[OakR]

As per the title really. Last year I watered my tomato plants every 3 or so days but this year lately I've hardly watered them (and it has rained a bit) - last time I watered them was about 1.5 weeks ago I think. The plants seem to be coping just fine and we've more water forecast for the next few days (in London) so at this rate I might be going 3 weeks without watering them unless it really warms up.

Previously I'd water even though the plants looked ok, but am wondering if I should just wait til they don't and then just start again?

The weather is so strange this year not really sure what to do - maybe I'll try half this way and half the normal way.

[mumofstig]

Don't water unless there's been no recent rain.
When you think they might actually be dry - it's worth making a small hole with a trowel to see if the soil is damp 3 or 4 inches under the surface, if it is there is no need to water.
Waste of water if they don't need it and you'll be diluting their taste.

[OakR]

Thanks - do you always test the soil or do you sometimes go by how the plant looks? I'll do the soil test as you suggest but wondering whether to experiment with some and water them much less (even if it looks dry post test) to see how they get on. I have a few of the same varieties to can compare (not a scientific test of course).

I also have most of my tomatoes on a new plot I took on this year that seems to be even more clay based than my last one, and has apparently not had any manure or compost added to it for 4 years or so. I'm wondering if deeper down it's holding the water more than my other plot.

[mumofstig]

I don't always, but I've been in this place for years and know the soil, but if I'm really not sure I'll test. The soil was bone dry down to about 12ins, at one stage earlier this year 
It's always a question of judgement, but if the plants do start to wilt, you risk them dropping flowers or fruit - so I always err on the side of caution.

[mrs bouquet]

Does this apply if growing in a tomato grow-bag ?   Mrs Bouquet

[JayG]

The aim should always be to keep the soil moisture as constant as possible whether growing inside or out, in soil or compost - blossom end rot is mostly caused by inconsistent watering, as well as the problems mum has already mentioned.

Whatever your watering regime, try not to wet the leaves when doing so - obviously natural rainfall does exactly that, but it makes sense to do what you can to minimise the chances of blight taking hold at this time of year.

[mumofstig]

Does this apply if growing in a tomato grow-bag ?   Mrs Bouquet

The advice was specific for tomatoes grown outside in the soil

[jambop]

The aim should always be to keep the soil moisture as constant as possible whether growing inside or out, in soil or compost - blossom end rot is mostly caused by inconsistent watering, as well as the problems mum has already mentioned.

Whatever your watering regime, try not to wet the leaves when doing so - obviously natural rainfall does exactly that, but it makes sense to do what you can to minimise the chances of blight taking hold at this time of year.

Depends on what you regard as being the right moisture level in the first place? I grow only outside and I water my tomatoes from time to time if it has been dry. I know people who will never water their tomatoes after the initial water when planting out nor they will not feed their tomatoes. They believe that if you water you end up with a blob of water and not much taste. I agree to an extent I watered fairly regularly when it was dry last year and the tomatoes, especially the beef toms, while large were lacking flavour We are about a week into a hot dry spell which is going to go on for another 14 days at least and shade temps of 30C go out into the sun... it goes up a notch and the heat is stifling. I am watering most things really heavily but not the tomatoes they get 2.3 L per plant every week or so. This is the start of summer it will get hotter still but we will get the odd really heavy rain shower to give the soil as respite.

[JayG]

Tomatoes no doubt find life easier growing in southern France than they do in the UK, which is why they often need more TLC here.

[jambop]

Tomatoes no doubt find life easier growing in southern France than they do in the UK, which is why they often need more TLC here.

I think they do prefer the warmer temps but still find it strange that some are very reluctant to water their tomato plants when there are long very warm spells. For example the temperature at mid afternoon will be around 30C for the next 14 days and the lowest night temperature is going to be about 20C . I am not sure that tomatoes actually like it too warm but they do like it to be a consistent temperature... probably closer to 20C than 30C .

[AnneB]

I only water outside tomatoes in very dry conditions.  I do give then a weekly feed of comfrey tea. I find they taste better than indoor tomatoes. Worth a go especially with blight resistant types.

[Subversive_plot]

I'm with JayG on the idea of providing consistent water.

Our weather in summer tends to include periods of too much rain, with periods of too little rain in between.  If left to go "natural", fruit developed under dry conditions will tend to crack open as the fruit suddenly swells with water.  Such tomatoes are unsightly and prone to rot. 

I find that blossom end rot has more to do with whether the plant had enough calcium, rather than watering regime.  But, that is just my experience.

[jambop]

Blossom end rot is a thing I have never had a problem with in all the time I have been growing tomatoes down here. Even though it get quite hot and we do get long spells without much rain... I even grow a variety, san Marzano, that I have heard many on here say is prone to it and never had any problems at all. I think it is most probably linked to some element which the soil is lacking which causes the problem.

[JayG]

This is the RHS's take on blossom end rot:

https://www.rhs.org.uk/advice/profile?pid=395

I've found different varieties, grown in the same greenhouse in the same compost, have different susceptibilities to BER - had problems with Marmande until I took much greater care with the watering, but don't think I've ever seen it on Gardeners' Delight (having smaller fruits no doubt helps.)

Also agree with Subversive_Plot that irregular watering can make fruits split - again, some more prone than others (Sungold particularly so in my experience.)

[New shoot]

I've found different varieties, grown in the same greenhouse in the same compost, have different susceptibilities to BER

I have found the same with greenhouse tomatoes.  I don’t think I have ever had it on outdoor ones, but my soil is clay based, so it takes a long time to dry right out.

I water the outdoor ones when they first go in, then only if it is really dry.  I haven’t watered them for a few weeks now.

Tomatoes are very susceptible to dilution of flavour if you do water too much.  You have only got to taste basic supermarket salad toms to know that. I did watch a cooking show once where the presenter came across tomato vines growing curled up in circles on the ground. They were high up on a hillside somewhere hot and arid and the farmer never watered.  He explained that the tiny cherry sized fruits were the sweetest possible because the vines struggled so much.  The presenter was in rhapsodises over them, but there were only a few on very miserable looking plants