Commercial tomato growers have been using grafted tomato plants for years, and over the past two years grafted tomatoes have become more popular with home gardeners. Many nurseries now offer multiple varieties of grafted as well as non-grafted tomato plants.

Influenced by the coastal waters and mountains, summer in northwestern Washington is moderate and beautiful. Growing and ripening tasty tomatoes, however, can be a challenge.

In many Northwest gardens, tomatoes are grown in a hoop house or other protective structure.

Frequently there is little or no rotation of crops, increasing the chance of soil-borne diseases.

The use of more aggressive, disease resistant rootstock can protect the plant from environmental stresses, decrease the risk of disease and increase yield. ‘Maxifort,’ ‘Beaufort’ and ‘Colosus’ are three widely used rootstocks bred for disease resistance and plant vigor.

Experiments

In answer to the grafted vs. non-grafted tomato question, our 2012 experiment showed a definite difference. An ‘Early Girl’ grafted and an ‘Early Girl’ non-grafted were planted in the following three scenarios: (1) the open garden (2) a hoop-house like structure (3) in containers in a 4 foot by 4 foot by 6 foot clear vinyl structure next to the house. The soil mix, watering schedule and fertilizing schedule were the same for all plants.

Of these six ‘Early Girl’ tomato plants, the three on grafted rootstock were more resistant to disease and produced approximately twice as much fruit as the non-grafted plants. The grafted plants survived longer, withstanding the cooler nights of late season. This longevity likely contributed to the higher yield of fruit.

To say the grafted plants were more aggressive and grew to a larger size is an understatement. The standard 3-prong, 43-inch tall tomato cage made of 1/8-inch wire was inadequate, even when the grafted plant had been pruned.

Take advantage of the “industrial strength” cages that are 3 feet to 4.5 feet tall, made of 5/16-inch diameter wire available at nurseries and garden centers.

The ‘Early Girl’ grafted plants produced roots that were approximately 23 inches in length from the tomato stalk to the tip of the root, making the entire root span approximately 46 inches. Space grafted plants 4 feet apart, center-to-center so the roots have access to adequate nutrition and moisture.

In this backyard garden experiment the grafted plants inside of both protective structures produced ripe tomatoes earlier than all other ‘Early Girl’ plants (grafted and non-grafted).

The open-garden ‘Early Girl’ grafted was the winner in quantity of fruit produced, resilience to disease and longevity over all others in our experiment.

Do a comparison in your garden this year. Plant both grafted and non-grafted tomatoes of the same variety to see if you find a difference in fruit production, disease resistance and longevity of the plant. This could be the year when you have an abundance of luscious, homegrown tomatoes.

Watch for a tomato maintenance article in the Master Gardeners’ “Get It Growing” column in early July.

Judy English is a Washington State University-certified Clallam County Master Gardener.