When temperatures are low and condensation or humidity is high, plants are at their most vulnerable to disease. Tomato plants with yellow leaves are common at this time of the season because of low temperatures and high demand for nutrients.
Watering
It’s good to reduce the amount of water plants receive when temperatures are low. Water in the morning to help avoid plants standing in cold wet soil overnight.
Feeding
Foliar feeding is also best done when air humidity is at its lowest – when air is damp, leaves will not absorb or release as much moisture as when the air is dry.
Translocation and Yellow Leaves
Tomato plants are amazing!
If they need more nutrients than they can absorb through their roots, they’ll take them from their lower leaves.
It’s a bit like borrowing from Peter to pay Paul – with Peter at the bottom and Paul at the top – the growing tip always gets the best portions.
Yellow leaves
You can buy the best quality potting compost or grow bags, but unless temperatures are reasonable, both day and night, plants will often display nutrient deficiencies in their lower leaves.
This is because nutrients are only available to plant roots above certain temperatures. So when it’s too cold, the only nutrients that are available to the growing tip(s) are those in the lower leaves.
Humidity plays its part too
Another point to make is that transpiration is reduced in wet weather – when humidity is high – so the uptake of moisture and nutrients from the soil is reduced.
Leaf removal
The lowest leaf branches can be removed. This helps prevent nutrient deficient leaves from becoming infected and passing that infection to the rest of the plant.
Yellow leaves are usually harmless but you may see all sorts of marks and many shapes and colours appear on lower leaves at this time of the season.
The best way to proceed is to remove the affected leaf branches. If the overall look of the leaves is lighter than your other tomato plants a foliar spray with a “pick-me-up” may be applied, such as:
- Liquid seaweed extract – contains a good range of nutrients.
- A general feed like Miracle Grow that contains micro nutrients.
- Magnesium (Epsom Salts) – will help make light green leaves a darker green.
- Calcium nitrate (from Chempak) contains nitrogen and calcium for strong healthy growth – also good for avoiding blossom end rot.
All of the above are best given as a foliar feed in order to avoid creating an imbalance in the soil.
When less is more
One of the most important lessons I’ve learned over the years I’ve been growing tomatoes is: it’s better to grow three plants well than six plants badly.
In other words, three well grown plants are able to produce more tomatoes, and of better quality, than six poorly grown plants.
Looking around my polytunnel I see plants that were sown early but given a lot of attention and are now doing very well. Plants that were sown at the right time but were left in their small pots for too long and therefore their recent growth has been slower than average. Some plants have a nutrient deficiency and some have a touch of fungal disease but mild enough to deal with.
When the remedy becomes the problem
It’s a strange thing that over feeding plants can cause nutrient deficiency …. why? Because when young roots are damaged by over feeding they are subsequently unable to absorb nutrients properly.
The same is true of watering. When young plants are over watered and soil remains saturated for days, if they don’t develop a disease that restricts both nutrient and water uptake, their root growth will be minimal and on a hot day they may wilt because a poor root system can’t absorb water quickly enough.
Identifying the root cause!
It can sometimes be very difficult to identify the source of a problem when plants have been over fed and over watered. Nutrient deficient leaves and wilting plants can be the result of too much rather than too little.
Tomato Plants and Aspirin
It has been suggested for a number of seasons that the active ingredient in aspirin triggers the immune system in plants and helps them protect themselves against some diseases.
Having read a recent article in which scientists have carried out tests that show this to be so, it seems a good idea to spray once a fortnight to be on the safe side. The recommended dose is around 75 to 100 mg per litre.
You can view the article here.
I read in the comments of one website that if you get a headache you should take two cherry tomatoes and if symptoms persist, consult your local gardener!
Slugs and Snails
Along with the recent wet spell, there seems to be an awful lot of slugs and snails around at the moment. If anyone has a creative idea of how to stop them (other than slug pellets) please leave a comment below.
Regards,
Nick
Grow bags
An advantage grow bags have over large pots is their large surface area – this allows extra access for the roots to air at the soil surface.
Grow pots (ring culture) are also helpful and keep excess water away from the stem base but allow water/food (aka fertigation) to be given at the fine roots in the inner ring nearest the stem.
Precaution
Most of us would love to be totally organic, but a spray with an anti-fungal treatment such as Bordeaux Mixture (copper sulphate) may be the only way to get a crop of tomatoes growing outside in a poor, wet summer.
Amy
Just wanted to thank you for the great article. My tomatoes in hanging baskets have developed yellow lower leaves and I tried everything to correct it with no success. Now that I’ve read your article I realize I can pinpoint the start of the yellowing to right when the weather changed and got suddenly colder. Thanks so much for the heartening advice!
David Sewell
With snails, share them with the birds but also give them some of the outside lettuce leaves to purge their system then scoff them yourself. Utterly delicious as an escargot stew or just with garlic butter; several million Frenchies can’t be wrong! Slugs can also be eaten but they are more chewy.
Renee’
Thank you so much for this site. I have been a gardener for many years. I am having problems with my tomato plants for the first time in many years. Leggy, yellowing, they are a lime green color and now turning almost white. I am thinking Nutrient block but, maybe not? It is affecting the Amish paste, Mortgage lifter’s and the prudence. Any ideas for me? I am still in the starter room so they are all in 4 inch pots.
Nick
Hi Renee, you may find that as the days grow longer and more light is available, the plants will improve.
There may also be an issue with the soil you are using – the nutrient balance could be wrong or there could be very little feed in the soil at all.
Rhys Jaggar
I had a go last night with a combination of buried beer in a cup and slug pellets around a bed of 5 maincrop potatoes that the slugs/snails had been munching on.
Although barely any slugs ended up in the beer, I picked off about 16 slugs/snails from the area where the slug pellets were spread and drowned the ones without shells and stamped on the ones with.
Along with other places I put traps down, I eliminated about 30 of the pests this morning. The swine were eating the radish, nibbling a courgette leaf amongst other things.
I guess I need to eliminate about another 30 a day for a month to get the problem under control!!
Nick
Hi Rhys,
Sounds just like my garden – I’ve lost a few seedlings lately, so they are now enemy number one!
Nick
Mac McCormick
Nick,
An interesting article regarding the use of Asprin to protect against some diseases, do you know if traces of Asprin remain in the fruit? The reason for the qustion is that I am prescibed an anti-coagulant and as Asprin is also used as an anti-coagulant would I be unwittingly exceeding the recommended dosage of anti-coagulants.
Nick
Hi Mac,
I wouldn’t be able to answer that question – I can only guess that the amount in the fruit would be extremely low and not interfere with your normal program. The best thing to do is to ask your chemist.
Nick
Rhys Jaggar
Nick
This Permaculture article has a good discussion about ways to control slugs.
http://www.permaculture.co.uk/articles/20-ways-control-slugs-permaculture-garden-or-allotment
Rhys Jaggar
Nick
I saw an interesting comment in the RHS ‘Garden’ monthly magazine which said that one reason for leggy tomato plants could be ‘temperatures warmer than 16C’, presumably at the time when the plants are still young.
Have you ever found this to be the case – I have three plants that went leggy last week in 15cm pots – they seem to be doing fine and producing new trusses at a great rate of knots – but if 16C is optimal for younger plants then maybe I should be putting plants out of doors sooner!!
Nick
Hi Rhys,
In my experience there are three ways to reduce legginess in seedlings and young plants.
Reduce temperature, reduce moisture in the growing medium or do as the hydroponic growers and give them 18 hours of light each day – artificial light of course in the spring.
Ideally, if we sowed in the middle of summer we would have no problem with legginess as there would be plenty of light – we would need very quick growing plants though!
Nick
Ross
Hi Nick
I also use beer to control the slugs. I re-use the disposable plastic cups from the water dispensing machine at work by burying a cup in the soil with about 1cm showing, then I drop another cup on top with the beer in it. Then when I need to dispose of the slugs I just lift out & bin the top cup that has the slugs in it then replace this cup with another one with fresh beer. This way its quick and easy to replace several cups without having to re-bury them each time.
P.S Don’t waste good real ale on them, just use the cheapo budget supermarket stuff as the slugs don’t seem to mind.
Nick
Hi Ross,
That’s good advice – I like the double cup idea!
Nick
Jack
I read this in the Mail online which is an interesting insight into the (very) common garden snail!
http://www.dailymail.co.uk/news/article-2637973/Bran-flakes-beer-ANYTHING-stop-slugs-Suddenly-slimy-blighters-How-fight-back.html
Jack
Nick
Thanks Jack – I give it a read!
[email protected]
hi all,i’ve found a few tips to at least keep slugs and snails off plants.one is to use copper tape around pots or copper wire.its said to give them a small electric shock with static electricity.another is if you have any bramble cuttings to lay a ring of them down where you want to protect,young ones are best as they have more spikes and the slugs dont like to be spiked.not tried any of these methods but may be worth a try.
Nick
Hi Andy, If it’s not too expensive, running it around the base of the polytunnel may be work a try.
Nick
alex mothersill
I have for the past few years used nemaslug an have not had much problem with slugs,( do not like slug pellets having pets and loads of visiting wild birds) I also use it in my composter.
Seems to work still get the odd one but days are gone when a row of seedlings or transplants disappear overnight
Happy growing Alex
Nick
Hi Alex, I’ve seen nemaslug advertised for some time but have never tried it – maybe now’s a good time.
Nick
Bob Iles
Hi Nick, I seem to recall that some time last season you mentioned some small hooks that clip into the greenhouse glazing rails, so far I have been unable to locate any, any help would be much appreciated. Regards Bob.
Nick
Hi Bob, Were the clips for holding the glass panes in position or for supporting the plants?
Bob Iles
Hi Nick, the hooks were for supporting plants.
Nick
Hi Bob, you can get them here … https://www.tomatogrowing.co.uk/newsletter/yoyo-plant-supports
Cheers, Nick
Rhys Jaggar
The old wives’ tale about slugs is to put one of your plastic cups in the soil filled to just below soil level with beer – apparently the slugs will drown in the stuff after being attracted by the smell.
I’ve not tried it yet, but like you, we have masses of slugs this year – they’ve been caught half way up broad bean plants, attached to lettuce leaves and have munched their way through at least 4 newly transplanted lettuces (which teaches me I need to invest in cloches this autumn).
Nick
Hi Rhys,
I’ve been reluctant to share my real ale with anyone but I guess the time has come!
Nick
Buster
Hi Nick. In my experience beer traps work & so does damp bread as a lure. Perhaps snails & slugs have a keen sense of smell! Maybe it’s a yeast thing!
Personal choice how you dispose though. And the waste of beer.
Thanks for the site.
Buster
Nick
Hi Buster, I think I’ll go for the damp bread option and drink the beer myself!
Cheers,
Nick
Valerie
Good Morning Nick.I too am plagued by slugs and snails.Last year I used coffee grounds and egg shells.
I am told that sand helps to protect and of course the night time ramble round the garden!
Don’t throw the collection over the fence.They will come back! And don’t try to drown them unless it is in a closed container full of water.Personally Why I just squash them and leave them for the birds!
Nick
Hi Valerie,
Good morning to you too! I like the idea of a night time ramble round the garden – I’m a bit squeamish when it comes to squashing so I might introduce them to a drop of beer followed by the outdoor rubbish bin – if I can stop them escaping!
Nick