions, pineapple weed, chickweed, plantain, and buttercup. These plants are easily recognizable as most everyone who owns or cares for a yard or garden has them. They are so common that they're sometimes not included on invasive weeds lists-almost as though their presence is generally accepted as an inevitable by-product of civilization.

Care should be taken, however, with nonnative invasive species that pose serious threats to the ecology of our area. Some of them are attractive and may be sought after by the untrained eye, or inadvertently shared with others as easy-to-grow ornamentals. Examples include orange hawkweed (featured in the May 9 Not in My Backyard article), ribbon grass (also known as ornamental reed canarygrass), oxeye daisy, bishops weed and ornamental jewelweed.

Another invasive weed that is commonly ignored in our area is sweetrocket or dames rocket. It resembles a native fireweed species but does not have clefted flower petals. I have often heard people refer to it as phlox, as its pretty white or lavender flowers resemble the popular garden flower. However, phlox actually has five petals and does not have the same invasive characteristics as sweetrocket.

Why worry about weeds? Other than being a nuisiance when too much of them grow in your own yard, what harm can a pretty flower do? Invasive weeds can crowd out native plants as they usually win the competition for soil nutrients and may resist colonization by other plants. Some species, such as garlic mustard, are capable of altering the soil microbiology so that other plants cannot become established. The result is a decrease in vegetative diversity, which can have negative impacts on native plant and wildlife habitat. Once invasive species become established, it can be difficult to eradicate or control them. They may reproduce rhizomotously such as bohemian knotweed - and therefore are nearly impossible to eradicate - or their seeds may be plentiful and viable for years to come, requiring repeated treatment.

You can get more information about weeds at the Alaska Committee for Noxious and Invasive Plants Management website (http://www.uaf.edu/ces/cnipm/index.html) or by contacting Cooperative Extension Service. Learning about what grows in your yard will not only help guide your gardening efforts, but may prevent spreading problem invasives to your neighbor or to the wild.

• Not in My Backyard is a monthly feature about invasive species created by U.S. Forest Service botanist Ellen Anderson. Samia Savell works for the U.S.D.A. Natural Resources Conservation Service, and can be reached at samia.savell@ak.usda.gov

An invasive species is one that is not native to an ecosystem, and is likely to cause harm to human health, the economy, or the environment. This column will address plant and nonplant invasives. Contributors to this column will include Juneau Invasive Plants Action members, the Juneau Watershed Partnership, U.S. Forest Service State and Private Forestry, and the National Marine Fisheries Service. Others may be added in future columns.