Spacing in raised beds is different from that in row gardens. Basically, row gardens have more room to go around than raised beds do, so they can give all that room to each plant, and the gardener can walk up to each plant and examine it carefully.
OTOH, in a raised bed, the gardener can reach in from any side/end and tend to any given plant. Therefore, he/she need not be able to walk
to each plant (one of the reasons for the row-garden spacings). Thus the recommended spacings for raised-bed plants are based on the mature sizes of the plants.
How big will X plant be when mature? ==> Then plant the seeds/transplants that far apart. Example:
If you're planting beets (a good possibility this time of year, at least in the Northern Hemisphere) which are 3" in diameter when mature, plant the seeds at least 3" if not 4" apart to give the beets enough room to develop. Be ready to thin them down to this spacing, too, when the seeds send up multiple seedlings. Beet seeds (and chard, same plant, just bred for root vs. leaf development) are little seed clusters. If you can look at one under a magnifying glass, you'll see their potential for sending up so many "plantlings."
Another principle is interplanting. It's not necessary to plant all the (say) beets together here
and all the kale together there
; they can be planted among each other. This is more important in hot weather, when plants that want slightly less heat can be planted in the shade of those that want slightly more heat.
For good diagrams of how this works, see Jon Jeavons' [url=https://www.bountifulgardens.org/prodinfo.asp?number=BEA-0301]How to Grow More Vegetables....
[/url]. He uses triangular or hexagonal spacing for seed placement rather than lines/squares. (The link I've provided is to Jeavons' own organization.)
Mel Bartholomew (Square Foot Gardening
) has yet another system. I used his system quite conscientiously when I returned to gardening in 2008 after a long hiatus (car accident), but got more return for my efforts with Jeavons' approach.
Sunset Zone 17, USDA Zone 9