The worst thing you can do is remove all the mulch and pull all the weeds leaving a steep hillside of bare dirt above you. Don't do that.

The weeds look like a clover which is a mighty fine soil stabilizing groundcover. Weed whack it so it is mowed and green and looks just like a lawn.

After you have decided how much you actually want to really have and maintain a garden on this steep slope and have developed a well thought out landscape plan then you can start planting things. Removing the mulch and pulling the clover is not likely to be a requirement for that.

Well, shoot. I already pulled 90% of the clover and removed the much. Would replanting ground cover immediately help reinforce the slope? I got nervous today when I noticed how crumbly the slope was and immediately stopped.

The chances that you got rid of the clover by hand pulling are nil. Let it grow back.

I see trees; do you get much sun? You might want to consider some low-growing native plants that would suit your conditions.

With no ground cover the first rain will wash a lot of your soil, downhill. Born and raised in So Cal.

I still have the old much bagged on the side of the property waiting for pick up. I'm thinking that I redistribute it, come up with a plan and tame my excitement to dive in :)

You need to plant with a drought tolerant, low, spreading plant, so the roots can hold the hillside. Put in some sort of barrier between the clover above and the area you're planting, so the clover doesn't continue spreading. It depends on how much sun or shade you have. The area closer to the retaining wall can be a variety of plants, but you need a good large cover for the rest. Ceonathus grows very quickly and is evergreen, but you want a low variety, and need to reduce the height every few years or it becomes a haven for rabbits. Take the photos to a local nursery for suggestions.

The clover will grow back. Enjoy your new home.

@sealavender There are two massive pines (over 80Ft) at the top of the slop and to the side. I was thinking the same but it sounds like I need a pretty complete plan before messing with the slop anymore.

@sealavender and to answer your question we do get a lot amount of morning and evening sun. The pines put us in the shade during the day.

@Linda Thomas Thank you for your help :)

Those pines are notorious for blowing over in strong winds. I would have an arborist look at them before you do anything else.

Can I just mention that the 'clover' is actually an Oxalis species, not a Trifolium. So if you are researching look it up by its botanical name to get accurate information. Oxalis are incredibly difficult to eradicate so you might as well live with it imo. You may think you've pulled 90% of it but believe me, you haven't got rid of it. It'll be back. And for goodness sake, don't throw away that spare mulch. It would be like throwing away money.

I commend you on the effort. I had a steep, mostly Decomposed granite slope when I lived in So Cal. I used Rosemary as a ground cover. Its low water, very tough, will grow in shaded areas, will choke out your clover and the pine needles won’t do anything to it. And it’s fast growing and your soil looks a lot better then mine was. You should have your trees trimmed by a tree trimmer. Pine trees are a pain. Do the lower part first and then move your way up. I would use a good weed eater on the weeds, it’s a lot easier. Spread the mulch back on the slope, buy a couple of flats of Rosemary or GC plant and do a little at a time. Good luck. Btw, are you in North County, San Diego?

You are basically working without any plan, which makes the work seem somewhat pointless. You might possibly be wasting effort, or worse, causing harm, for which you must expend more effort in order to correct the the work that has been done. The first thing to do is to assess what's there. The second thing is to create a plan for whatever transformation is desired. (This requires making a base plan, developing schemes, conceiving concepts and refining these ideas into a final plan, which you will implement over some period of time, according to your resources and budget.

Those of us who have done this kind of work before might secretly laugh at what some people call, "pulling weeds." More often than not, they're really just pruning -- leaving all the roots in place so that in short order, the tops reappear, looking more vibrant than ever. A common misconception held by some new to the field is that by intentionally installing some plants, those plants will keep undesirable plants at bay. Usually, the latter win out and take over. If you go through the process of assessment and planning, you'll be in a much better position to deal with what's there and turn it into what you want it to become.

floral_UK is correct, your weed is an oxalis that is pretty much everywhere in southern CA yards and open areas. The bad news is that it's very hard to eradicate as has already been said. The good news is that it's seasonal. It starts growing with the winter rains and dies and goes away when things start to dry up and heat up around May or June, then it is gone until the winter rains return. Secondary good news is that, as you have already discovered, it is very easy to pull out or weed out with a cultivating tool. Just remember that pulling out the green growth does not mean you've eradicated it.

Check out my plan for the yard @wacokid @calidesign @Yardvaark. I'm going to reuse the mulch I pulled up and add a rock section with a feature agave.

I like it, fits in with what you have and you are already close. Good job and here's a little inspiration to get you going.

https://www.youtube.com/watch?v=YWNi4xfZYO4

@gardengal48 (PNW Z8/9) agree and I understand what @Yardvaark is saying. I think he means don't get bummed out when they come back. It is much sunnier than it seems. 9 - 12 months its full sun.

You will never be able to get rid of all the weeds on your slope Kevin, you just have to contain them. You could leave the ones at the top for now and just mow them down until you get up there. Rosemary will grow and fill in your slope very well and fit in with the plants that you have. You will need to use a weed eater every year or two to keep it low, if you want. And it's great to have for a spice in the kitchen or on the BBQ. Or use another ground cover of your choice. Your plan is good, a little at a time.

And Kevin, you are the best to judge how much sun the area receives! From the photos it just looks rather shady.....too shady for rosemary. But likely enough for the agave - even mine is not in full, all-day sun but not necessarily in much shade :-)

I'm not an expert on California plants so I won't comment on choices, but for slopes in general, here are some tips.

1) As others have said, choosing native plants that spread quickly will help hold the soil in place and prevent erosion.

2) Keep general maintenance in mind when choosing plants. With a slope that steep you likely will want minimal maintenance so you don't have to drag your weed wacker, lawn mowers, wheelbarrows up the slope.

3) Low water/drought tolerant plants are not only better to prevent erosion but provides less risk to the integrity of your retaining wall.

4) When you place boulders bury them in 1/3 of their mass to avoid rolls.

5) If you use rock mulch at all, stick to angular rocks ( not river rock or peagravel) to avoid rolling and slumping.

6) Choosing smaller pot sizes for planting is often easier for planting on slopes, since a smaller hole is needed for the root ball. The link below has an example of a planting detail for slopes. Notice how the stem is not covered, and that the downhill side has a bit of a berm built up to provide enough soil cover for that side of the rootball but also to hold and slow water.

https://landscapearchitecturemagazine.org/2018/04/24/slope-style/

Waco. Your attacks on people’s character is getting out of hand.

Your plan looks okay but you also need to add plants that will better hold and completely cover the soil to help with erosion and to keep the weeds down. The mulch will be gone the first season on a slope. If you have sun, rosemary (the low growing variety) or creeping thyme are great.

Gardengal, thanks for those kind words. You must have had a glass of wine at breakfast. :-)

Yes, Kevin, that's what I'm saying ... don't expect the Oxalis to remain gone. They will likely be all mixed in with whatever you plant. It's not that they couldn't be gotten rid of, but it would require chemistry, and given that you've hand pulled so much already, I'm thinking you're not open to it. The alternative will be living with them for eternity. They might also be the groundcover of opportunity that you wish to take advantage of on account of their easy accessibility.

Some of what's in your plan is not clear. If those are rocks dividing various areas, I'm thinking you'll eventually think them not worth the bother of installation. I'd avoid creating wedge shaped areas as they are good for nothing and hard to maintain.

I once had a steep slope in size like yours in zone 8 that I planted with 24 flats of 2.5" pots of Hypericum Calycinum, the stoloniferous ground cover St. John's Wort. When I planted each one I dug back a little "shelf" to plant on level and mulched with small gravel, the jagged edges will compact into the soil and hold it, not pea gravel, that would roll off. The plants beautifully covered the slope. I had minimal upkeep, I also gently watered overhead when the plants were starting out to keep the soil moist and not let it dry out completely so that any rains wouldn't start washing away soil. Think of how a sponge works, when it's moist it holds water, if it's completely dry the first water that hits it wants to run off. The key was in how the plant spread with stolons to lock in and that it grew fairly quickly, also that I started with many, small plants. Right plant, right place. I wouldn't plant anything that grows aggressively (like Ivy) it would too soon become a nightmare to maintain. I think St. John's is good up to zone 9. If you can't grow that, look for another stoloniferous evergreen ground cover. Just my 2 cents.

I wouldn't recommend H calycinum. It's an aggressive spreader and not much to look at. Really hard to remove if you get fed up with it.