You could use str.count with space ' ' as delimiter.
In [1716]: count = df['fruits'].str.count(' ').add(1).value_counts(sort=False)
In [1717]: count.index = count.index.astype('str') + ' words:'
In [1718]: count
Out[1718]:
1 words: 2
2 words: 2
3 words: 1
4 words: 1
Name: fruits, dtype: int64
Timings
str.count is marginally faster
Small
In [1724]: df.shape
Out[1724]: (6, 1)
In [1725]: %timeit df['fruits'].str.count(' ').add(1).value_counts(sort=False)
1000 loops, best of 3: 649 µs per loop
In [1726]: %timeit df['fruits'].str.split().apply(len).value_counts()
1000 loops, best of 3: 840 µs per loop
Medium
In [1728]: df.shape
Out[1728]: (6000, 1)
In [1729]: %timeit df['fruits'].str.count(' ').add(1).value_counts(sort=False)
100 loops, best of 3: 6.58 ms per loop
In [1730]: %timeit df['fruits'].str.split().apply(len).value_counts()
100 loops, best of 3: 6.99 ms per loop
Large
In [1732]: df.shape
Out[1732]: (60000, 1)
In [1733]: %timeit df['fruits'].str.count(' ').add(1).value_counts(sort=False)
1 loop, best of 3: 57.6 ms per loop
In [1734]: %timeit df['fruits'].str.split().apply(len).value_counts()
1 loop, best of 3: 73.8 ms per loop
