Yeah, here just east of Housemouse, it hasn't been great for gardening. WAY too much rain- like, 18" more than usual!
But the garden actually looks pretty good despite that. Lots of organic matter helps, although I don't get as much manure spread on the garden as I'd like. Which is ridiculous, since I live on a dairy farm, and have horses and chickens besides.
The only real problem with fertilizing herbs a lot is that they *may* get too lush and prone to mildew or fungus, especially if you live in a very hot, humid climate. Also, it *may* "dilute" some of the essential oils, and they might not be quite a pungent or potent. But mints and lemon balm and many others thrive in rich soils, so don't worry much about it. Just don't pour on the fertilizer...
Willow- about combinations of herbs... pretty much whatever you think you want to try. As others have said, the mints will spread like crazy (they spread via underground rhizomes), so you want to be careful with them. I stack two smaller tires and plant black peppermint (the most pungent kind- peppermints do NOT breed true, so you need to find plants at a nursery if you want to be sure of getting a "good" type. Snitch a leaf and crush it, then sniff and taste- if it tastes good to you, buy it!) in them- and it has spread a bit, but we mow around the tires, so it can't go far.
Lemon balm will also spread a lot- mostly from seed, though, so if you really don't want lemon balm plants everywhere, just harvest them a couple of times, and once more when they start setting seed. I don't mind- they put seedlings into the lawn and we just mow them. Sometimes I get a clump in a nice spot (I've got two thriving volunteer clumps beside my greenhouse door) and I leave them grow.
Oregano (if you can, buy some seeds of Greek Oregano from Johnny's Select Seeds- it's wonderfully pungent and spicy) will crawl and spread- but pretty slowly. Marjoram has the same type growth habit, but probably won't survive your winters.
Chives (they're available in both onion and garlic flavors) make larger clumps every year, and may put some seedlings out, but they aren't aggressive. They work nicely in the midst of the herb bed- the oreganos can climb around them.
Thymes have similar growth habits to oregano- low and sprawling.
Rosemary is an upright plant- like a small bush- usually. There are some prostrate varieties, but they're rare. Tarragon (you want the FRENCH variety- you'll be disappointed in the Russian) grows almost exactly like Rosemary. Rosemary is a tender perennial- if you want to keep it from year to year, you need to pot it up and bring it inside. I prune mine down hard and stash it in the root cellar for the winter. Others will turn it into a windowsill herb and use it for cooking.
Catnip and spearmint are both taller, more upright growers than peppermint- mine get close to 3 feet tall! You definitely want them in the back of the bed! They both will spread...
Sage is a woody perennial which gets at least 2 feet tall. It doesn't spread very far, and is another which could be planted with some of the crawling low herbs around it.
Parsley is a biennial- it will come back next spring, but only for a few short weeks before it sets seed and then dies. But quite often it will self seed and you'll have more for the next year.
Lovage can be a great herb for seasoning if you've got room. It gets 3-4' tall, and can really grow into a large clump. I'd give it a tire all it's own if you ever start it. It's a perennial and comes back bigger every year. It's wonderful dried in various herb mixtures and an herb salt that I got from an herb book years ago. If I can find the book, I'll post the recipe.
Medicinal herbs are an entire subject to themselves. But two I wouldn't want to be without are skullcap- a perennial which I start from seeds I got at Johnnys. It spreads as well, but is easily eradicated, unlike the mints. It's THE best "nervine" and tranquilizer I've ever found. I've given it or recommnded it to many people over the years, and I don't believe I've ever had anyone tell me that it didn't help.
The other one (there are actually probably a dozen that I simply HAVE TO grow) is Calendula. Also known as Pot Marigold, it's an annual flower that you can grow in your flower beds and no one will ever thing you're growing "medicine". It puts out pretty orange and yellow flowers in various shades from midsummer to frost. The flowers are an excellent anti bacterial- I use them in an "anti infection" soak that I've seen cure some really nasty infections and cellulitis. They are also soothing to the skin, and make a wonderful addiiton to skin creams and lip balms.
And if you can find room, this fall get a few cloves of garlic and plant them. Planted in the fall (probably early-mid September where you are) they'll start growing like crazy in early spring, and will present you with a whole bunch of garlic in mid summer. Harvest them then, stash them someplace cool and dry, and re-plant some for next year. Aside from the culinary values, it's probably THE most potent antibiotic herb around. It's another ingredient in my anti-infective soak.
Have fun!
summerthyme