This past winter I was reading my gardening books and searching the internet for ideas on growing vegetables near each other that may be beneficial to each other. I came across several references saying roses and tomatoes make good companions in the garden. This sounded interesting so I looked closer to learn how these two plants may benefit each other.

Both have many of the same cultural requirements. Both grow best in full sun and slightly acidic nutrient-rich soil, and both do best with consistently moist but not wet soil. My research suggested that the benefit to roses was that tomatoes potentially can protect roses against black spot. There is some evidence that the alkaloid solanine in tomatoes prevents the fungus that causes black spot. Solanine is a toxic alkaloid that also has pesticidal properties found in plants in the nightshade family. I could find nothing in the literature stating that roses have any benefit to tomatoes.

Both tomatoes and roses can be susceptible to verticillium wilt which is a fungus that stays in soil where diseased vegetables or other diseased plants were previously grown. Today most rose rootstock is R. multiflora which is resistant. To be safe plant tomatoes that are resistant to the fungus.

Finding no other warning I decided to plant a tomato in the Rose Garden. Since we use no chemicals to control black spot or insects Fred Klatz and I decided this would be a good experiment. The Home Garden was experimenting with several methods of growing tomatoes and had two Early Girl plants left that were past their prime but still had potential. Space was found among the roses that would provide sufficient room for the plants to grow without crowding the rose bushes. Holes were dug deep enough to leave only the top leaves uncovered. No fertilizer was added and none was applied during the summer. A drip line was put around each plant and connected to the drip irrigation system in the Rose Garden. A tall tomato cage was installed over each plant. Both the roses and the tomato plants received water twice a week for 45 minutes throughout the summer starting in mid-June.

By early July we noticed that the tomato plants were thriving, had set fruit and were getting quite tall and bushy. The rose bushes all looked good and showed almost no signs of black spot. We did not prune any leaves or vines from the tomato plants. By late August the tomatoes were 6 ft. tall completely hid the cages, and loaded with ripening tomatoes. We then stopped watering the tomatoes. None of the Master Gardeners we talk to had ever seen their tomatoes grow this well. One Master Gardener said he has been growing Early Girl tomatoes for 20 years and has never seen anything like these tomatoes.

On September 11 we evaluated and tasted tomatoes both in the Rose Garden and in the Home Garden. We did not observe any of the tomatoes in the Rose Garden to have cracking or blossom end rot and all the ripe tomatoes were a consistent size for the variety. Many of the tomatoes in the Home Garden trials showed signs of cracking and blossom end rot. The skin of the Rose Garden tomatoes was less tough than those in the Home Garden. The tomatoes grown in straw as a dry land crop in the Home Garden were somewhat sweeter in flavor. In a second taste test on September 23 rd two people thought the tomatoes in the Rose Garden were their favorite for flavor and texture. The others who participated felt those grown in straw had better flavor. We do not know what the yield was compared to those grown in the Home Garden since we were growing them for prevention of black spot on roses and never thought to harvest and weigh how many pounds of fruit they produced.

Do tomato plants have any other benefit to roses? In the spring we decided to remove the Fragrant Cloud bush this fall because it has never looked healthy, had produced few flowers each year, and always had black spot. This rose is an own-root rose planted in 2010. On October 2 nd we were in the Rose Garden checking the bushes for black spot and other disease and noticed this rose. Not only did it not show any sign of black spot but had grown much taller (at least double what it was in July), had many new canes and most of the canes had flower buds. Now we do not plan to remove Fragrant Cloud. We have no other explanation for the sudden change in this rose so maybe this is another benefit how tomato plants are beneficial to roses.