Where are you? Location makes a difference as to what would be suggested.

It is also best if any weeds and grasses are removed before any planting. NO groundcover establishes rapidly enough to smother existing vegetation and you will be battling it from now on unless it is removed completely or killed off. And even when fully established, few GC's will completely defeat any weed growth.......it will certainly be reduced but nearly impossible to prevent any recurrence.

What do you mean by 'ground cloth'? Landscape fabric/weed cloth or a geotextile intended for slopes

one to consider if you are in the proper zones: Ceratostigma plumbaginoides. Despite the fact that it is deciduous 3-4 months of the year, its beauty & erosion control ability make it a winner.

Doug, most people would want an evergreen groundcover for a hill side area of that size, rather than deciduous.

Cotoneaster dammeri 'Streib's Findling'. Do not ignore the advice given above.

Anything less than 2 ft. deep will need some continued weeding on top of the same shared need to be started out in clean ground. In my part of the Northwest quite long-established plantings of kinds even as thick as Tamarix juniper may still have ongoing problems with alder trees, blackberry plants, giant morning glory and the like getting going in them on some sites.

I wasn't clear that we intend to use heavy-duty weed cloth. We've killed the weeds and grass with first application of Roundup. Going to do a second application followed by pre-emergent. Was hoping to find a fast-growing evergreen plant that will look good year-round. It doesn't have to have flowers. We're in Oregon City, Oregon, hardiness zone 8A. The picture doesn't show how large the area is, but we measured it; over 15,000 sq.ft. Appreciate your feedback!

Do not use heavy duty weed cloth. That is a colossal error. Do not use preen on a new planting. That is a huge error. Preen inhibits root growth the very thing plants must do.

Kill the existing vegetation. Looks like you did a good job on that, Cover the slope with a thick layer of mulch. Tree trimmers woodchips are the best. Plant your groundcover. Yes there will be some weeds to pull as the groundcover fills in. This will happen much faster when you Do Not cover the soil with a water and oxygen repelling fabric or lace the soil with root retarding poison.

The Cotoneaster dammeri 'Streib's Findling' may be a great choice for you. It stays flat as a pancake and roots along the stems as it spreads to form a solid mat.

Question. What is the remaining groundcover on this slope?

I'd look into something like Lonicera pileata or Genista pilosa. Not the most common of groundcovers but fast growing, wide spreading, evergreen, drought tolerant once established and deer resistant. And both will produce a pretty thick blanket that will keep weed development to a minimum. Will need to do some minimal weeding until they fill in.

The lonicera is a Great Plant Pick so well-recommended for the PNW.

ETA: 'flat as a pancake' is not gonna keep the weeds down....thickness is :-))

Christopher, thank you for the good advice. The hillside is too steep to do any weeding. We've tried it, and we both hurt ourselves pretty badly. I do understand your advice about not using pre-emergent before planting. Don't know if a 30-degree slope will hold the mulch. Going to check about the growth habit of Cotoneaster. Whatever we plant, it's going to be spaced very closely to get fast, maximum coverage. The other ground cover we used is Ceanothus "Point Reyes," which is gorgeous, but it was a mistake because the grass and weeds grow profusely, even with 2" of mulch around each plant. Maybe it's time to call a concrete pumping service and call it done. I'm really frustrated!

GardenGal48, we do have lonicera trained on an espalier. I've thought about using it for the hillside. I wanted something relatively low-growing, so we can plant bushes and small trees for visual interest (and to hide the neighbors' home below), but may have to re-think that priority. #1 priority is to kill the weeds and grass and keep them to the barest minimum possible.

Diane I live in the mountains of Western North Carolina. That slope is mulchable and weedable. More difficult, yes.

This is a slope I planted last fall as described. The Cotoneaster is the lowest tier of plantings closest to the Almighty Falls.

The suggested honeysuckle is a spreading evergreen shrub with small leaves and not a flowering climber.

Blankets of low-growing cotoneasters are not very suitable for being walked on yet often need to be kept weeded to at least some extent into perpetuity.

'Streib's Findling' belongs to Cotoneaster procumbens rather than C. dammeri and may actually consist of one or more clones of the typical species - to which it is very close - rather than a completely distinctive horticultural form.

Not that it matters much, but Monrovia Nursery and the bulk of internet links list 'Streib's Findling' as C. dammeri. Maybe the botanist in charge moved it back to C. procumbens and I missed it. Either way I am talking about this specific selection from Monrovia, the key being it is a super short, evergreen selection. Cotoneaster is a big genus. There are plenty other cultivars that are similar.

https://www.monrovia.com/plant-catalog/plants/1006/streibs-findling-cotoneaster/

This is C. dammeri 'Streib's Findling in action. Thick enough for you GG?

So shoot me. There are a few weeds to pull. I'm still searching for that magic no weeds ever groundcover. The ferns I leave. I'll get around to it at some point and won't be the least bit afraid to step right on it if need be. Far worse things have happened to it.

As far as it goes 'Streib's Findling' bears no resemblance to Cotoneaster dammeri. Various other species in the genus have also been grown in western gardens under the wrong names.

Cotoneaster dammeri is used frequently as GC in this area - in fact, I've spec'd it on a number of projects so I am pretty familiar with its attributes. I have never had it grow very thick or dense even when fully mature and well established. Weeds will penetrate the area easily.

OTOH, the lonicera will develop into a solid green mass a foot or more thick. And pretty rapidly at that. I used it on a beachside landslide remediation project for a pretty steep slope and it handled the situation beautifully! But because of the size and thickness of the mature plants, it is not a GC that will accommodate other plantings well, unless they are placed at the edge of the planting area (top of the slope?).

It would seem to be a matter of deciding which is of highest concern - having few, if any, weeds to contend with or a more designed, integrated planting that could be prone to typical weed development.

My experience with steep slopes is that the previous owner of my place planted English ivy as a erosion control ground cover on a very steep slope. In many places steeper than yours. But even the very invasive English ivy is no match for other weeds. I have salmon and thimble berries, red elderberries, Indian Plum coming up through the ivy and shading it out. Even some non-natives like European ash and European beech trees sprouting out of the ivy. The worst is our native PNW salal, Gaultheria shallon, when all its needs are meant they win out over ivy. So any ground cover that isn't as aggressive as these will be full of weeds given time and no weeding. Maybe a good weed block or engineering geotextile fabric with lose bark as a cover would last the longest without weed problems. I covered a smaller area doing that and it took 16 years before weeds started growing on it, but with the bark they were easy to pull out.

I appreciate your feedback! One of the "weeds" we have is an introduced blackberry, that will grow anywhere.

I also have problems with the Himalayan blackberry - Rubus armeniacus which comes up through any ground cover plants, ivy or salal. Another big problem is the PNW blackberry - Rubus ursinus. Its vines crawl and cover whole plantings of ground cover much like morning glory except it has nasty thorns so you have to wear leather gloves to remove it. The other blackberry that isn't native, Evergreen blackberry - Rubus laciniatus isn't as aggressive as the other two, and I have never had problems with it in plantings that have covered the ground from sunlight. I have found it growing in open areas but it doesn't send out long canes like the Himalayan or the native blackberries.

Typical height range for the honeysuckle is 1 to 3 ft. A small grouping I made on Camano Island may be about 2 ft. tall at this point.

This material was obtained as the typical plant, perhaps raised from seed. With a percentage of clonal selections I have seen on the market having a more flattened- and low-growing appearance - at least in nursery sizes.

The Camano plants are quite dense, have been for years. This makes me think similar forms of this species could be quite a good choice for the situation asked about here.

Thank you! We've been thinking about honeysuckle, too. Going to put it back in the list of plants to consider.

Note again plant being talked about is Lonicera pileata specifically. Except for botanical details small-leaved evergreen shrubby kinds like this are not anything like the familiar flowering climbers.