I'd be inclined to put down cardboard or several layers of damp newspaper, followed by 2-3" of mulch and then plant the vinca through that by cutting an X and sinking the vinca into the soil, based on my experience with vinca. Mine roots a bit too well through anything - mulch over cardboard, lawn, other plants. By the time the vinca is wanting to root, it won't have any problem rooting well into and through the mulch. Light-based weeds will have a tough time growing up through the mulch and cardboard, but many won't be discouraged by only an inch of mulch IME.

i would go deeper with the mulch ... and forget the preen

it will take a year or two for the vinca to get going ...

and it is just as likely to go under/through.. as rooting from the top ...

and preen has a rather short active life span anyway ...

my gut tells me spend extra on mulch.. and save the money on preen.. its not a panacea ...

watering young transplants on a hill.. is going to be very important.. and rather hard .... and that is where i suspect your major issue will be ...

ken

LOL freiki !! I have to agree with you there. It's so very hardy. I have areas of my yard that it grows wild but it creeps up into other areas. I swear I've grabbed ahold of one 'vine' and started pulling it out of the ground and it can end up being 6 ft long...!!! So it's a tough cooking, thriving most anywhere.

And I agree with nhbabs' method. Tho I've never tried the newspaper method, I know it works (from others who have) and agree that by the time the vinca wants to root, the newpaper will have deterioated. And it shouldn't have a problem growing down thru even deep mulch.

And Ken's right about watering the new transplants.

It will take years for Vinca to grow so thickly that it covers the ground well enough to suppress other weeds, if ever. The nodes are quite far apart. Don't know what you plan to use for mulch, but Vinca is quite comfortable, vigorous, easily spreading around in several inches of oak leaves (which DO suppress weeds.)

anywhere I start a new flower bed, I cover the grass with a thick layer of newspapers,cut through the paper to plant the perennials, and cover with a mulch of bark. Works great though occasionally a few sprigs of grass will creep through, but easily pulled. newspaper disappears, but helps hold moisture for a time.

I had a beautiful patch of vinca grown over a number of years. Last year, it all disappeared after winter. Replanted in spring and this year, once again, it died. Any idea what kills vinca?

Too cold there?

I pulled it all up from my Mom's yard, I kill Vinca, but I haven't been to your house.

Growlove, that's how I always start a new bed! If you wait until the grass is definitely dead to pierce the smother, you'll have less grass in the planting holes, if that's why it's there. It's hard to wait, isn't it? Could just be from seeds dropped there already, previous years or earlier that year. Mowing with the chute facing away from beds helps too, as well as a border, like bricks, landscape timbers, something easy to trim against or drive mower tires along. If no new seeds are dropped and it can't creep in from lawn, grass won't reappear in beds, except the very occasional sprout. Pull as soon as you see it the first time, while easy to do.

I am thinking of trying to replace grass/weeds on a steep slope with vinca as well, so this is a helpful thread! The issue for me is that my slope is so steep, I don't think I will be able to mulch over newspaper or cardboard without it sliding right off. Can this method be used without mulch? Or could I stake cardboard onto the slope and then stake fabric or plastic over it instead of mulch?

biondanonima, I'd use a thick layer of a highly textured shredded mulch that will knit together well without the cardboard under it. You will want to be sure that the grass and weeds are killed first either via solarization if it's in the sun or with an herbicide such as Glyphosate/generic Roundup. Plastic and fabric interfere with movement of water and air, so things won't grow well. Without a covering both break down in sunlight, so you will then have shredded fabric and weeds rooting through it. Weed fabric doesn't generally work well anyway.

Here's my steep slope with mulch. It's a few years after planting after renewing the mulch in early spring before the plants sprouted. My first mulch was free chips from the guys trimming the wires along my road. I just stopped and asked if they would dump them at my house. Now my DH, a bowl turner, generates mulch for me. While the mulch did migrate down toward the bottom of the slope just a bit, it didn't move much and did a good job keeping new weeds from sprouting. I don't think I weed for an hour on this sunny slope over the course of a year. For me Vinca grows densely enough elsewhere in the yard that it's quite weed resistant, and it roots just fine into the mulch.

NHBabs - Thank you for the photo. That's wood chips from your DH? I so need to find mulch that will knit together like that. I Googled highly textured shredded mulch. No help. Photos seem the same as BigBox mulch that I scoop up from the bottom of the slope. Saw straw mulch and pine needle mulch, would they work?

I have in the past gone and checked the different bark mulches to find one with the right texture, and in some parts of the country you can find what is referred to as gorilla hair mulch which is very shreddy and will bind together well. Pine needle mulch would stay put better than straw I would think since I think the forked needle bundles would help it knit together. But my initial mulch while the perennials were just tiny starts was literally just the chips from the line crew clearing lines along my road, spread several inches thick and it didn't move much.

You could also check around and see if there's a woodturning club or high school wood shop in your area. If they agree to let you have some some of their wood shavings, take contractor grade/heavy duty large garbage bags and fill them whenever they have shavings. If you do a good job sweeping up, that may help your welcome. I usually wear a dust mask both sweeping up and when spreading unless I am upwind. Be sure to fasten the bag tops so you don't have shavings all over the vehicle. The mulch doesn't necessarily match for the first month or so unless you save 1-2 bags of the same wood and texture and sprinkle it lightly over all the bed, but once weathered, it will be fine.

Thank you for the great information! You are so helpful.

this might give you a better visual...ken

https://www.google.com/search?q=gorilla+hair+mulch&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiRuZSK_bzSAhVH04MKHYsfAnwQ_AUICSgC&biw=892&bih=739&dpr=0.9

NHBabs, thank you so much for your suggestions. My slope is a big larger/longer than yours but the grade looks similar, I think, so perhaps I'll give the mulch a go! As far as killing the grass first, will the Roundup be a problem for the incoming plants? I understand it has a short half life but I've never used it so I don't really know how it works. Would I need to worry about it washing down the slope and killing desirable plants below? And once the grass is dead, can I really just plant other things among the dead grass without them dying from the Roundup too?

IME Glyphosate kills just the things it touches and the herbicide moves from plants' leaves to roots. If you paint rather than spray the control is such that it is quite precise. With spray you need to be careful of overspray or drift that if contacting desirable plants can kill them. Even when spraying not near desirable plants I use low pressure, large droplet size and only spray when no wind. I largely use it for poison ivy that infests our fields. It doesn't have a long life and once dried on the plant won't create issues for other plants, though I wouldn't use it if rain is predicted. I've used it on field grass and once the grass had browned I mulched and then planted through the mulch without issues.

My slope is about 40' long and 15' down. It's planted with essentially just a tall ground cover (daylilies and Centaurea dealbata) and a few shrubs since it's on the back of the house, not visible to anyone but us and the farmer who plants the field. Insects enjoy the flowers and finches the Centaurea seeds.

Thank you Ken_Adrian, NHBabs and biondanonima fellow slopers! I forwarded the photos to our landscapers, will look for wood shops and/or order online and have delivered. I have been WEEDING without mulch as the BigBox stuff slides to the bottom making MORE work. Steep, unsteady slopes. Ugh. The worse one is over 2500 sq ft!! You guys are life savers. Thank you.

I want to thank NHBABS and Ken_Adrian for the lead on mulch that knits together. I was unable to get Gorilla hair mulch locally (NE PA). I ended up waiting for chips from 3 trees we had cut down, let the chips compost a bit and applied to the steep slopes. It rained later in the week, 2 inches, not a chip moved! Thanks for the help

I disagree with NHBabs. I mow the grass short but keep in place as it holds erosion and moisture. Then I spread overlapping layers of newspaper (better than cardboard), WET them so they lay flat, and dump free woodchips from any tree company. I may plant through it or wait a season. The chips don't migrate on my very steep slope. So, no chemicals, no money spent, no erosion. I am not the expert that Babs and Floral (see other post on similar subject) are, but I do feel confident in my method of planting a steep slope now.

I learned a very valuable lesson with my vinca project - we ended up killing (or so I thought) everything on the slope with Roundup, waited a couple of weeks to make sure nothing green came back, then planted the vinca and mulched lightly. The vinca has done very well, but unfortunately crabgrass has engulfed the entire slope. The vinca is doing just fine underneath, but pulling out the crabgrass is an enormous hassle. I have reclaimed about 3/4 of the slope bit by bit but I have now given up and am just waiting for a frost to kill off the rest of the crabgrass. I will have to put down Preen in the spring for sure. I absolutely should have put down a layer of newspaper/cardboard in addition to the mulch.

Furthermore, the Roundup application didn't kill deeply rooted things like docks and dandelions, so I have been pulling those out by hand, along with a few other pesky things like clover. I have a feeling this slope is going to be a huge weeding nightmare for at least another year, but the vinca is filling in much faster than I expected, so we shall see.

The mulching I referred to in my comment was on a 2500sq ft, greater than 30 degree slope. The tree chip mulch stayed! Knock on wood.

On a different 25 degree 60' x 20' slope, I planted bugleweed last fall. As prep we did 2 spraydowns with round up, but did not mulch due to delays in finding mulch that would stay on the slope, weeds were so bad I let the lawn guys weedwack it. My bugleweed is 3/4 destroyed. Today we weeded, applied heavy mulch. Will not plant again until weeds are controlled. The tree chip mulch stays in place where commercial mulch slides down.

This spring we did the above prep to a flat area 200' x 6', except I used a heavy layer of mulch. There were some persistent weeds that I spent a few hours pulling 2x during the summer. There is about an hours of weeding there now. Looks great!

I don't use newspaper or cardboard as I had problems in the past with mulch sliding off. I am sure either would improve results.

Mulch is key.

Edit: corrected slope degrees

I've given up on using V. minor for anything planned as it never seems to form a dense enough coverage to stop grasses seeding in and still wants to creep out everywhere I don't want it. That doesn't mean I've gotten rid of it though. I doubt I'll ever be able to totally eradicate it try though I might.

We use a lot of liriope, buy it in flats, 350 at a time. It is taking some time, but it is greatly reducing our weeding chores. But liriope is too high to use in some areas that are close to the edge of the woods and a large creek. Lots of creepy wildlife...

I found trimming vinca and ivy at the perimeter of the borders made it denser.