[colleensj]

I know radishes don't take long to grow and I sowed mine around the 10th July.

They're about 3/4 inches tall atm....do you think they're about ready??
I only have a few so I dont wanna pick one unless they're ready.....

any tips? 

[Sue33]

sooner rather than later, they go woody really quickly, can you see them at all??
you should be able to see their tops, i would pull one, you can always plant some more now, for harvesting in a few weeks

[Lewjam]

yea, also this time of year they bolt at any hint of hot weather lol

I keep planting them and i just keep getting flowers heh.

You should also be able to see if there ready by the amount of red you can seeabove the soil.

They oftern lift them selves slightly -if you plany plenty just pull on and find out heh.

[DD.]

To back up what others have said, you should be able to see what you're pulling up and they do go to seed very quickly at this time of year, often without making a radish.

I don't bother with them after May as they usually end up straight in the compost bin.