I bought a gallon of Round-up, sprayed it, waited for two days but no result. There were some vaguely yellow leaves, but most of the groundcover was lush green, just like before. I decided it's time for more drastic measures. Took out my 8HP lawnmower and three hours + a dull blade later I had only mowed 200 of 600 square feet. Now I ended up with 200 square feet of thick brown roots, and they are so tough that I lost any hope of getting them out. Plus, I have some rhododendrons and trees in the area, and cannot use any brute-force mechanical devices.

Time to raise the white flag. I gave up!

I'll deal with the invasiveness by cutting as appropriate, but now I need to repopulate the damaged area. Is vinca quick at restoring itself, or do I need to put even more effort into getting it back to where it was when I started? Does it like the same fertilizer as the rhododendrons?

Thanks!

You'd probably have to use a scrub-killer to make any difference - and herbicides of that strength tend to linger in the soil.

You might want to experiment with the following: pick a patch you'd love to remove and dump your grass clippings over. No more than a square yard and clippings about six inches thick. Leave it to heat up. After a month the ground is likely to be damp, the Vinca not so pleased with itself, and much easier to either fork out or (eek!) take out using a pick axe that has a narrow blade at one end. It's much easier to use for getting into difficult places than a mattock or spade.

Under the rhododendrons you can use a good thick layer of untreated sawdust. If it has been composted using horse manure or steer - all the better. What you're wanting to do is change the soil texture and persuade the Vinca to bring its roots into that more friable blend.

Deepest sympathy for the sheer amount you have to cope with. If you have a neighbour who harbours the stuff make your first clearance along the boundary to create a buffer zone you can keep clear.

If it's 'all yours' pick just one patch to really clear before you move on. It's slow and decidedly unglamourous - but it makes a lasting difference. And, if you do your daily garden prowl with your faithful fork or pickaxe in hand - any stragglers can be instantly removed and consigned to the drying heap.

If your climate will let you - don't stop for winter. It's worth all the frozen muddy fingers to see a greatly diminished patch of little blue flowers come spring!

Thanks for the great ideas and for sympathizing with me during this difficult time :)