where can I get bulk top soil and mulch in Waco?
We do not recommend specific places for purchase, unfortunately. I would check around, locally, or try an online search for mulch in your area. Many hardware stores and garden centers will carry it.
planning to install ground cover in my back yard
That will be a soil with a pH of anything below 7.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/raise-acid-level-soil.htm
the boxes have been outside all winter - would inside box be too cold to plant flowers?
If you wait till after the threat of frost has passed, the boxes outside and the soil will warm up enough to plant flowers.
sing a clay mix. What ratio of the potting soil and I mix with my clay based garden soil?
Yes, you can use your own clay soil. These articles should help (There is a recipe in the second article):
https://www.gardeningknowhow.com/garden-how-to/propagation/seeds/when-to-sow-seed-balls.htm
gardeningknowhow.com/special/children/making-seed-balls.htm
I'm wondering if I can use an inground potting soil in my pots without adding ground soil.
I would not use topsoil or soil from the ground in container. Often, it is too thick to suit container gardening. Make sure to use a good potting soil, or amend the topsoil with plenty of perlite, vermiculite, coco coir, peat moss, gypsum, and other materials to lighten it up.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/types-of-potting-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/using-topsoil-and-potting-soil.htm
I've tried different ph testers in my garden like rapidtest, but never seem to see the needle move enough to convince me of the measurement. How long should I wait to make sure I'm not removing the probe to soon. ? Steve djtopcat@sbcglobal.net
I personally only use a full fledged soil assay every 7-10 years instead of some of those probes. The products you mention work differently so one has to review and follow the directions. If questions arise like yours, I would contact the company’s toll free number or send the question using their website’s “Contact Us” page.
I bought acidic soil for my hydrangeas which sadly just didn't do well at altitude/over winter. So I've hauled them out and starting again. Will the acidic soil I planted around them kill any future plants or should I completely empty the planters and start again with universal soil? thanks!
It probably depends on how sensitive the new plant is to acidic soil so research the plant(s) being considered. For example, hydrangeas prefer acid soil but will tolerate “some” alkalinity. As a result, you can plant the near lilacs which prefer alkaline soil. In your Zone 6b, hydrangea arborescens (in morning sun only until 12pm) and hydrangea paniculatas (sun tolerant so they can take full sun in areas with summers like yours) are very bloom reliable and winter hardy to zone 3; oakleaf hydrangeas are another possibility; they bloom on old wood, can be grown in morning sun (may tolerate a little afternoon summer sun but not like paniculatas) and are winter hardy to zone 5.