I have a friend that has a hill in her yard that is full or rounded boulders and smaller rounded rocks. There is a rocky, sandy dirt between some of them. She asked me for suggestions for plants, so I'm asking here! I'm thinking sedums and hens and chicks, but I'm sure there's more types of plants that would do well there. This is zone7b, the site is in full sun, and has rapid drainage. Thanks for your help!

There are many plant possibilities!
Kinda depends what look she's going for...
If it is hot and humid some of the true alpine type plants may struggle there, but there are plenty of low, medium, and tall growing plants that would be happy.
I don't really have a guess where to start

Thanks so much for replying! Yes, we are hot and humid here. I went out to her house Friday to get a second look at the spot and to discuss what I've found out. She likes the idea of yuccas, sedums and hens and chicks, they all grow well here.
@DirtDolphins, any other plants that would do well? Summer temps are in the 90s, we do have winter cold, but usually fairly mild, it can get into the twenties, but rarely the teens anymore. Daytime winter temps usually in the 30s to 50s.
We do get a lot of rain here compared to Western states.
The soil does drain very well, it's kind of sandy.

although I have been called a dirty dolphin from time to time, that doesn't work to tag me!

I'm sure there are tons of plants that could work.
Does she want flowers? foliage? both? Will she irrigate some if it doesn't rain?
How big is the area? how big are the biggest boulders? How much space does she have for planting between them? and how deep is the potential root-run for the plants?
I mean yuccas get huge and make huge roots compared to semps

Personally, I like a variety of stuff--
consider the bulbs: early spring types--many little species tulips could naturalize and don't need a proper winter to perform well, allium loves a well drained soil-- some will fire in the early spring, most later spring, and a few in the summer and even later, fall bulbs--saffron crocus? maybe even some lilies?
Other creepers like creeping thyme and veronica? delosperma, dianthus?
Tanacetum densum ssp. amani, aka Partridge Feather loves shallow rocky soil--I know it grows in the PNW and handles the rain okay but I don't know how it would do there. It is indestructible here and very good at stabilizing slopes.
Irises

little dwarf conifers?
rock daphnes
salvia and agastache--many different kinds and some great smaller varieties

and a whole lot more exotic stuff

Hopefully someone more knowledgeable can offer some more ideas
She might be able to do more of the tender-type succulents if she's into those

She will take both foliage and flowers. And there are huge, medium size, and small boulders. She is willing to irrigate if it doesn't rain. There is lots of space between some rocks, very little between some. I'm not sure how deep the soil goes; I suspect it varies, deeper in places, shallower in places.
I didn't think about bulbs, I like that, I think she will, too. I really like the species tulips, I've grown them and love them. I'll check out the daphnes. Now about salvias, we can and do grow many different ones here; the ones that seem to do the best are the microphyllas, do they do well in dry conditions? I have a hot lips that is huge; I whack it back twice a year, but I find it to likes to be watered on a regular basis. Agastaches do rather meh here, perhaps they need hotter and dryer? I'm really sorry I messed up your name! Thanks for all your help, I'll do some more research.

I garden in similar weather and have been experimenting with rock garden plants the last few years. I have particularly been trying out a bunch of classic 'alpine' plants, which look great among rocks, but are often small stature - and many of them don't tolerate our summer heat & humidity. There are plenty of native plants which appreciate sun and well draining soils, which would do well also. They are likely to be less fussy. I bought a nice selection on-line at a missouri native plant nursery. They have done really well. Linaria purpurea and Asclepias tuberosa both arrived via some birdie - both do well in full sun and good draining soil. Barbara's buttons (Marshallia caespitosa), Amsonia hubrichtii, Pulsatilla vulgaris, Icelandic poppies, Silene virginica.

I second the recommendation of dwarf conifers - they look amazing in a rock garden.
But in my area, Abies, Tsuga and Chamaecyparus need a little afternoon shade to survive our summers.

Among the smaller alpine plants, among the ones doing well for me are:
Rock garden daphnes - there are many sizes. All flower beautifully w nice fragrance.
Creeping plants include thymes and veronicas, which are generally easy and nice spreaders. And many of the dianthus cultivars should thrive in your area.
Erysimum kotschyanum is another cute alpine creeper with bright yellow flowers.
Dracocephalum argunense & D. grandiflorum have grown well.
Alyssum oxycarpum is a flat creeper with grey foliage and yellow flowers.
Myosotis tergluoense and Houstonia caerulea have bright true blue flowers.
Aubretia gracilis has beautiful purple flowers.
Arabis x sturnii is a creeper with purple winter foliage.
Saponarias do well - several species available.
Horminum pyrenaicum.
Helianthenum is a shrubby plant which favors sharp drainage and has beautiful bright flowers.

I realize this is sort of a rambling list - I'm sure there are many others.

I suggest looking up these plants in the plant database to find something you like.
I buy most of my plants on-line since the variety is much better than you'll find at big box stores.

Dianthus don't do very well here, they only look good in the spring, it's just too hot for them, I think. We grow lots of Asclepias Tuberosa, common as cat dirt. I do like the look of Barbara's buttons, a good looking groundcover, Ill recommend that. I do like the daphnes, too.,

Well there are a few hundred different species of dianthus--some are much better suited for the task at hand here!
Maybe if you can find the tight hummock producing types you might want to suggest she give one a try. They aren't exactly spectacular in the spring or the summer, but, I really like the green mounds in the rocks--like this one

We get plenty hot here, high nineties--low hundreds, and many of them do well here

Now those kinds would work very well! You know I never though of dianthus plants that would be like that! Seems like I have a lot to learn......

gardenfish said:
...Now about salvias, we can and do grow many different ones here; the ones that seem to do the best are the microphyllas, do they do well in dry conditions? I have a hot lips that is huge; I whack it back twice a year, but I find it to likes to be watered on a regular basis. Agastaches do rather meh here, perhaps they need hotter and dryer? I'm really sorry I messed up your name! Thanks for all your help, I'll do some more research.

Lynda, There are some hardy salvias that do well in dry conditions, although I'm not sure how well they tolerate humidity. I recommend checking out the High Country Gardens website. They specialize in xeric plants, and although their focus is the southwest, I notice reviews from people all over the country. They're good about giving honest advice. As for agastaches, I've struggled with several of them here to find the perfect balance of light and shade. Some definitely struggle in full sun. I'm also in zone 7b, but entirely different climate.

Penstemmon pinifolius might work well in a rock garden. Check it out at High Country Gardens and then you can browse from there. I have abused mine by moving it several times over the years (bad mom!) but it keeps going with minimal care.

https://www.highcountrygardens...

Zoe, you've read my mind! I'm familiar with High Country Gardens, I was thinking about sending it to my friend. I really like the look of the pinifolius; I have seriously thought about getting one for myself! Several different varieties of penstemons do well here, although the ones folks usually grow here are the ones that need more water. I grow lavender, so I thought I could plant the pinifolius next to it. I hardly ever water my lavender.

How about some alpine plants are perfect for rock gardens. A few I have grown iDianthus (Pink), Phlox subulata (Creeping Phlox), Aubrietia (Rock Cress), Euphorbia (Spurge), Stachys byzantina (Lamb's Ears), and Helianthemum (Rock Rose) create an eye-catching display. The garden explodes in a firework of colors for months and requires moderate care. Lewistas pink collection is my absolute favorite.

Look them up and pick what you like and leave the rest. All need fast draining soil and part to full sun 6 -7 hours a day.
Happy planting..

I love Lewisia and have tried it a couple times but it can't handle our humidity.
I've also tried Penstemon pinifofolius a couple times - it seemed to tolerate my humid summers OK, but I couldn't get it to overwinter. Maybe just not hardy enough. It might do better in Arkansas.

Thanks, Bea and Scott, some very good suggestions!

SL_gardener said:I love Lewisia and have tried it a couple times but it can't handle our humidity.
I've also tried Penstemon pinifofolius a couple times - it seemed to tolerate my humid summers OK, but I couldn't get it to overwinter. Maybe just not hardy enough. It might do better in Arkansas.

The P. pinifolius overwinters here, also 7b. That's why I recommended it. Although...we might have the same temperature ranges, but our climates are entirely different!

P. pinifolius does well here, and we get plenty cold.
In general, I find the Penstemons not to be very long lived as compared to other perennials, and they like to wander a bit and some are very promiscuous, so there's always a few surprises, some of which are quite nice
Anyway--the thing that does them in is wetness in the cold weather when they are dormant. Here we get snow in the winter which isn't rain and isn't actually wet until it melts...

I'd always heard that lavender doesn't tolerate humidity...if you can grow lavender Lynda, then your friend might wanna check out the dwarf lavenders that HCG offers--I love them!

Here's a pic of a section of my driveway rockpile around the end of May--it is such mayhem, I call it the fruitloop effect

contains many of the plants mentioned...
The reds, Helianthus 'Ben Ledi' at the left (turned into quite a shrub!)...P. pinifolius 'Compacta' at the right by the car

There are several different dianthus and penstemon varieties in there, salvias lower left all volunteer bee-seedlings, tanecetum is the silvery stuff at the base in the center, and creeping thymes, dwarf lavenders not blooming quite yet...
here you can see one behind the campanula

I don't think anyone has mentioned that yet, but the are several decent campanulas to try.
This thing is a cute little mat-form of Ziziphora clinopodioides


and just to make the point that a person can do anything they want in their rock garden--a mini rose

Dirt, that is so enviable it makes me want to tear out my entire garden and start again! What part of the country are you in?

Lynda, that there is a perfect template, or at the very least, all the inspiration you need. In my opinion, anyway.

Thank you Zoë!
I am in northern Utah on the skirt of one of those very rocky mountains.

I'm currently in the process of ripping out what I call the north-40--not really starting over but almost--clearing out a lot of stuff to make room for my latest plant addiction
Normally, I'd say, jeeze don't do that, but, since I am doing it, I don't feel right saying that at the moment, sometimes ya just gotta change it up I guess
Really, I am making it worse right now, in the overall grand scheme of things can't help it though, I am nutty that way

Wow that's some fancy gorgeous 'rock pile' as you say..
Every plant is very happy . What a great example of how a rock garden can enhance any garden.

@Dirtdorphins, Show me the rule that says you can't change your mind! I call it "rearranging the furniture."
What's your latest plant addiction?