This spring I planted a Niagara grape and a Concord grape about 9 feet apart. Each is against a patio pillar. The soil is heavy clay, but I modified it a lot with topsoil and compost. The pillars/patio create the potential for each grapevine to grow up to 10 feet tall, and my husband is going to add trellis beams between the 2 pillars. I live in Central Texas.

Could I plant a third grapevine between the two I have? I know it's a bit close, but I could prune it so that its canes are much higher or lower than the canes of the other two, so they'd have more room to grow. We can add trellis anywhere we need.

The Niagara and Concord are both growing like gangbusters. They look great.

I know the answer may be no, but if not, feel free to recommend a variety.

Would it be alright to add one?