This is a cool trick to give your tomato plants a head start. If you’re buying tomato sets, pick tall spindly ones. If you started yours indoors, they probably will be anyway.
For each plant, get a 2-liter soda bottle. Using a box knife or pruners, cut off the neck. (Tried skipping that step one year. Bad mistake.) Cut a vertical slit 3/4 of the way down one side. Cut two horizontal slits–across the top and bottom of the vertical slit. (So it looks like a capital H on it’s side.) Cut a notch in the middle of the vertical slit to make watering easier.
Lay the bottle on it’s side, slit side up, and fill halfway with potting soil.
Pull off the lower leaves, making your tomato plant look like a miniature palm tree. Lay the tomato plant on the soil, with the leafy part sticking out of the neck of the bottle. Fill the bottle with potting soil, and water well. Put in a sunny place and keep the soil moist. The buried part of the stem will grow roots. You can duct tape the slit shut. Just make sure you keep the notch open for watering.
What I like about this is that you can move the plants indoors at night, and out into direct sun during the day. Plus the dirt stays put.
When the weather turns warm enough to set out tomatoes in the garden, dig a deep hole, once again trimming the plant back into a palm tree, cut the bottle off the plant and lay the root ball in the hole. Fill the hole with soil or compost, right up to the bottom leaf, water well, and stand back.
My experience has been that you will see noticable growth within a couple of days. That giant rootball wants a big plant.