Roots growing under vinyl floor

[HiccupHaddockHorrendous]

I'm about to have a new vinyl floor fitted in my kitchen and when we pulled up the old vinyl there is a patch of tiny roots growing in one area of the room (only pulled up a small amount so far so there could be more!!).
Any suggestions of where to get advice on how to either treat it or which professional I need to get in?

What growing outside? Trees, ivy or possibly Japanese Knotweed. These could all come up through foundations.

However, dry rot produces a fern like stem pattern, it could possibly be that caused by damp in the floor timbers.

Sorry to alarm you.

dry rot looks a lot like roots.

You could have something growing in a mortar course and the roots coming through to the inside. That is likely to mean there is penetrating damp. Often the easiest to fix though.

Thanks for the replies!
They appear to be growing on top of the concrete floor.
Off to google dry rot!
The whole house is a damp mess a needs major work (rented) but will just be patched up for the foreseeable.

I think it's wet rot.

Wet rot shows as crumbly woodwork and is often a precursor to dry rot. If the property is rented then the landlord needs to be informed! It could be elsewhere and you could fall through the floor!

Yep, all the ground floor, wooden, skirting boards have crumbled and been replaced with plastic ones, over the last few years.
Landlady knows there are problems but is very reluctant to carry out any major work to fix it.
She's an elderly relative and the thought of disruption and cost terrifies her.
The terrace of three houses all suffer from terrible damp. Neighbours had a major refurb last year and the whole house had to be gutted. In one of their downstairs rooms, there were flagstones laid directly on earth. No foundations.
They had to move out for 4 months while it was being done and they're only small, 2 bed cottages.
The floors on my ground floor are all concrete so hopefully we won't fall through that
I completely accept that the house needs serious attention but will have to bide my time with getting landlady's permission.
There was water coming in through the disused chimney in the kitchen (haven't done enough research to know if that could be the cause of wet rot). This has been partially fixed (waiting for the builder to come back and replace the roof!!) so hopefully, things might improve.
I'm going to do lots of research this weekend and look for the best way to proceed.