Cutting rooted, what now?

[Kopparbergkate]

30 years ago (when he was but a wee lad) dh planted an apple pip and over the years it's grown into a mahusive tree with surprisingly nice tasting apples. Anyway, when fil died and we had to sell the house, we took a "cutting" (aka a random twig!) lobbed it into a glass of water, put it in the window sill and promptly forgot about it.

Fast forward a few months and roots have appeared and a little green bud - what do I do now? Can I plant it straight into soil or is there some interim next step??

Dh is away so I have sole responsibility for this and, as you can see from the massive preamble, it's a pretty big deal! Help!

Hi, as this has rooted in water, the roots will be very brittle, so as it is precious, treat it with extreme care!
Estimate the diameter of the roots and find a pot a couple of cm wider than that. Fill the pot with good potting compost (garden centre) and firm it down. The compost should be a good 4/5cm below the top of the pot. Really gently, place the cutting on the surface of the compost. Whilst holding it in place, gently fill the pot with more good compost. You may need more than 2 hands for this, and it is best if they are adult hands . Do not firm the compost as this will break the roots.
Water well, and as it has done well on your window sill, put it back there and wait. I personally would keep it indoors in an ever-larger series of pots for a year, then plant it out in the garden next April/May.
As the original tree was mahoosive, I hope you have a large garden, as the tree that will result from the cutting will be equally large. Pruning won't help - it will just make the tree larger. Of course, you could always just take a cutting and chop it down when it gets too big

Thank you! simple, step by step instructions exactly what I needed! Will try and round up some extra "adult hands" over the weekend

Currently house hunting so will make sure large garden is on the requirements list!