Thanks, Kim, for the confirmation. I checked on Chinese chives, it's the same as garlic chives mentioned in Field Roebuck's book. He stated, "In at least one controlled experiment, when planted underneath roses, garlic chives completely eliminated spider mites and reduced aphids." Rose magazine site stated that high-nitrogen chemical fertilizer does encourage aphids. The Canadian website that advocated fall fertilization, rather than spring, cited less insect problems with earlier nitrogen fertilization for wheat fields. Garlic chives have white flowers, it is listed among the invasive species. In my experience with invasive species, it's the least invasive, since it can be pulled up easily. It's a tiny bulb - rather than invasive roots. If you cut the flowering stem off before it becomes seeded, then you stop the growth. I was hoping it becomes invasive enough to gather a gallon for making pot stickers -but it did not spread fast enough in our 40" inch annual rain and high germination in magnesium rich soil. I also have the American chives with purple flowers, this is invasive since it spreads by roots. This chives is more drought-tolerant than Garlic, or Chinese chives. Calendula, or potted marigold, is just as pretty but more drought-tolerant than regular marigold. Calendula host many beneficial insects, especially green lacewings. These lacewings fly around and eat Calendula's pollens. But they give birth to larvae, named aphid lion. More info: "Each lacewing larva will devour 200 or more pests or pest eggs a week ... After this stage, the larvae pupate by spinning a cocoon with silken thread... the adult will live about four to six weeks...Each adult female may deposit more than 200 eggs. Nectar, pollen, and honeydew stimulate their reproductive process." What I like the most about garlic chives, or Chinese chives is its medicinal and anti-inflammation properties. It's especially yummy in potstickers, better than green onions. I like Calendula (comes in bright yellow and bright orange), since they are drought tolerant and still bloom during frost. Below is a picture of Calendula in my tomato garden:

I keep pulling up the starts from that *^%*@+#&!@% tree all over my yard...front yard, side yard and back yard, and the tree isn't even in my yard! I got so sick of it's crap coming over my side of the fence that I cut a monster sized limb out of the tree this past Fall. Didn't want to risk a run-in with the #)%*()#^@! neighbor by using my gasoline powered pruning attachment, so I attacked it with my saw blade attachment on my 16 ft long pruning pole. Never have I had so much satisfaction with a saw before. Really worked out my frustration on that tree. Cut it in the most un-arborly fashion in hopes of killing the entire tree, but I doubt it will suffer that badly. Next I'm considering drilling a hole through the fence and into the tree and attaching a direct feed from a bottle of Round-Up, the really concentrated woody vine and brush killer kind. Yes, I'm that insane. Oh, and about the red bloated tick looking bugs that come with this tree...TonyK was right, you can't kill them with anything but soapy water and it has to be almost waterless soapy water or else they just keep on going. UGH!!!!!!!

I dont know if this is an issue in the UK, but here in Western Australia - what you are describing is generally caused by water repellent soil. Dusty sandy soil can prevent water from penetrating roots and deprive the plant of nutrients and water - even if you are flooding your plant. put a few drops of water into the soil. if it beads up then that is your problem. The solution is simple. buy a wetting agent and add a small amount every few months or so - via a watering can or spraying it. wetting agent is nothing more than a detergent which breaks down the surface tension of the water. You can use household dishwashing liquid but I dont recommend it for regular use as unlike commercially prepared wetting agent - dishwashing detergent will change the PH of your soil. Adding considerable organic content into your soil is also a good solution.

Mint likes full sun and some heat, or if in an area that is very hot, morning sun and partial afternoon shade. Soil should be consistently damp but not too wet. High humidity or a lot of rain can lead to the leaves developing powdery mildew. In my area it is not advised to plant in the ground because it is horribly invasive and hard to control, and makes for awkward conversations with your neighbors when mint runners spread under your driveway and colonize their garden. Your climate may be too humid and cool for it to really take off (you might do a little research into which varieties do better in your area), but then again I've had new plants sulk through their first summer and then come back with a vengeance the following spring. So you never know.