Reasons a tomato plant might fail to bear fruit

I have tomato plants on an enclosed porch that have lots of blossoms but no tomatoes. They look like good healthy plants, growing very well; one is almost 5 feet tall. Am I doing something wrong? Help!

— Margaret

 

There are a couple of explanations I can think of. The first is simply a lack of maturity in the plant. As a tomato develops, it will usually bloom for a week or two or even three before starting to set fruit. Simply waiting will give the plant enough time to “get with the program” and start setting fruit.

The second reason would involve the space the plant’s growing in. An enclosed porch has two potential problems. The first is a lack of light. It may be bright in the porch but it will amaze you how much more light the plant gets out in the yard without a roof over its head. There’re lots of instances where the plant receives enough light to grow adequately, but it needs an extra level of light to successfully grow fruit.

The other problem is a lack of pollinators for your plants. Unlike most plants where the anthers (the male part of the flower that produces pollen) have pollen on the outside, the anthers of a tomato are a hollow tube with the pollen inside and it requires motion to shake the pollen loose from them. Though tomatoes can pollinize themselves, without that shaking, the pollen isn’t released and no fruit can be set.

Out in the garden, bees of various kinds do this as well as the movement from the wind. In an enclosed space like your porch, the bees are not able to forage through the flowers like they can outside and the plants are more protected from the wind. The best solution is to move the plants outside, if that’s possible. If it isn’t, then move them right next to the biggest expanse of windows or screens you can to maximize the light. You’ll also need to hand pollinize your plants. You can do this by carefully shaking the plants every day or two. The best way is to hold an electric toothbrush to the flowering stems so that the vibration is transferred to the flowers.

 

What sort of monster is supping on my old cherry tree now? The leaves at the tips of the branches are all curled up and sticky. I blasted the tree with Malathion last week, but the monsters must have ignored it. Please help.

— Sue

 

What you have is called black cherry aphid. Typically, people notice them in the spring when the leaves on their tree start curling. Inside are solid, sticky, gross masses of these insects. These little guys are pretty common around western Colorado on cherry trees in the spring. They’re not particularly harmful to the tree, but heavy infestations can stunt growth and occasionally dwarf fruit.

I think it’s late to spray to control these guys. The leaf-curling damage has been done, and it won’t be reversed by spraying. As we get into summer, the aphids will abandon the tree, and they’ll spend the summer on several different common weeds we have around here. In the fall, the winged adults will lay eggs on the twigs of the cherry tree to hatch next spring.

I think the best way to control them is to give your tree a dormant spray next spring just before the buds crack open. You’ll want to use a combination of a dormant spray oil and an insecticide like Malathion. Spraying now isn’t really going to change anything with the tree and besides, I’m sure there’s a lot of beneficial predatory insects like ladybugs and others there now munching away on the aphids and any spray you apply will kill them off. 

Dennis Hill is the nursery manager at Bookcliff Gardens, bookcliff
gardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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