Tomatoes: Best Practices for a Terrific Harvest

What could be better than the taste of a fresh, ripe, warm tomato, picked minutes earlier from your own backyard? This week, Susie Everding, Master Gardener in Training, discusses some of her growing, maintenance and care tips that may help you achieve your best tomato harvest ever.

Planting and Mulching

You have nurtured your tomato plants from seed or purchased seedlings, prepared your garden beds, checked planting dates for your area, and set out your crop. Once they are in the ground, Susie suggests giving them a great start by putting mulch such as straw or grass clippings around your plants.

Mulched Tomatoes. Image credit: Susie Everding

As regular participants in this series will know, mulching has many benefits:

  • retaining moisture in the soil
  • moderating soil temperature
  • adding nutrients back into the garden via decomposition
  • minimizing erosion
  • protecting plants from splashes of soil onto the lower leaves, thereby reducing the risk of disease


There are two types of tomatoes – determinate or indeterminate. Determinate tomatoes (e.g. Green Zebra or Principe Borghese) grow to a fixed size and produce their fruit at roughly the same time. Because of this growth habit, these bush varieties do not need pruning or suckering and can be supported in a tomato cage.

Indeterminate or “vining” tomatoes, the most common type grown by home gardeners, will continue to grow until stopped by frost. Under the right conditions some varieties can reach 10 feet in height and will need to be supported. Susie stakes her plants with rebar, posts which are inexpensively available at most hardware stores, and ties the plants with soft fabric such as pantyhose. Avoid rigid ties or thin string, which can cut into the stems. Indeterminate varieties will need to be pruned.

Image credit: Susie Everding


Tomatoes need a consistent water supply, which in most years is not supplied by rain alone. Typically 1-2 inches of water are needed per week for garden tomatoes (those in containers will require more). It is best to water in the morning rather than at night and to direct water to the roots, not the leaves. A soaker hose works well for this purpose. 


Indeterminate tomatoes are pruned since their enthusiastic growth inhibits light and air from reaching all parts of the plant. Susie prunes to just one or two main stems and removes the 3 lowest shoots, which helps lessen the spread of disease pathogens splashing up from the soil to the leaves. 

The majority of growth in a tomato comes from suckers, which are shoots arising where the main stems and branches meet (the axils). If left to grow, they will produce flowers and fruit, as well as more suckers! While the yield potential is high with an unpruned plant, it is easier to support, manage and harvest an indeterminate tomato when it has been judiciously pruned. Suckers can be pinched off at their base by hand, or clipped out with (disinfected) secateurs.

Tomato sucker. Image Credit: Susie Everding

Fun Fact: Did you know that you can propagate suckers? Choose healthy shoots, and place in a jar of room temperature water. They root easily and within a few weeks you will have a tomato plant, cloned from the original, ready for planting.


With the warmth of August summer days, tomatoes gradually ripen and are ready for picking and eating or preserving.  While tomatoes are often left to ripen on the vine, they can also be harvested at the “breaker” stage, when they have reached 50% of their eventual ripe colour. Simply leave them on the counter for a few days to fully ripen with no loss of flavour or nutrients. 

There are some advantages to this early harvest, since it avoids potential damage to crops resulting from a heavy rain (leading to ripe fruit splitting), or from wildlife that enjoys a tomato as much as we do.

Diseases, pests and hygiene

Tomatoes are prone to several bacterial and fungal diseases, but there are best practices that can mitigate the risk of infection.  First, plant tomatoes in full sun, far enough apart to allow for good air circulation around the plant, and for sunlight to penetrate through the foliage. Planting at least 18 inches apart (if pruning to one main stem) and up to 3 feet apart (if two or more stems are intended) is recommended

Practice crop rotation. Avoid planting crops in the tomato family (including potatoes, peppers and eggplants) in the same beds for at least 3 years. This allows time for soil-borne pathogens to diminish and for soil nutrients to be replenished.

If diseased leaves appear, clip these off and dispose of them. Unlike commercial composting operations, home compost piles rarely reach temperatures sufficient to kill plant pathogens, therefore discard diseased plant material in the green bin. Don’t neglect sanitizing your tools to avoid transfer of diseases from one area of the garden to another.

Blossom End Rot

Blossom End Rot. Image credit: Anna Sadura Healey

This physiological condition affects the blossom end of the tomato fruit and manifests as a brown spot which gradually expands and darkens. It is caused by an insufficient amount of calcium reaching the fruit. Interestingly, this is rarely due to a calcium deficiency in the soil itself. Calcium is transported into the plant via water movement, and thus dry conditions and  inconsistent watering are at the root of this issue.

From time to time you may note that the blossom scars are abnormally large with crevasses or holes at the end of the tomato. This is not a disease, but rather a condition called “cat facing”. It is thought to be caused by abnormal environmental conditions during flower development, such as when temperatures drop to less than 15C.

Tomato Hornworm

While there are various insect pests to contend with, Susie’s nemesis is the tomato hornworm. 

Tomato Hornworm. Image credit: The Old Farmer’s Almanac

This caterpillar is green, nicely camouflaged and can defoliate much of the plant in a short time. You may be able to detect it by the presence of its frass or droppings. If you see it, squish it or drop it into a bucket of soapy water. They also make great chicken food if you happen to have a flock!

While growing a successful tomato crop may require some effort, it is worth it, don’t you think?


Susie recommends the following book:

LeHoullier, Craig. Epic Tomatoes: How to Select & Grow the Best Varieties of All Time. North Adams, MA : Storey Publishing, 2014.

And, online resources about pests and diseases in tomatoes can be found at:

OMAFRA disease and pest identification

Cornell University, College of Agriculture and Life Sciences