Me again with another question regarding my new allotment (many more
questions to follow, no doubt).

Looking north, my allotment is 34 feet long x 19 feet wide. My plan is to
construct raised beds of various sizes.

Potatoes, Corn, Lettuce, and miscellaneous other veggies will have their own
separate beds.

There will also be three main beds, running N-S, each 15 feet long x 5 feet
wide with a 2 foot pathway between each bed (totalling 19 feet wide).

These three main beds will have (1) Roots/Onions, (2) Legumes, and (3)
Brassicas.

Okay, the question is regarding the Roots/Onions bed -- Red and White
Onions; Leeks; Early and Late Carrots; and Parsnips.

Question -- is it better to grow one 15 foot row of onions, and one 15 foot
row of leeks, and one 15 foot row of carrots, and one 15 foot row of
parsnips, rows running north to south the full length of the 15 foot bed?
Or, should I treat the bed as 3 separate blocks (each 5'x5') and grow three
5 foot rows of onions, and three 5 foot rows of carrots, etc., (each 5x5
block would therefore contain just onions/leeks, just carrots, and just
parsnips - do you know what I'm trying to get at).

Sorry to be so clueless, but this is my first allotment and first attempt at
growing veggies.