With St. Patrick’s Day only two weeks away, the city of Boston is preparing to host the biggest celebration of the holiday in all of Massachusetts – the South Boston St. Patrick’s Day parade.

Andris Nelsons is being forced out as music director of the Boston Symphony Orchestra in the summer of 2027 after 13 seasons.

The orchestra made an unusually blunt announcement Friday.

“The decision to not renew his contract was made by the BSO’s board of trustees because, beyond our shared desire to ensure our orchestra continues to perform at the highest levels, the BSO and Andris Nelsons were not aligned on future vision,” the BSO said in a statement from its trustees and CEO Chad Smith.

A five-time Grammy award winner, the 47-year-old Nelsons is currently leading the Vienna Philharmonic on a U.S. tour and was to conduct the orchestra in Naples, Florida, on Friday night.

“While this is not the decision I anticipated or wanted, I am unwaveringly committed to you and to our work together,” Nelson wrote in a letter to BSO musicians and staff that was released by his management agency. “I understand the decision was not related to artistic standards, performances, or achievements during my tenure, and, therefore, my focus is straightforward: to protect the music, support the orchestra’s stability, and continue to perform with the musicians of the BSO at the highest artistic level.”

Nelsons made his BSO debut in March 2011 at New York’s Carnegie Hall as a replacement for James Levine, who announced 10 days earlier he was stepping down as BSO music director at the end of the 2010-11 season because of poor health.

Nelson was announced as music director in May 2013 and given a five-year contract starting with the 2014-15 season. The orchestra announced contract extensions in 2015 and 2020, then in January 2024 said he was given an evergreen rolling contract. He was bestowed an added title of head of conducting at Tanglewood, the music and educational center that is the orchestra’s summer home.

The last extension was announced a few months after Smith, who had been with the Los Angeles Philharmonic, started as the BSO’s chief executive.

Nelsons was music director of the City of Birmingham Symphony Orchestra in Britain from 2008-09 and has been chief conductor of Leipzig Gewandhaus Orchestra in Germany since the 2017-18 season. He married soprano Kristine Opolais in 2011, and in 2018 they announced their divorce.

Boston will have the third vacancy among major U.S. orchestras. Gustavo Dudamel is leaving the Los Angeles Philharmonic this summer after 17 seasons to become music director of the New York Philharmonic and Franz Welser-Möst will depart the Cleveland Orchestra at the end of 2026-27 after 25 seasons.

In addition, Klaus Mäkelä takes over the Chicago Symphony Orchestra in 2027-28, when he also starts as chief conductor the Royal Concertgebouw Orchestra in the Netherlands.

But the story of the Poor Clares’ monastery — or as it’s known on the books of the Boston Planning Department, 920 Centre Street — is, at least for now, a case study on how housing doesn’t get built in this city.

It’s a story about how one midsized project with everything going for it — a world-class architect, a brilliant landscape designer, and a developer willing to make one compromise after another to the size and layout of the plan — still can’t move the needle in the face of one powerful opponent.

Well, make that one powerful opponent who has the ear of City Hall.

Faced with dwindling numbers in their order (they were down to 10 in 2022) and a Vatican mandate to consolidate, the sisters decided to sell their 2.8-acre parcel and the aging monastery building to developer John Holland. The building, which they had occupied since 1934, was expensive to heat and in need of extensive repairs.

They relocated to Westwood in 2023, hoping to expand those quarters to accommodate another 10 nuns from around the country as soon as the sale of the Jamaica Plain property became final, contingent on the approval of its redevelopment.

They’re still waiting.

The former monastery is neighbor to the Arnold Arboretum, land owned by the city but under a renewable 1,000-year lease to Harvard University. And no question, the 281-acre parcel is a tree-filled treasure for researchers and picnickers alike. Just try getting near the place on Lilac Sunday.

But the Arboretum, or rather its director, William Friedman, a Harvard evolutionary biology professor, has emerged as a powerful foe.

“The development has been part of the city’s planning process for nearly five years and has undergone several revisions,” Sr. Mary Veronica McGuff, the order’s abbess, wrote in a letter to Mayor Michelle Wu in January and shared with the editorial board. “We are very disappointed to learn that the main obstacle is … the Arnold Arboretum.”

She revealed that the order had earlier offered to sell the property to the Arboretum, but was rebuffed.

“It’s upsetting that our progress is now being hindered by an institution that declined the opportunity to take stewardship of the land and is now making unreasonable demands for its redevelopment,” she said in the letter.

In fact, its market rate condo component, once slated to be five stories high, has been reduced to four stories. Those 38 senior rental units planned for the monastery building will include 25 affordable units.

Project architect David Hacin, winner of the Boston Preservation Alliance’s 2022 President’s Award for Excellence, is equally bewildered.

“I don’t understand how a project that is so good on so many levels is being held up for years, literally, over asks that seem, to me, completely unreasonable,” Hacin told Globe business reporter Catherine Carlock. “If we can’t build five-story buildings, how are we going to solve the housing crisis?”

How indeed.

The developers have done shadow studies, a sunlight analysis, and tree root studies to convince Arboretum officials that the planned housing would do no damage to the magnolia tree roots on the perimeter of Harvard’s grounds, which seem to be their main bone of contention.

The project’s landscape architect Mikyoung Kim has surely not acquired her international reputation for “ecological restoration” by murdering magnolia trees.

Friedman has met with Boston’s planning chief, Kairos Shen, but as of Thursday the sisters have not yet been granted a similar opportunity. Nor have they heard from either Wu or Shen (who was copied in on the Jan. 12 letter) since they made their appeal for help “in finding a solution that allows this project to move forward and for our community to finally settle into our new home.”

In a statement to the Globe editorial board, Wu said, “Large properties like 920 Centre Street are significant housing sites for Boston, and we are working actively with all parties to advance a plan that would deliver homes our city needs.”

For the past year, experts have been warning that the slumping number of building permits in Greater Boston — down 44 percent last year from four years ago — do not bode well for an increase in the future housing supply. That dearth in supply is driving up prices and rents.

And while the Wu administration is quick to blame President Trump’s tariffs and rising costs for the construction slump, it fails to look in the mirror. Enabling the kind of Not In My Back Yard obstructionism that is keeping a good project on the drawing boards for years will never get Boston the kind of housing it needs to keep pace with demand and allow this city to thrive.

Editorials represent the views of the Boston Globe Editorial Board. Follow us @GlobeOpinion.