I have a slope that was landscaped three springs ago. A large area, about 50' x 50', was planted with Vinca. The first two seasons, attacking dandelion and thistles that grew between the vinca was pretty easy. This year the vinca continued to spread and weed killing became more difficult. Our late summer was extremely dry and this compounded the problem. We have finally had some good soaking rains that have allowed me to pull weeds, but judging by some of the roots, I'm going to have some serious problems next growing season. As the vinca continue to spread and thicken, will they be able to choke out the weeds? or am I going to be left with a bed of thick vincas that are very difficult to weed because of the vinca density and the grade of the slope?

vinca major (or periwinkle because of the blue flowers) will prevail and become good ground cover. The beauty about vinca is you can just pull out a piece with a good root and dig a hole with your finger and stick it in and it will root and multiply.

But... it does require some work as always in a garden where you have perenials. You will eventually have a good bed of vinca without too much trouble, and it will prevail,just have patience.

I move mine around all the time and start it different places, mostly under pine trees where not very much will grow ordinarily.

Thanks tickle. I thought that was the reason for the landscaper to plant vinca, but I was becoming concerned, especially since the late summer weather allowed the dandelion to proliferate.

Dandelions in any ground cover are a pain. I have well established vinca, and I still fight a few of them. Careful spraying or digging will control them.

If danelions and Thistle is your main concern perhaps trying a preemergent weed control! These two particular weeds usually spread via seed! That will go for many other weeds in fact, not all though. Any preemergent weed control will not harm the growth of the vinca

Dandelions while spreading by seed are also a perennial, but the suggested preemerge like Preen will help. Get it down early spring

A good crop of Vinca will pretty much choke out weeds.

Spot spray the weeds with a 2-4 D such as Weed be Gone. It will not hurt the vinca. In fact I have tried to eradicate vinca with Round up to no avail