“Today I put the radishes, carrots, cauliflower, and cucumber in the planter. They are getting so leggy that they’re staying to lay down. Was this too soon, or too late. How tall should the sprouts be to transplant?”
HEAT is only going to be your friend for the Cucumbers. Carrots, Radishes and Cauliflower like it sunny and cool - so winter plantings for your zone.
Either look on line, or get yourself a book that is specific to your Planting Zone and you’ll get all the info you need on what to plant, when. You can only fool Mother Nature so far. ;)
Examples of what you’re looking for:
https://www.amazon.com/Florida-Fruit-Vegetable-Gardening-Harvest/dp/1591869056
https://www.amazon.com/Month-Month-Gardening-Florida-MacCubbin/dp/1888608242
I would leave the cucumber (just ONE plant) in your pot, but throw a tomato cage over it for support, or rig up something - cukes vine and will want to be trellised up. This also keeps them cleaner than if they trail on the ground.
Good luck! :)
Thank you Diana =o)