DALLAS — Fashion retail may be in the doldrums, but indie boutique Planet Bardot is pushing ahead.

The shop for casual hip style on Knox Street nearly tripled in size last month to 2,800 square feet.

At the same time, owners Diana and Bob Tabesh modernized the facade of the entire block, which they bought last year, transforming it from ragtag to sleek with cast stone blocks and bigger windows. The strip abuts Apple, and its update meshes with the neighborhood’s recent metamorphosis into a hot spot for fashion specialty stores.

“Knox has a mix of restaurants, furniture, retail that Dallas doesn’t have anywhere else,” said Diana Tabesh.

The couple has already commissioned plans to expand the 6,000-square-foot building by extending it back and adding a second story by spring.

She opened the boutique three years ago after selling Denim for Immortality and Aristocrat Denim, which she founded and designed. Business took off fast, posting 20 percent annual gains. Bestsellers include Rag & Bone, Lemlem and Frame denim plus recent additions including Iro, Ulla Johnson, and Raquel Allegra. Men’s wear begins arriving in August, and additional categories and a beverage bar are on tap for spring when the second floor opens.

“I’m introducing men’s on a small scale in August, and then we’ll go big in the spring,” Tabesh explained, declining to project sales. “It will be on the first floor with cosmetics, fragrances, homeware, dishes, cool art stuff — things you don’t see everywhere. I’ll take the main floor [of women’s fashion] up.”

The addition will enlarge Planet Bardot to 7,000 square feet and the entire building to 15,000 square feet.

The impending departure of nearby Forty Five Ten for bigger digs downtown is part of her rationale for the expansion. Forty Five Ten was the first — and for many years the only — fashion tenant in the Knox Street area, which has long been dominated by home furnishings retailers including Crate & Barrel, Pottery Barn and Mecox.

With the effort of Sarofim Realty Advisors, which bought a lot of property in the area and rebranded it Knox District, the neighborhood is evolving into a key area for fashion retailers that prefer street-side locations. Typical rents on Knox Street have risen to $90 a square foot from about $55 a square foot in 2013, according to Tabesh. Among the new tenants are Sid Mashburn, Kate Spade, Lululemon and Steven Alan.

Knox Street is only eight blocks long, and it runs straight into Dallas’ wealthiest neighborhood — Highland Park. Nearby is rapidly growing Uptown, another of the city’s few walkable neighborhoods blending residences with offices, entertainment, merchants and services.

Sid Mashburn and Ann Mashburn opened in November on Knox Street next to the leafy Katy Trail, a popular destination for walkers and bicyclists. “There’s a lush romanticism about the whole neighborhood that is just fantastic,” said Sid Mashburn, noting he’s especially fond of the anachronistic soda fountain at Highland Park Pharmacy.

Trader Joe’s opened in March on Cole Avenue in Armstrong at Knox, a newly built mixed-use complex on land that formerly held an appliance store. One- and two-bedroom apartments there rent from $1,895 to $5,550, and retail tenants include Stag, a rustic contemporary men’s wear chain based in Austin, Sur La Table and a Japanese restaurant, all of which moved from one block away.

Redevelopment plans are on the drawing board for their previous locations plus a former Chili’s restaurant, which will be subdivided into four shops, according to Michael Nagy, senior vice president of CBRE UCR, which handles leasing for Sarofim Realty. He is focused on fashion.

“There is a lot of interest in being on Knox from brands all over the country,” Nagy said. “It’s just a matter of sorting out who works.”

Planet Bardot occupies three of the seven storefronts the couple owns. The other four leases expire in the spring, and Tabesh expects to rent at least two of them to complementary retailers, such as cosmetics, sunglasses, candles or shoes. The tenants are a postal center, a tailor and a popular local vendor of frozen custard.