The simplest definition of a weed is any plant growing where it's not wanted.

But for years in gardening, that usually has included any wild plant growing alongside the cultivated varieties from the garden center. This meant that most wild plants were considered weeds no matter how pretty they might have looked in the garden.

That's changing.

"There is a big push to have the gardening public use more natives in their gardens because of their natural adaptation to our climate and particularly their support of native insect populations," said Brian Maynard, a University of Rhode Island professor of plant sciences and the treasurer of the Rhode Island Wild Plant Society (RIWPS).

In honor of National Weed Day, which is celebrated on March 28, and the start of the gardening season, The Providence Journal asked RIWPS for some of the "weeds" that are deserving of a place in the garden.

7 native plants to grow in your garden

Here's the list:

• Common Milkweed,Asclepia syriaca: This flowering plant blooms in a sphere of pink flowers in the summer, but what it's best known for is being the host plant for Monarch butterflies. It does have a competitive root system, so consider that when you place it.
• Common Yarrow,Achillea millefolium: Often seen in vacant lots, this plant's flower heads consist of dainty florets that look just right in a wildflower bouquet. It has many color variations.
• Jewelweed,Impatiens capensis: With little orange, trumpet-shaped flowers, this annual often attracts hummingbirds.
• Switchgrass,Panicum virgatum: This tall roadside grass can make a dramatic statement in a garden.
• Little bluestem,Schizachyrium scoparium: Another roadside grass, as the name suggests this one has a blue color that makes it striking in a garden and is on the short side at 2 to 3 feet tall.
• Self heal, Prunella vulgaris: In the mint family, this plant is one of the few natives that grows around the world, and it has medicinal uses.
• Woolly blue violet,Viola sororia: The state flower of Rhode Island (and Illinois and New Jersey), this little flower blooms from April until June.

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Where to get native plants

If you don't have them already growing on your property, some of these plants can be found at nurseries, but others are trickier to track down.

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That said, the Rhode Island Wild Plant Society does have two plant sales a year. This year, the first will be May 15 from 9 a.m. to 2 p.m. at Casey Farm, 2325 Boston Neck Rd., North Kingstown. The second will be June 3, 9 a.m. to noon, at the URI Botanical Gardens, 105 Upper College Rd., South Kingstown.

There will be members-only pre-sales the hour before both events.