Dandelion lawn

If he rotavates he will break the long roots which will all produce new ones! Dandelions have such long roots and all of it needs to come up. Think I might use weed killer.

He could use an Autumn weed 'n' feed, which might reduce the numbers. I have Green Thumb in twice a year (spring and autumn) to do mine as the stuff they use seems to be more effective than what you can buy yourself, and I have very few weeds appear in my lawn.

I stab mine “down the root” with a long screwdriver or skewer dipped in Jeyes fluid - in essence I “inject” the weed root with disinfectant. Guaranteed to kill the dandelion and only the dandelion in a few days.

I use a lawn weedkiller. Works within a few days, and the grass grows to fill the space.

Lawn weedkiller is what I use and it's very effective.

Thanks for the advice. I'll tell my son grans recommend lawn weedkiller and why not to rotivate.

My son has bought a sack of lawn weedkiller granules. It is a large area of dandelion and I hope he kills them in time to grow grass on the area before the end of the growing season.

Me, I like dandelions and would keep them but grass is nice too, and my son's taste is more conventional than mine.

I prefer using granular products too just because messing around with sprinklers is not for me, I don't want any poison on my skin. The best solution here is to use weed preventer as this article advises and only after that start planting. If that's not possible that I would go with organic means instead.

Weeds in a lawn are easy to kill using granules but you do need a proper applicator, I do like the screwdriver and Jeysfluid idea - a proper applicator.
Coarse grass is different, if frequent mowing does not produce the result you want, rotavate and returf is the best answer but it is expensive. Even then it needs to be maintained because weeds will invade over the years.