Because those greens are cool crops and at summer heat/humidity in zone 7 or higher they will not do well.
Do you like beans? plant some variety of those. Or wait until August and do fall planting that can last well into winter.

Kale, mustard etc. bolt quickly in high heat. Also, the pests attack greens without mercy as the temps go up. As for Swiss Chard... I grew it all through the summer last year in a self watering container. It worked great and I'm growing it in the Earthtainers again this year. I tried growing it in summer in our raised garden in previous years. If you keep it watered thoroughly and if you can give it some protection from afternoon sun (plant it near something taller that will filter some of the sun), you may be able to grow it. You'll have to keep an eye on it for pests that come with warm temps.

i'm growing swiss chard right now and it's doing fine. however, i never seem to get the right time for spinach. we have it in the ground now, for the 5th time, and it has already bolted within 6 weeks of planting and hardly any growth.

our arugula and other salad greens usually tend to do fine in summer, though.

Some of the problems growing greens in the summer is they don't germinate as well in extreme heat and can go to seed and become bitter.

There are some heat resistant varieties though. I grew "Salad Bowl" lettuce all summer long last year and it grew like crazy. I would trim a bunch off for a salad and a few days later it had already grown back. I'm trying Vates Collard Greens this year, it's supposed to be ok in the heat. Georgia Collard is another one that was recommended for growing in hot weather. As Opal mentioned you will have to keep it well watered though.

It's going to be fairly mild the next week or so, I would think they'd germinate easily if you get the seeds started soon.

Good luck,
Franny

Malabar spinach can take the heat of summer. Some people have found it to be invasive, though.

There are some really good suggestions here. Thanks folks.
I'll forego the mustards and turnips until Fall but I did plant some swiss chard today. I received some in a trade and thought I'd give it a try. I planted Fordhook and Rhubard chard. This is really exciting. I love experimenting in the garden.

The salad bowl lettuce sounds great Franny. Did you start seed in the cool of Spring? My lettuce simply will not germinate. I've given up trying eventhough I love it because there's nothing like the cool, crisp flavor of homegrown lettuce is there? I buy plants most times but it gets expensive.

I have planted my Swiss chards back in March and they are about 8" tall, not as big. I had planted lettuce mix same time but they have come and gone, with few bolted ones left.
This was my first try on SC and so far it seems that they are very slow to grow and nowhere near bolting. So then we sould cross out SC as cold crop I guess, althouhg they thrive in cold but don't mind heat either.

My neighbor had planted lettuce seed in late May and I was surprised to see it doing well so I thought I'd give it a try too. I started mine in June and it did great.

I used "Lettuce Bowl" seed by Ferry-Morse. I picked the seed up at either Home Depot or Lowes (I believe it was HD).

Here's exactly how I planted mine. I put a thin layer of Jiffy seed starter mix about an inch or so deep on top of my garden soil. Then sprinkled the seed over it. Then topped the seed with a VERY light layer of the seed starter mix. I kept it moist and within a few days it had germinated and it took off from there.

Hope this helps,
Franny

Found Salad Bowl at Lowe's today! The packet says slow bolting, good heat tolerance.

I grow many heat tolerant lettuces and greens. You need to look for Asian greens commonly grown in Thailand and parts of China and Japan that have similar climates to ours. Baker Creek and Evergreen Seeds have some great descriptions.

Try Jericho Lettuce. Here's a thread about it.

It is a loose head, Romaine type and will do even better with regular watering and some afternoon shade. It's the kind of thing you harvest the whole head of so it's good for succession planting.

Good Luck,
-Ron

In order to grow greens in the heat they need ground cover, shade and water every day.

feeding weekly or more often,which is something hard to get around to.

even then they can bolt dependent then upon there age.

I have some mustard and turnips. I'm eating them. Keep plenty of water on them and leave the grass for shade.