Posted: 14/05/2017 at 15:47
There are 3 main ways forward I think and they depend on patience and budget.
Th first is to get someone to dig out the stumps. Tree surgeons often have root grinders which will do this easily enough.
The second is to build raised beds using railway sleepers or bricks or recycled scaffolding boards or similar. They'd need to be about a foot deep to be effective or you could make them to knee height and have built in seating. You'd then need to fill them with a mix of garden compost, loam based compost and, if possible, some well rotted manure and then you can grow ornamental plants or maybe some shrubs or even edibles.
The third is to wait a year or two. The roots and trunks of pine rot fairly quickly and then you can dig it over and make a new bed enriched with garden compost.