Yes, they will affect the PH...
I don't know Texas soil....but I sure wouldn't add rock anywhere....add organic material instead...improves drianage and fertility as well....and acts as a buffer to keep the PH near 7.
Linda C

However, if you've bought them...there are many nice plants you can grow in alkaline conditions. Think lavenders, Dianthus, various shrubs.

Lindac has it, though. More humus. And if you're gardening in a hollow of some kind - raised beds.

depending on their hardness- yes, they certainly can...

and unless you're double-digging your bed, and using these as an underlayer, they're liable to cause you additional headaches, especially if this is going to be a bed you're going to be adding to frequently. sharp sand is better for drainage in most cases...but medium-ground mulch (not the huge wood chips, but not the triple-ground either- I like the stuff that comes free in big piles from some of the local townships, or tree services) is the best ammendment you can get - evens out the water distribution, aerates the soil, ultimately increases the nutrient count of the bed, and you don't have the tiller flinging pebbles at you :)

Thank you all for your responses - at least I know I was thinking correctly. I'm learning!

chinacat - i HAVE added mulch at the bottom of the raised bed - but I heard it can leach nitrogen from the soil as it decomposes? My neighbor cut some limbs and ran them through a shredder. The mulch has been sitting at the bottom of my bed for 4 mo's. How do I know if it's ok to plant plants w/o it sucking away the nitrogen?

and good point re: the tiller. but isn't that why i ask my husband to do it? ;))

The amount of nitrogen leached from chipped wood is teeny....miniscule....easily compensated by an application of an organic source of nitrogen....like blood meal, alfalfa, composted manure etc.
Rocks in your garden are never a good thing. People spend big bucks to get them out of their garden....
Linda C

Allow about a year for woody mulch to break down. More if you experience sustained dry spells in your location.

And if it is buried under soil - allow longer. It needs greeen stuff and/or a high nitrogen fertiliser plus AIR to really get the composting process moving. Aerobic vs anaerobic.

In general it is desirable to have a small rock population in the garden. There is something daunting about plunging in a spade and hitting the hard stuff. However, rocks can also direct water to where it may be better used. They help the ground to warm up early and they can hold heat to make a microclimate for tender plants. Not all bad.

And, if it's not too late (never!) you might want to use your rocks to construct an elegant drystone wall for growing limelovers.

if you have really, really dead soil (no ants, no worms, compacted subsoil) then the nitrogen thing might be an issue...but it sure wasn't in my hardpan front yard, though at worst, if you're concerned, linda's got it on the nose.

if you're the chemist-brat that I am, half a cup of ammonia in five gallons of water is more nitrogen than it will ever need. better to add grass clippings, aged manure, and maybe some newspaper to the mulch.

my garden gets about an inch deeper every year - and I add four inches of mulch in the spring, maybe another two over the course of the year (top dressings when I add new plants) and then four inches of leaf mould in the fall (while everyone else is bringing leaves to the recycle station, I'm shovelling the stuff at the bottom of the pile into trashcans to take home with me :)

Sarah,

Please before you do anything else to your soil please read my suggestion.

As you know Texas is very large with hardiness zones from 6 to 10, and the soils range from very acidic to very alkaline. You say that your soil is already alkaline. If you have not already done so, then I would highly suggest that before you do anything to your soil, contact your county extension agent and ask to get a kit for a soil analysis to be sent off to Texas A&M for analysis. It does not costs much, and it can save you a lot of money in the long run.

I don't know where you live, but if your home is an older home your soil might have already been amended by a prior owner. My owner added wood ash to this yard which was the worse thing she could do since we live in an area that already has high levels of phosphorous and potassium. And since I live on a salt water bay, I have lots of salt issues and mainly an all sand yard.

At our Master Gardener demonstration gardens, I took two soil samples from two separate raised beds. It was very surprising to see the different soil readings between the two beds that were four feet across from one another. We had to amend the soil before we could plant anything.

Try contacting either your Texas County Extension Offices or contact TAMU. They can give you lots of good information about your soil after you get a soil analysis completed.

Thank you all for the advice! I'm glad that I'm learning so much!

FYI - I live in Dripping Springs (west of Austin). Lots of calicche (what fun!)