How to Grow Thompson Seedless Grapes Indoors

Prepare large, heavy, 15- to 20-gallon pots and containers for Thompson seedless grapevines. Use heavy clay pots with drainage holes for balance and drainage. Allot one pot to each grapevine.

Set your pots in their permanent locations before planting. Put them in sites with bright all-day natural or artificial light and good air movement. Keep them away from heat sources, which dry the soil and foliage. Put them against walls if possible for use in trellising the plants.

Mix a potting soil of 1 part topsoil or garden loam, 1 part peat moss and 1 part organic compost. Fill each pot three-quarters full of this mixture. Grapevines need rich, moist, loose and quick-draining soil for root formation and long-term growth.

Plant the Thompson seedless grapevines one per pot in holes as deep and twice as wide as their root systems. Spread the roots in the holes for best root-to-soil contact and fill the holes slowly with potting mix. Grapevines cannot grow with air pockets around their roots.

Water each grapevine with 1/2 gallon of water settling the soil around the roots. Prune each grapevine down to three growing buds. Put a trellis behind the pots supporting the grapevines as they grow.

Put the grapevines on a schedule of 2 inches of water every four to five days. Indoor grapevines dry more quickly than outdoor grapevines and may need more frequent waterings to maintain soil moisture. Lay 1 inch of organic mulch over the soil in each pot for decorative and practical effect.

Fertilize the Thompson seedless grapevines the week after you plant with 10-10-10 fertilizer. Mix the fertilizer into the soil around the grapevines, with at least 6 inches of space between the two, and water. Fertilize again every spring, but never get fertilizer granules on the foliage.