Plant now and later for ongoing crop. Some are good for greens and some for the root. All must be thined, so the beetroot has room to grow. Enjoy the green thinings. The smaller the more tender.
Even is you plant late as long as they sprout you have grees and maybe some baby beets.
Beets have 3 embroys in each seed, which is why you end up with so many plants and wondering why when you were so careful not to over plant.
Chard is of the same family so this is the time to plant this wonderful green.