I grow tomatoes in cages it saves garden space plus plants produce several times more tomatoes, better than letting plants grow all over the place on the ground. July 1st all my plants are 6' tall and loaded with about 35 lbs of ripe tomatoes each. In the past I have noticed only the new plant growth produces tomatoes. Aug 1st plants will have grown over the top of the cage and down to the ground plants are technically 12' feet tall now but only the top 6 ft are producing tomatoes. Sept 1st plants have grown across the ground 6' plants are technically 18' tall now and still the top 6 ft of the plant is producing 95% of the tomatoes. 18 tomato plants are taking over the whole garden. Last year I did 2 experiments, one was cut plants off at 6' tall and the other was grow new plants to take the place of old plants. Plants that are trimmed off so it is only 6' tall take a month for the plant to make new growth then all the tomatoes are on the new growth. I lost a month of tomato harvest by trimming the plants. Planting new tomato plants from seeds every 3 weeks keeps the harvest going but new plants take up extra garden space. 3 squash plants died in June and I harvested my green beans in July that is where I planted tomato plants from seeds. As it turned out new replacement tomato plants worked better than trimming the tomato plants. I harvested about 50 lbs of green tomatoes about November 12 the day before frost killed all the plants. Green tomatoes slowly got ripe in the kitchen we ate the last 4 tomatoes on Christmas day.