Tomato Plant Not Flowering? Nitrogen Age plus Light
A tomato plant not flowering is often getting too much nitrogen, too little direct sun or soil that is still cold. University of Georgia Extension notes a tall dark green plant with heavy growth plus no blooms points to excess nitrogen. Check the feeding routine, count hours of sun plus note soil temperature.
The short answer
Look at the plant first. Tall dark green growth with no blooms points to excess nitrogen. Thin growth in shade points to low light, since University of Arizona Cooperative Extension notes tomato plants need at least 6 hours of full sun. Stop high nitrogen feeding plus give the plant more sun.
How does nitrogen affect tomato flowering?
University of Arizona Cooperative Extension notes too much nitrogen increases vine growth at the expense of fruit for 3 to 4 weeks after feeding. Once the plant uses the nitrogen, flowers plus fruit set should follow. University of Georgia Extension notes too much liquid feed can cause heavy growth plus hinder flowering.
| Factor | Guideline | Source |
|---|---|---|
| Direct sun | At least 6 hours | University of Arizona Cooperative Extension |
| Soil temperature | 60F or warmer | University of Georgia Extension |
| Soil pH | 6.0 to 6.8 | University of Georgia Extension |
| Bloom range | Drops below 55F or above 95F | University of Maryland Extension |
| Excess nitrogen | Vines grow for 3 to 4 weeks | University of Arizona Cooperative Extension |
Source: University of Arizona Cooperative Extension, University of Georgia Extension plus University of Maryland Extension.
How much sun do tomatoes need to bloom?
University of Arizona Cooperative Extension notes tomato plants need at least 6 hours of full sun a day. University of Maryland Extension lists excessive shade among the causes of poor blossom set plus advises adequate sunlight, water plus nutrients. Iowa State University Extension notes low light under trees can also stunt plants.
How do cold soil plus early season weather affect blooms?
University of Georgia Extension notes tomatoes have problems in soil colder than 60F, plus phosphorus is less available below that. University of Maryland Extension notes tomato flower production drops below 55F plus low spring temperatures can deform the first fruit cluster. Plants set out early may wait for warmer weather.
How to: step by step
- Count the hours of direct sun on the plant.
- Note when the plant was set out plus how warm the soil was.
- Stop high nitrogen fertilizer.
- Resume feeding only once small fruit appear.
- Shift containers to a sunnier spot.
- Water deeply once a week in dry weather.
Troubleshooting
Huge dark green plant with no flowers: excess nitrogen. Pause feeding until blooms appear.
Thin plant in shade: low light. Move containers to full sun.
Young plant in cold soil with no buds: cold conditions. Give it warmer weather.
For related reading see the effects of environmental stresses on weed plants, reading fertilizer numbers plus soil checks for cannabis. Kind Seed Co also stocks cannabis seeds.
Sources
- Troubleshooting cultural problems in tomatoes (C1089), University of Georgia Extension
- Tomato challenges, University of Arizona Cooperative Extension
- Poor blossom and fruit set of vegetables, University of Maryland Extension
- Managing tomato diseases, disorders, and pests, Iowa State University Extension and Outreach
FAQ
Do tomatoes need special fertilizer to flower?
No. University of Arizona Cooperative Extension notes the brand of fertilizer is not important plus advises high phosphorus with moderate nitrogen at planting. It advises no more feeding until flowers plus fruit set. University of Georgia Extension notes the second feeding should wait until pollination plus small fruit appear.
Can heat stop tomatoes from flowering?
Yes. University of Maryland Extension notes plants often stop producing blossoms in midsummer heat plus resume in late summer or early fall. Tomato flower production drops above 95F. Iowa State University Extension notes high day plus night temperatures reduce flower production, so fewer fruit form during hot weather.
Should I prune leaves to get flowers?
Heavy pruning does not help. University of Arizona Cooperative Extension lists too much pruning among the causes of blossom drop. Iowa State University Extension advises avoiding heavy pruning or shoot removal, since fruit suddenly exposed to sun can scald. Leaves feed the plant that makes the flowers.
How many hours of sun do tomatoes need?
At least 6 hours of full sun a day, per University of Arizona Cooperative Extension. University of Maryland Extension notes excessive shade is one cause of poor blossom plus fruit set. A spot that gets sun from morning through early afternoon gives plants a good chance to flower.
Does afternoon shade help tomatoes bloom?
In hot weather it can. University of Maryland Extension notes placing pepper plus tomato plants where they get late afternoon shade can improve yields over the season. It also notes wetting foliage during hot dry periods can reduce heat stress plus encourage flower plus fruit set. Morning sun still matters.
