Summer Tomatoes: Prune Tomatoes Back or Start New Ones from Seed

Q. All the tomatoes are harvested.  What do I do with the vines? Trim them back for fall? Pull them up and buy new in the fall?  Your suggestions please.

Comment: in the hot desert we have two seasons of tomato production; spring production until July and late summer until the late fall. Here, desert tomatoes stop producing during the summer months until temperatures dropped back down to the 90s again and produce until late in the fall, usually mid December.

A. I will try to make a short video and some pictures to describe this. If your tomatoes look healthy, I would cut them back after you have finished picking the fruit. How you cut them back will determine how they will perform for the rest of the summer and into the fall. By leaving healthy tomato plants that we like intact and pruning them back we save a lot of time trying to reestablish new transplants or starting them from seed. Transplants are difficult to find this time of year. It makes more sense to start new plants from seed directly in the garden.

Pruning tomatoes. When you cut tomato plants back, always cut them to a strong side shoot. Be careful about cutting back the tops of the plants too drastically. If the plants were very bushy or if there is still fruit on the interior of the plant, cutting them back too hard can cause sunburn to the interior stems and any fruit remaining. Sunburn to the fruit will ruin them of course and sunburn to older stems will cause a lot of problems and the plants may die in our hot summers. When you cut the tops back, make sure their is enough leaf cover to shade the interior stems and of course the fruit as well. Cutting the tomato plant back at the sides is less damaging. Always make sure any cutting tools are sharp and sanitized. Fertilize the plants right after cutting them back.

Sunburn on tomato fruits

Learn a new word: imbibition. Now is an excellent time to start tomatoes from seed directly in the garden for a fall crop. Soak the seed in water-soaked paper towels overnight before you plant them. This is called pre-germination. Pre-germination helps bypass the first obstacle in seed germination and that is keeping the seed moist. If the seed is kept moist, the first stage in germination called imbibition can occur quickly.The biggest problem in planting seed this time of year is the soil drying out quickly and preventing imbibition or killing a young emerging seedling. Pre-germinating the seed, or making sure the seed has imbibed water, gives the seed a jumpstart.

See a seed imbibition video

Plant directly in the garden. Plant pre-germinated tomato seeds 1/4 inch below the surface of the soil or lay the seed on top of the soil and cover with a 1/4 inch layer of topsoil. Soak the area with water and cover the seeded area with a very light mulch of pine shavings, finely shredded newspaper, vermiculite or peat moss. This very light surface mulch will keep the soil moist between irrigations and encourage germination without suffocating the seedlings. Shredded newspaper is probably the most problematic of the group. Soil temperatures are great for germination during the summer months if the soil is lightly shaded with a mulch. Once they have germinated and produced their first set of true leaves, you can move them to a new location and pamper them.