Not only do tomatoes and potatoes rhyme, they have other things in common as well. They are from the same family of plants, both are warm-season crops, and both have toxic leaves and vines. Their growing requirements are similar as well. The good news is if you can grow one the odds are you can easily grow the other. The bad news is that both are susceptible to the same kind of blight, so if one gets it the other will, too.
Dig the area 2 feet deep and 3 feet wide for each tomato and potato plant. Add in a bucket of compost to the bottom of each hole. Mix equal parts compost and the removed soil. Add in slow-release fertilizer per package directions. Refill the holes for the tomato plants.
Remove the lower leaves from the stem of the tomato seedling until only the top four to six remain. Plant the tomato seedling so that the stem is completely buried with only the leaves showing at the top. The stem will throw out roots, making the plant stronger.
Refill the holes for the potato plants to within 12 inches of the top. Place two seed potatoes in the bottom of the hole a few inches apart. Cover with 2 inches of the compost and dirt mixture.
Water the plants well so the ground is thoroughly saturated. Feed with a well-balanced fertilizer every month. Both potatoes and tomatoes do best with regular watering. Drying out the ground leads to stress for both; tomatoes become prone to fruit cracking with inconsistent watering.
Remove any blossoms from the tomato plant until it is 18 inches high.
Add soil to the hole of the potato plant as it grows. When the plant reaches the top of the hole, continue to mound up soil around the stem. Potatoes grow the edible part of the plant, the tuber, in the area underground between the stem and the roots. Covering the stem with dirt as it grows means more potatoes.
Cage or support the tomato plants with trellises.
Harvest the tomatoes as they ripen. Most tomatoes are red, so when they turn a deep red color it means they're ready. Tomatoes of other colors such as pink, yellow, chocolate, white and orange should be tasted to see if they're ripe. If the flavor is that tart and sweet tomato flavor, make a note of the color and harvest when the remaining tomatoes turn that color.
Harvest potatoes at any size. The tiny potatoes cook quickly. The longer the potatoes are left with the plant the bigger they will grow until the leaves start to yellow. When that happens dig all the potatoes out.