So you want to grow an herb garden:
You are in luck if you want an herb garden and you live in Central Texas. Most herbs do very well here. Some herbs considered tender perennials elsewhere are hardy here in zone 8, including rosemary, oregano, sweet marjoram, lemon balm, lavender, and bay to name a few. The main question is what kind of herbs do you want to grow? Do you want mostly culinary herbs to cook with, or are you interested in health remedies, or both? Herbs like mustard and horseradish can be used for both purposes. Some herbs are mainly used for potpourrie like lavender, and the scented geraniums. Although the flowers may not be much to look at, it's a joy to work amongst them because just brushing against the leaves releases marvelous fragrances.
If you want a culinary herb garden, that is easy. Most are short, and you won't need a whole lot of space, although you will have to give yourself about 8 foot square if the plants aren't potted, because even lemon thyme which only grows about 8 inches high, will spread out several feet in circumference. If you don't have that much room, you might consider growing your herbs in large pots. They won't grow their full natural spread, but you will be able to cut from them for cooking, just not as much. The problem with potted gardens in Texas is the heat and wind. You will probably have to water them at least twice a day, and add a little liquid fertilizer once a month. In the garden, most herbs are naturally rather drought tolerant, although you will have to water them at least once every three or four days when it gets very hot, dry, and windy. It will help a lot if you lay down heavy mulch around them.
You can mix your herbs in your flower beds and they will blend in very well there, because they are all different heights with interesting leaves. For instance, some of the basils have purple colored leaves and flowers, and culinary sage has beautiful silver colored leaves. Just do some research first before you plant because they grow to all different sizes from several inches tall like lemon thyme, to the bay tree which grows to 40 ft X 30 ft in good conditions. Lavender and rosemary are both familiar landscaping plants in Texas, and most people here know that they are shrubs. Dill, parsley, cilantro, and fennel all get several feet tall when they go to seed, and their white, flat, 'Queen Ann's Lace' type of seed heads will fill in very nicely amongst your perennials of similar height such as your purple coneflowers. Some herbs are perennial, some are bi-annual, and some are annuals, which will die every fall, such as the basils, and you will have to replant them each year.
Also do a little research before you start to find out their water requirements. Lemon balm is really a mint, and will do best if it gets adequate water and some shade in the heat of the day. It grows to be about 24 in tall, and makes a nice ground cover around trees and things where you don't want to mow. Lemon thyme, on the other hand grows only about 6 inches tall and you can grow it as a ground cover under your roses and smaller shrubs. It likes sun, and you can use it around stepping stones because it doesn't mind being tread upon which will release a wonderful lemon fragrance. The only problem with that is that bees like it, too.
Well, bees are part of a garden, and without them we wouldn't have much of one. Most herbs in flower will attract wasps, bees, and butterflies, which is a plus for gardeners. Once a man came to me once and wanted to know what to spray his butterfly bushes with to rid them of wasps. He had planted them along his sidewalk, and they attracted flying insects like they are known to do, hence the name 'butterfly bush'. His granddaughter was terrified of wasps, and he wanted to prevent them from visiting his flowers and frightening his granddaughter. I had to tell him that the only thing to do was to teach his granddaughter not to be afraid of wasps, or else to move his butterfly bushes somewhere else. As you can see, you must consider this also when planting your herbs. The garden should sing, hum, and move, and be fragrant, for the land is breathing and alive, and the joy of the garden is that it reminds us that we are just a part of the whole living, breathing, planet Earth. Herbs help the garden do just that for bees and butterflies love herbs as much as we do, and will grace your garden with color and a happy hum. Parsley, dill, fennel, and cilantro will raise the most gorgeous butterflies like the swallowtails, if you don't mind the caterpillars eating them up. It's great fun to watch them grow, become chrysalis, and then hatch out into marvelous butterflies that float in and out of your garden tasting its nectar.
By the way, many garden flowers such as the purple coneflower (Echinacea) are considered herbs because they are edible and the leaves can be used for making healthy teas, and the common violet, marigold, and hibiscus flowers are very nutritious too. This brings up the subject of using herbs for medicinal uses. The fascinating thing about herbs is that they have been used since ancient times for both cooking and medicine. But be careful in trying out herbs medicinally. Herbal guides are not accurate in their dosage, and varieties vary in essential oils, so the best thing is to only use familiar ones such as chamomile or lemon balm that we commonly use for teas. Get a modern book and learn which ones are safe. Many of the herbs listed in old herb guides are powerful and can be deadly. Those ancient monks had practiced on a lot of people before they could use some of them more with a modicum of safety.
The thing about herbs is that they are useful, fragrant, and have a very long history of relationship with humans. Have fun with herbs, learn about their ancient history, enjoy their fragrance, and learn to cook with them. Fresh herbs do wonderful things to ordinary food. Growing herbs is a fascinating hobby and can bring much joy into your life.