What to fill raised plant beds with ?

[Jazz12]

Continuing with helping MIL do up her little garden, we have a few wooden raised plant beds. She wants to grow tomatoes and other veggies in them.
They look quite deep (abt 1.5ft). Do they have to be filled entirely with compost !??

I would buy a couple of bags of straw/hay and mix it with some non printed cardboard (like Amazon boxes) and food waste from the kitchen to fill it and then when it's planting time, turn it and add some normal garden centre compost on top. The bottom layer will break down over the summer.

We put hardcore and rubble left over from our garden works to part fill.

Pretty much anything! I use home made compost, old compost from failed seedlings and containers, any small branches and prunings, wood chippings, Everything goes in.

You don't necessarily have to fill them up to the top this first year. You can add grass clippings through the year, and should mulch as well in autumn, it will soon fill up.