The following anonymous poem (“Spring is sprung, the grass is riz, I wonder where the flowers is”)  is sometimes called the Brooklyn (or Bronx) National Anthem. The poem has been cited in print since at least 1936.
 
Authorship is unknown. American poet Ogden Nash (1902-1971) is often credited, but the poem is not his.
 
“Spring has sprung, the grass has riz, I wish I were in the chocolate biz! Happy Easter!” is a variation from 2015.
 
     
Newspapers.com
13 September 1936, Pampa (TX) Daily News, pg. 12, col. 2:
The following “poems” were clipped from the Clarendon News:
 
An Ode to Spring.
Spring is came,
The gass is riz.
The grass is riz,
The flowers is.
 
Newspapers.com
21 March 1937, Pampa (TX) Daily News, pg. 1, col. 2:
‘Spring Has Came, Grass Has Riz, Don’t Know Where the Flowers Is’
This is the first day of spring—and the winter of 1937 is history, according to the man who figured out the official calendar.
   
Newspapers.com
21 March 1937, Ogden (UT) Standard-Examiner, “Junior High Students Will Hold Spring Dance On March 26,” pg. 11-A, col. 2:
SPRING IS HERE
Spring is here
The grass is ris,
I wonder where
The flowers is.
 
Newspapers.com
15 April 1937, Pauls Valley (OK) Democrat, pg. 2, col. 3:
SPRING CLEANING
“Spring has came, the grass has riz, I wonder where the birdies is?”
   
1 May 1937, Chicago (IL) Daily News, sec. 3, pg. 3, col. 2 photo caption:
“Spring has came, the grass is riz, I wonder where them flowers is?”—Lee Wal Kow’s philosophy of spring—and so spring comes to the Midway ...
 
9 April 1938, The Idaho Statesman (Boise, ID), “Collegians Snooze, Golf, During Spring Vacation” by Essamary Parker, pg. 5, col. 5:
Spring has come
The grass is riz
I wonder where
The flowers is?
 
Newspapers.com
7 August 1938, Charlotte (NC) Sunday Observer, “Squibbies,” Parade of Youth sec., pg. 6, col. 2:
SPRING SONG.
“Spring is here,
The grass is ris.
I wonder where
The flowers is.
     
Newspapers.com
22 March 1939, Ogden Standard-Examiner, “Sol’s Sunshine and Shadow,” pg. 4, col. 6:
Spring is spring,
The grass is riz,
I wonder where
The pozies is?
 
24 March 1940, Sunday News (New York, NY), pg. 15C, col. 2 ad:
O’ SPRING IS SPRUNG
THE GRASS IS RIS.
GOSH! I WONDER WHERE
THEM FLOWERS IS??
(Lawson-Hart Co.—ed.)
 
11 April 1941, Reno (NV) Evening Gazette, Sports Roundup by Eddie Brietz, pg. 21:
ODE TO SPRING.
Spring has sprung,
The grass has riz;
But it’s still unsung
Where the flowers is.
 
23 March 1942, Austin (TX) Statesman, “The Looking Glass,” pg. 10, col. 5:
Spring is sprung
The grass is riz.
Wonder where
The flowers iz.
 
4 March 1943, The Salt Lake Tribune (Salt Lake City, UT), “Senator From Sandpit” by Ham Park, pg. 6, col. 5:
Spring has sprung,
The grass has rizz,
I wonder where the
Birdies is?
(...)
—Preachin’ Sam,
Springville, Utah.
   
29 March 1944, Coe College Cosmos (Cedar Rapids, Iowa), pg. 2: 
Spring has sprung,
The grass is riz,
I wonder where
My blanket is.
(OK, so it’s old, but it’s pertinent.)
   
25 April 1944, Brainerd (MN) Daily Dispatch, pg. 5:
“Spring is here, the grass is ‘riz,’ I wonder where the flowers is—.”
   
19 March 1945, Maryville (MO) Daily Forum, pg. 2:
“Spring is sprung,
The grass is riz,
I wonder where the flowers is.”
 
9 April 1947, Charleston (WV) Daily Mail, pg. 6:
Spring is sprung;
The grass is riz.
I wonder where the flowers is?
 
20 March 1948, Washington (DC) Post, pg. B14:
Spring has spring,
The grass has riz.
I wonder where
The flowers is?
W. H. L.
554 S. 18th st.
Arlington, Va.
 
21 March 1948, New York (NY) Times, pg. SM18:
“Spring is sprung,
The grass is riz,
I wonder where the flowers is.
The boid is on the wing—
Absoid!
Of course the wing is on the boid.”
—Anon.
 
26 March 1948, Washington (DC) Post, pg. C8:
MAIL BAG
Dear Bill:
Down in North Carolina, your “Spring is sprung, grass is riz” poem has been a favorite for years. I don’t know the name of the author, but I object to seeing it published over somebody else’s initials.
Annabel Barnes
2131 I st. nw.
 
1 May 1952, The Christian Science Monitor, “Spring Ditty,” pg. 21, col. 5:
(Common Version)
Spring has sprung; the grass is riz.
I wonder where the birdies is.
 
(New England Version)
he birds is come; the grass is riz.
I wonder where the springtime is.
ALPHEUS HASKINS
   
Cassell’s Humorous Quotations
by Nigel Rees
New York, NY: Sterling Publishing, Inc.
2003
Pp. 89-90:
Der spring is sprung
Der grass is riz
I wonder where dem boidies is?
 
Der little boids is on der wing.
Ain’t dat absoid?
Der little wings is on der boid!
Anonymous (New York). “The Budding Bronx,” quoted in Arnold Silcock, Verse and Worse (1952).
     
8 May 1957, Los Angeles Times, Cityside with Gene Sherman, pg. 2:
VERSESIDE—Jose Bates has been having a little italic trouble with his garden:
 
Spring iz sprung
The grass iz riz;
I wonder where
The flowers iz?
 
18 January 1976, New York (NY) Times, “Talking Brooklyn in Joisey” by Mario Pei, pg. 328:
It was ultimately sublimated into exalted verse in what is described as “The Brooklyn National Anthem,” although its lack of nationalistic features makes it applicable to Hoboken and Jersey City as well:
 
“De spring is sprung,
De grass is riz;
I wunneh wear de flowers is.
De boid is on de wing—”
 
“Absoid! De wing is on de boid!”