If you planted too thickly, you can often replant the seedlings, but root crops don't do so well, except the onion family. Look for spacing recomendations for wide beds in Square Foot Gardening.

Its not a number of seeds that you should be concerned with. Its the space allowed per plant. So sure you can fit 30 carrots in a square foot but they wont grow to full size. And you can plant the correct number (16) but if two are growing too close together they wont grow straight or at all. So yes, it will be necessary to thin. Only certain plants transplant well. Radishes carrots spinach and cucurbits do not. Also carrots have been the last thing to germinate for me. Just keep them moist. Sometimes ill let two lettuces or spinach grow together because i usually harvest them young anyway so not as much concern about nutrient competition. Ill admit i just scattered my carrot and scallions seed in one bed because i was being lazy but i fully intend to properly thin them, even if i have to do it a little at a time.

Carrots are always an issue for people, because the seed is so small and light. I do large beds and sprinkle the seed from about 5 feet high, and it seems to need much less thinning than trying to plant in rows.

Just one small point - Mindyw3 says curcurbits don't transplant well. In my climate it would be high summer before the outdoor soil temp is high enough to germinate a squash seed. So it is standard practice here to grow cucurbits in modules indoors and transplant them. There is never any problem with them. I totally agree, though, on the roots and spinach.

Ive transplanted squash from the nursery no problem but id think digging them from the ground to move would be a bit harder.

Carrots can be tricky because they take so long to germinate (about 3 wks), and if you let the soil/seed dry out even once during that time, they die.

But there are some tricks...

Soak the bed well the day before you intend to plant and let it drain. Sow your seeds and get them covered with soil (about 1/2") and gently firm down.

THEN cover the bed with cardboard or plywood. Leave it there until they start sprouting. Start peeking after one week, then every day or two. Look closely -- they can be hard to see. When they start sprouting, remove the cardboard or plywood completely. You'll still have to keep them moist, but it isn't as crucial as when they're germinating.

If you're raking the seed in, you can overseed, because some of them will be covered too much and not be able to make it to the surface, some of them will be right near the surface and die when they dry out, but some will be just right.

Sue

Thank you all so much for your help. I think I planted way too thick and most of it is stuff that will not transplant well, carrots, beets, spinach, turnips, lettuce, radishes.

I looked everywhere to find a chart like the one for rows that says for 100' use ____ oz seeds. But I guess wide row planting is not as common. So I will learn and keep better records this year so next year I wont have to murder innocent seedlings!
I really didnt expect such great germination after last year.

Just follow the spacing on the seed packets or space a bit more than squarefoot guidelines and you should be ok.

Eliot Coleman goes into some detail about seed spacing in Four Season Harvest. The goal is to have minimal soil showing when the plant is at full maturity. If you know the recommended spacing for a single row, calculate how many rows to plant by fitting that in to the width of your bed; in other words, if your bed is 36" and your spacing is 10", you can fit 3 rows in. The outer rows should be at 1/2 the spacing distance, so in this case 5" from the edge of the bed. The middle row should be staggered in relation to the other two - your first 5 seeds will resemble the "5" side of a playing die. For baby greens, you would want 3" spacing, so you would get 11 rows, with the outer rows starting 1 1/2" from the edge of the bed. The assumption with intensive spacing, which is what Square Foot Gardening and wide bed planting are based on, is that you have created an optimal growing condition for the crop, so you can squeeze more in without risking having too little fertility or water. If you think your soil in the beds will need a few more years of improvement, you will get better results with wider spacing... and a bit more weeding.

luvncannin - you can transplant lettuces thinnings. Try to choose a cool overcast day. Water the plants first then dig out a clump of seedlings. Tease them apart with your fingers and replant where you want them. Water again. They will have a little growth check but that is all to the good because you don't want all your lettuce ready at once.
And remember you can snip off the excess seedlings of many vegetables and eat them in a mixed baby leaf salad.

Oh what great advice. I love this forum and if it werent for my garden I would lose days reading.
I belive the wonderful rain/hail took care of some of my thinning. no sarcasm we are so happy to have moisture we will take it any which way. I will simply replant several blocks a little thinner this time, and see what happens.
I am going to take notes from here and square foot gardening and get busy. This time I think I will put up a little tarp to keep the hail/downpour off of my seedlings.
Thank you all!!!