Why aren't these tomato plants flowering?

While I've been downright smug about the bounty of my own tomato harvest, I have received a couple of plaintive cries from friends whose plants simply refuse to flower.

In both cases, the specimens concerned are being grown in restricted space - one lot in a grow bag in a sheltered sunny spot outside (pictured left), and the other in a pot on a sunny indoor windowsill. It's not a case of the blooms not being pollinated - neither sets have produced flowering trusses in the first place.

My own personal theory about this problem runs as follows. The plants are being spoiled: too much water or, more likely, too much fertiliser. Think about it: the flowering/fruiting mechanism is at itsmost basic a way for a plant to reproduce and ensure the next generation of plants. If the parent tomatoes are so cossetted they think they're going to live forever, there's no point in fruiting, right?

The "treat 'em mean, keep 'em keen" theory is one I subscribe to out of necessity as well as a desire to get a good crop. I can't get to the allotment on a daily basis and rarely feed my tomatoes, which are planted in soil, although the earth has been enhanced with home produced compoost and green manures. I also begin stripping the plants of leaves from the bottom as they begin to curl. This is a habit I must have picked up along the way - possibly from the TV show Gardeners' World, but I don't really know why I do it - perhaps it has the effect of shocking the plant into action.

Have I got it utterly wrong - is there some other obvious reason staring me in the face? I should also say that the outdoor tomatoes came from Heritage Seed Library seeds, while the indoor tomatoes were seedlings I raised and passed on. I wondered whether there were any other reasons why an indoor plant (on a windowsill in south London, not in a greenhouse) wouldn't flower - I can obviously see why pollination might be problematic unless it was by a constantly open window that provides access to lots of flying insects.

Comments

[Carol]

I agree with you. Too much fertilizer, especially nitrogen, just lulls the plant into a state of contentment and vegetative growth. They need to feel a bit of stress to put out some blooms to ensure the next generation before they die off. Keep 'em mean!

[Jess]

Spider mite? Almost anything grown indoors in a hot sheltered corner or room, especially a conservatory – and especially during the July we just had – is likely to get it. Someone who's never seen it before might not recognise it.

[Simon]

I was the south London windowsill plant owner (it has now left to live in a garden) and it seems to me that the problem was maintaining suitable moisture levels in the pot. Too little and the soil quickly dried, leaving the leaves to dry and curl. If I gave the plant enough to make the soil moist it would soon dry out again. It grew big and was healthy, there were just no flowers (or spider mites).

Incidentally, I am growing a basil and peppermint under the same circumstances and they are big, leafy and flowering so it might just be the plant. I'm going to try again next year to see if keeping the pot out of direct sunlight (below the windowsill) makes a difference.

[Simon]

I think I need to clarify the above description of my tomato raising techniques - the more water I gave it, the more leaves and stalks it grew. However, it just dried up if I tried to cut the water down. Perhaps it needed to be somewhere less sunny.

[STEVE]

Hi Jane, with regards to the Tomato plants not flowering there could be a couple of reasons for this, I have listed them as follows,

Copper deficiency:

Stunted root and shoot growth, blue-green curled, flabby leaves, few or no flowers. Manure is an easy cure; copper salts can be used with great caution (in too high a quantity, they can kill plants.) Bordeaux mixture applied at fungicidal rates will work.

Too much nitrogen:

Rapid growth, with many bright, light green leaves; poor flowering and fruiting. Stop fertilizing immediately with N, add P and K. Tomato fertiliser would encourage flower and fruit production.
I hope that these help you to discover the problem, regards Steve.

[josephine Davies]

HI, i have planted tomatoes indoors and the plants are huge but showing no sign of flowering. I think i have fertilised them too much. I am about to put them outside- how do I get them to flower

[Heather]

I haven't fertilised my tomato plants at all but still no flowers. Suddenly my strawberries are flowering. It seems all my plants are delayed from their nature fruit producing season.

[Taipo]

One of the things that tomatoes need is lots of light. 16 to 18 hours a day. This tells the plant that its summer and its veggying time. tomatoes use the change in hours of light and temporature to signal them they are in fall/autumn so shortening the hours to say 12 hours of daylight only will help trigger the flowering phase including all the tips given above.

[gloria simms]

I WAS TOLD WHEN A TOMATO PLANTS START TO FLOWER YOU ARE SUPPOSE TO CUT OR PINCH THEM OFF,IS THIS CORRECT?I ALREADY HAVE A DOZEN OR SO LITTLE YELLOW FLOWERS IN BLOOM,PLZ TELL ME QUICK.TK U

[Janene]

I have several tomato plants that sprouted in the old compost that I used to grow last years tomatoes in. I presume this is because tomatoes fell off last year and seeds landed in the compost. I have nurtured the plants into healthy tall plants, but have no flowers at all. Can anyone tell me if they will produce any flowers or fruit this year. They were in the greenhouse but are now out?ide to see if this will help.

[flatland petey]

currently i am growing cherry tomatoes that were taken as clones from my outdoor plants. i have them under a 250w hps about 10 inches away. i use botonicares pure blend pro line of nutrience on a cycle of 2 waterings of ph 5.9 balanced water for every 1 nutrient feedeing. i water them every other day. my indoor tomatoes are the same size as my outdoor ones even thou they were taken a month and a half after the original ones were started. i have just started flowering the indoor ones 3 days ago and they are already covered in flowers.

[james]

I have tomato plants growing in a green house with lots of sun I never used any fertilizer and they are big but not flowering at all. I then started ferilizing them and there still is nothing. any suggestions?

[ann marie]

I have to tomato plants right next to each other in a raised bed, one a 'husky' cherry tomato and the other something else, and the husky guy is putting out tons of tomatoes and the other just has 3 or 4 flowers. The 3-4 flower guy started his life in a pot and was very unhealthy; now he's growing like crazy, but hardly any flowers. The result of an unhappy childhood? But it seems that stress should have been good for him?

[pat miller]

my tomatoes are green and small a few red ones developed, but are rotting from the bottom

[s.v.kotbagi]

I am from hyderabad india. I have planted some tomatoes in pots in a sunny sitout. they are flowering and fruiting. I wish to know whether there will be many spells of flowering and fruiting in a lifecycle of the plant.

s.v.k

[miguel Llorens]

i have a ring of 3 tomatos plants 8' feet high but no blooms i have tried to clip the tops but they get bushier still no blooms and yes they are spoiled thank you :-)..cant wait till i can make me a square tomato so it will go from corner to corner of my square toasted bread..

[Marie Gell]

I am one of those "do it yourself "tomato gardeners.I have found that this year everyone is having a lot of problems with tomatoes because of the low night temps and high day temps, just too erratic. Also tomato planting dates were later this year because of cold rain and just too early too plant.This didn't help the watering regiment.Take into consideration the lack of bees for pollination( a small fan will help). All of these things can cause STRESS to the plant (and gardener).RECIPE for tomato Stress/Calcium Deficiency/or Blossom end rot:
Boil 1gal. Water and 15 ml(1 Tablsp)lemon juice, Add6 Tablsp.Bonemeal to water...Stir well. Cover 30 min.to help disolve. COOL. If not completly dissolved it's ok. Feed each plant 1 quart (1 ltr)of the solution at the roots and leaves (not over the plant). Repeat second time in 3-5 days.

[Marie Gell]

Gloria, Please do not pinch off the yellow flowers on tomato plants,those flowers will be the tomato. Each group of flowers is called a truss,some people don,t want their plants too high so they pinch off the growing tip of the plant after 4 trusses to stop it growing higher.Also after watering a plant, poke around the plant to see how far the water has gone into the earth or poke a stick down to the bottom of the root and leave it there for a few min. When you take it out of the dirt feel and look to see if the stick is wet ,dry, or moist. This tells you if the plant needs more water or less.

[Marie Gell]

Rule of thumb for fertilising for tomatoes;Use fertiliser with HIGH MIDDLE number,ie 10/15/10 or 4/10/4. (this is just an example.)Use Half the amount of the fertilizer (the instructions say on the container with the same amount of water) when the plant is green and the full amount of the fertiliser with the same amount of water when the plant is in blossom.Try watering your plants same time every day for better results. Irregular watering causes many,many problems. Poke a stick into the soil down to the roots and leave a few min. then take out and feel the stick and look to see if it is wet,dry or moist to guide you in watering the plants.

[Nick D'Agosto]

Ok, all of the above is very interesting. We have tried unsuccessfully to grow tomatoes in CT. Seemed like we would get a few at most in September. This year we resorted to an earth box and followed the recommended directions. Plants are very health, but no flowers. I've pulled off the "suckers" from the bottom as my deceased brother-in-law told me the low branches don't yield fruit, only suck the nutrients for fruit growth from the plant, hence the name. Any suggestions unique to earth box growing?

[Don Nichols]

true, tomatoes do need more P less N and if they have lots of dark green leaves no blossoms then cut the water down and add liquid P in some form of fertilizer... or just addd some good composted manure.