Vincas dying, nothing growing!

I am in Houston, TX in a new home (built about a year ago). Since moving in we have two flower beds in the front yard both which we built up slightly last fall with soil and mulched. Both beds get mostly full sun except in the morning. One bed is doing fairly well, a pygmy date palm is growing well and the purple fountain grass is doing pretty well (a hibiscus, bird of paradise and agapanthus are doing well). The other bed is not faring so well! A hibiscus, bird of paradise and some dwarf agapanthus are doing fine, but the pygmy date palm won't grow, the purple fountain grass has just a few fronds of new growth and is tiny.

Most concerning though is that no annuals I plant will grow- in early spring the petunias died, then the begonias and now the vincas are on their way out. The soil is mostly clay and I'm not sure how well it drains. We've stopped watering at all, as I thought we were over doing it. So now we're going to start up again maybe once a week if needed. Here's a picture of one of my sad vincas! I haven't tried anything new yet, as I don't know where to start! The other bed has slightly less yellowing of the vincas. Where do I start here?

Thanks,
Allison

You'll get lots of advice on this. I just happened to see your post early on. You can rule out the heat as the cause of the problem w/the vincas. The yellowing, unless it's from too much water, means they're hungry. It could be an iron deficiency or need for nitrogen or both. I wouldn't worry about trace elements. Is your soil friable, or does it still have the consistency of clay- hard when dry, malleable when wet? Wet some and squeeze it with your hand. If it crumbles, that's good. If it stays in one mass and simply makes ribbons between your fingers, that's bad. In that case you need to work more organic matter into it. A&M is now recommending a couple of inches of expanded shale for clay beds also. It works kinda like sand or perlite but won't wash away or settle out like sand does. It allows air and water to penetrate.

You may have to raise your beds a few inches if water is standing. Your area can get heavy rains at times. I lived there nearly 30 years.

If you have clay soil, the only fertilizer you need is a slow-release nitrogen fertilizer. A soil test by A&M is the best thing to do. They give you instructions when you get the kit at your county extension office. I would definitely get the soil test because since you just bought the house you don't know if any toxic material was dumped where these beds are. A soil test would settle that question.

When you watered did the water just sit on the top or did it drain away? How much soil did you add on top? I dealt with clay at our old house and it takes a lot of digging it out and years(yes I said years) of ammending it till it's just right. You may want to wait and fix the soil first before you do any more planting...(you can do containers).
If you have full sun there you have to be real careful with what you plant. Begonias are a shade plant so that's why they didn't survive.
According to plant files the date palm is a slow grower.

Is it possible there is some type of pesticide or herbicide in the ground? It doesn't look like a nutrient deficiency to me, since the veins are yellowing first. It looks like the plant is taking up something harmful from the ground. I think DP has the best advice: Get your soil tested.

We have about 4 inches of friable soil, then it's hard clay below that. The water doesn't seem to pool when we water the bed. I'm going to collect soil samples as suggested and send them in. I found the form and was wondering if I need to do all 3 types of testing- Routine(pH, NO3-, P, K, Ca, Mg, Na, S, and Conductivity), Micro (Zn, Fe, Cu, and Mn) and Organic Matter?

If your having it done might as well do it all.

While you are waiting on a soil test, try mounding up some of that 4 inches of 'friable' dirt into a raised bed, maybe just a small section as a test area. Pick up another 6 pack of vinca from the nursery and plant in that area as a comparison to what you have now. I am thinking that the clay hardpan under your beds is your problem. If you could break that stuff up down to about 10 to 12 inches, it would improve drainage a lot. The surface of a clay soil can form an almost impermeable layer that prevents water penetration. Breaking it up down deep every couple of years prevents that.