How to obtain seeds from an already harvested daikon radish?

Question

I have in my kitchen a daikon radish of about fifty centimeters whose tops, shortened to 1 cm at the time of purchase, start to grow again even though it is no longer in the ground. They are today 8 cm long and look vigorous.

Do you think it's possible to make it go to seed before the root is completely depleted, and if so, how?

I'm considering putting it back in the ground or in a mix of sand and potting soil, after perhaps one night in the water, but maybe there is a better way.

The goal is to get seeds from this particular specimen (several species of daikon radish exist and obviously the supermaket is unable to say which it is), but also to succeed in the replanting experiment.

Note: I am in a temperate climate where there is no risk of frost until mid-December.

Answer 1

My preference would be in soil as you have planned and keep the soil moist. The idea is to keep the root and stem that remains hydrated to give the seeding process as much chance to complete as possible before the plant dies. Keep in mind that the flowering and seeding process in radishes, like lettuce and other multi-flowering plants, produces flowers and seed over a period of several weeks in the wild, with early flowers opening followed by later flowers to ride out any irregularities in the weather. Once you note that some of the flowers are setting seed decide on how many more flowers to permit to expand. The more flowers the more the load on the reserves of the root and the more quickly it will complete its life cycle.

Radish flowers in general are not self-pollinating; they need a pollen donor so the root will need to be out where pollen-carrying insects can get to the flowers. An alternative would be to manually pollinate using a fine brush or feather.

Answer 2

I would grow it in just water with nutrients, changed regularly. I suspect there is a high chance of the root going mouldy otherwise.