Oval-shaped plum tomatoes have thick flesh and less pulp than regular tomatoes, which makes them ideal for sauces and canning. Less prone to oozing when cut, plum tomatoes can also be eaten fresh. Plant plum tomatoes from transplants, or begin seeds indoors six weeks before the final frost date in your region.
Starting Plum Tomato Seeds
Fill a seed tray with seed starting mix. Then poke a 1/4-inch-deep hole in each chamber of the tray using a pencil.
Drop one tomato seed in each hole and cover it up with the seed starting mix. Water the seeds until the seed starting mix becomes saturated. Place the cover on the tray to keep the moisture in. Plum tomato seeds germinate within a week.
Move the seeds to a sunny south-facing window once the seeds germinate, and remove the cover from the seed tray. Check the moisture level daily; seeds will die if they dry out. Continue to nurture the tomato seeds until they have two sets of scalloped-edged leaves.
Fill 4-inch pots with potting mix. Poke one long hole in each pot with a pencil.
Stick a fork in the chamber of the seed tray. Pull up with the fork and grasp the seedling at the base. The seedling will come free. Place it in the hole in the pot, burying the entire seedling except for the leaves. Plant all seedlings in this manner and continue to water the seedling whenever the soil becomes dry.
Wait until the temperature outdoors reaches 55 F both day and night. Then prepare the ground to grow your plum tomatoes. To prepare the tomatoes for planting, move them outdoors for several hours a day when the weather warms. Over two weeks increase the length of time until the tomatoes are outside all day.
Growing Plum Tomatoes
Prepare a hole for each plum tomato plant that's wide enough for the length of the tomato plant and several inches deep. Plant tomatoes in a full-sun location in the ground.
Grasp the tomato seedling at the base and gently pull it from the container, whether you're planting your seed-grown tomatoes or plum tomato starts. Dig a hole deep and wide enough to accommodate the root ball. If the plant is in a peat pot, make sure the entire pot is under the soil, so the peat material does not wick water away from the plum tomato. Leave 18 to 24 inches between plants.
If your plant is tall and spindly, North Carolina State University Extension recommends using the trench planting method. Remove all but the top cluster of leaves and place the tomato start in the hole horizontally, bury all but the top third of the plant under 2 to 3 inches of soil. Roots will develop along the length of the stem, making for a stronger plant.
Water the newly planted tomatoes thoroughly. Place a tomato cage around each plant to support the plum tomatoes as they grow.
Continue to water tomatoes whenever the soil becomes dry to the touch, watering until the soil is saturated. Depending on the variety, plum tomatoes ripen in 55 to 80 days.