One more thing occurs to me, if you NEED some levelling. If that's the case, since you're only trying to combat potential erosion, you could use individual boards on edge that are attached to stakes securely driven into the ground in order to level up sections of the garden. Let's say, for example, that there is an 18" grade differential from one end of the garden to the other. Instead of creating an 18" retaining wall/device at the low end of the garden, divide the levelling into 3, 6" level changes. Plants can hide any unattractive structures since those would be low height. I would use the easiest, cheapest solution that does the job.

There's no reason you can't dig it up and move it. You can cut any of the plant, dig up the rooted area, replant. I have vinca all through a slope that also is overgrown with weeds amongst the creeping juniper. I have been pulling weeds and clipping juniper. Sometimes I make a mistake and pull the vinca. I just stick it somewhere else in the soil. And if you have too much, you can send it to me LOL! I'm having to use brush killer on the slope in spots where poison ivy and wild raspberry has taken over (in addition to the vinca, juniper and multitude of weeds). I'm not always accurate with the brush killer (and when poison ivy's involved I don't care!). so I'm sacrificing some vinca for the greater good. good luck!

I agree with Annie; setting realistic goals is important. Your budget is also a consideration, and how much you like to garden. What do you want the front of your house to look like? Do you envision a flower garden, a grassy slope,or a nicely landscaped area with a mix of shrubs and plants? My approach would be to Roundup the whole slope, after everything dies, pull out everything, then at least you'd have a 'clean' look. Then in the fall, as Loretta mentioned, do your planting. I think at this time of year, you're fighting a losing battle. Looking at your picture, it doesn't look like you have any edging material there, so I'd add some, till, add a fresh layer of topsoil, and start planting whether it's seed, sod, ground cover, or mixture of plants. Water regularly and the new plants will take hold, overwinter, and by spring those weeds won't have a chance. IMHO-If you choose the groundcover, stick to one type. I'd have a lot of fun landscaping your hill by adding some base plantings of a small tree or two, evergreen shrubs, rhodedendrons, azaleas hydrangeas, or some other plants then a stretch of perennials, and on the lowest part of the slope add ground cover. Mulch around everything. You'll have minimal weeding to do, a lovely look, and no mowing. I did something similar in stages over time(my kids were younger at the time)except I have grass at the lowest part, but if you go this route, it's important to put your ideas on paper first. J

Current update. Three hydrangeas and a Japanese maple (what a process to choose the right one!). Previous pictures probably didn't show the rocks that were in this bed. One had to be moved for the placement of the top hydrangea (that was fun). The grass nearest the lowest rock apparently is immune to glyphosate, so it'll be getting dug out soon. If it wasn't for the crazy heat this weekend, I would have been back out at the nurseries. Not sure on the spirea anymore since everything thus far is deciduous. Trying to supplement with some evergreen.. open to suggestions again or an update layout now that the space is more visible and coming together.. (so far considered a birds nest spruce(?) some sort of small yellow or golden mounded cypress / arborvitae (?) blue fescue (?) ..I like some contrasting colors. Not sure if something else flowering should be added (?) Thanks guys! (or/and girls!) It's going to look nice once it's fully planted and everything is mulched!