I mostly use raised beds for my vegetables but the truth is almost any plant can do great in a raised bed. Herbs, flowers, and ornamentals can all thrive in raised beds. What makes a raised bed an awesome growing method is the soil that it uses. You can mix the perfect soil mixture for any plant you want to grow whether it be ornamental or edible!
Herbs in a raised bed will want a well drained soil that isn’t too rich. Often herbs do much better when planted in a nutrient deficient soil so you don’t have to build a rich compost-like soil for them. For herbs a well drained mix is very important. Soggy soil can lead to rotting and the eventual demise for some herbs. They can handle conditions that are drier. In fact the flavor that herbs produce can be enhanced in dry conditions. When you fill a raised bed specifically for herbs consider adding sand into the mix to encourage good drainage – unless you have heavy clay (Clay and sand mix great together – if you want to make a brick!) For heavy clay soils add organic matter like it’s going out of style. If I were starting with a soil mix for herbs I would go about 2-3 parts of compost or soil to 1 part sand or vermiculite. Herbs are flexible and can handle variations in the soil mix. My herbs tend to get the leftover soil from other potted plants. They seem to enjoy the leftovers just fine.
Ornamentals are awesome in raised beds. I built a quasi-raised bed last year from retaining wall block and planted hostas and coleus inside. Perhaps quasi isn’t the right descriptor to add to the raised bed.
One side of the planting bed rests below the grade of the opposite side of the bed which allows the retaining wall blocks to hold the soil back, which of course does indeed make a raised bed. Indeed. I dumped a big load of homemade compost into the area and made some of the richest soil of any of my gardens. The coleus leaves became gigantic! I think they liked the compost, but who wouldn’t? …oh that’s right the herbs…
Raised beds let you control the soil characteristics. It’s not a bad idea to test the soil on occasional using your local extension service. They can do a complete soil analysis and advise you on on what to add to grow various plantings. Soil tests mostly analyze for edibles but many edibles need the same or similar soil conditions as the ornamentals.