As you can see from the picture above some of our beefsteak tomato plants suffered leaves turning white this year. And yes, I did do everything right. Almost.
From experience I can tell you that white tomato leaves are most often caused by over exposure to direct sunlight and wind or problems with nutrition and soil quality.
Tomato leaves turning white has happened to me before. First time it happened I simply did not harden the tomato plants before moving them outdoors. I started my tomato plants indoors and then moved the seedlings to a greenhouse. I assumed that was enough. It was not.
But this time was different.
In this article I will share how to avoid tomato leaves going white as well as explain how to fix the problem should it happen. I will end the article by explaining where it went wrong for me this year.
How to avoid white leaves on tomato seedlings and plants
Get the following 5 things right and you have come a long way to minimize the risk of tomato leaves turning white.
1. Harden tomato seedlings before transplanting outdoors
The generally accepted rule tells us that we can move our tomato plants outdoors when the minimum temperature is above 10 degrees Celsius (50 degrees Fahrenheit).
Still, regardless of temperature, you need to harden your tomato seedlings before moving them outdoors.
The process of hardening a tomato plant is simply put to gradually expose the seedling to its new growing environment outdoors.
And this must be a gradual process as environmental factors like direct sun and exposure to wind are most likely completely new to your tomato seedlings.
Start by placing the tomato seedling or plants outdoors for a couple of hours on a cloudy day. Choose a spot that is protected from wind and make sure there is no chance of direct sun.
Gradually increase the time spent outdoors and introduce direct sunlight carefully.
The whole hardening process should take at least a week to ensure that your plants get accustomed to direct sun exposure.
2. Choose location wisely
Even when your tomato plants are properly hardened it is absolutely critical to choose your location wisely. And this is even more true if you are transplanting younger tomato plants or tomato seedlings outdoors.
Think full sun with minimum exposure to wind. But do make sure your tomato plants are not overly exposed to direct sunlight during the hottest part of the day.
If you grow tomatoes in grow bags or pots, you will of course be able to move your plants if needed. Still, this would often be after the fact when at least some damage had already been done. And to be honest, large pots and grow bags are not always that easy to move around the garden- especially when the tomato plants are mature and large.
3. Be patient
For most gardeners space becomes an issue as tomato plants mature and grow tall. I go through this process every year with my tomato plants. I am waiting for that day when my tomato plants can be transplanted into the garden – permanently.
Sure, it works to keep smaller varieties like cherry tomato plants indoors for a few more weeks than expected. But beefsteak tomatoes will quickly grow to more than 1,5 meter (5 feet) tall and with many tomato plants space quickly becomes an issue.
Still, you need to wait for the temperature and overall weather conditions to be favourable before moving your plants outdoors. You are looking for a stretch of calm weather with light to moderate rainfall with a minimum temperature above 10 degrees Celsius (50 degrees Fahrenheit).
Being patient will go a long way to help protect your plants avoiding that levees turn white.
4. Go easy with the fertilizer
More nutrients is not the solution to all problems. In fact, too many nutrients or the wrong type of nutrient can actually do more harm than good.
Young tomato seedlings do not need nutrients. Start giving your tomato plants half the recommended dosage a week or so after transplanting your tomatoes to bigger pots.
Use a nitrogen based fertilizer when the plant is growing and developing leaves, stems and branches. Switch to a phosphorus based fertiliser when the plant starts to flower and develop fruits.
5. Pot or grow bag size holding enough soil
Tomato plants grow big and the roots need space to grow as well as breathe. If the roots are too restricted leaves will loose their vigour, start yellowing and even turn white.
So what is then the best tomato plant pot size? I use the following minimums for our tomatoes.
|Tomato variety||Minimum recommended size|
|Cherry tomatoes (determinate)||20 litres (5 US gallons, 4.4 Imperial gallons)|
|Beefsteak tomatoes (indeterminate)||27 litres (7 US gallons, 6 Imperial gallons)|
The above recommendations work for us but remember to look at your plants to see how they are doing. Do you have leaves that turn white? Maybe tomato leaf curl or even yellowing leaves?
After all, each tomato plant is unique and these are all signs that you need to take action.
2-step method to understand and fix white leaves on tomato plant
As I have developed hands on experience from tomato leaves going white, I will share my two step method on how to fix this problem with tomato leaves turning white.
There are too many lists that include everything as a possible cause. And sometimes too much information makes it hard to take action and to know what to do.
I have found these two steps to be sufficient to save my tomato plants when suffering from white leaves.
1. Identify most likely reason for white leaves on tomato plants
Sun scald is by far the most common reason why tomato leaves turn white. And your first step analysing anything happening to your plants should always be to ask this one question:
Are there any recent changes in growing conditions or environment that could affect the plant?
Changes could be obvious like the recent transplant of your tomato plants outdoors. But it could also be less direct like the move of an indoor plant that was previously giving partial shade to your tomatoes during the hottest part of the day.
And whereas tomatoes want full sun, plants may need some protection from the most intense sunlight during the hotter parts of the day.
Solution when tomato leaves turn white due to sun scald
Whether the plant is growing indoors or in your garden, you need to move the plant to a more protected and suitable spot.
Next, assess the damage to the affected areas. If only individual leaves, go ahead and remove the leaves. Do not remove entire branches unless all leaves are beyond rescue.
Consider companion planting to provide shade and wind cover to be able to use the original spot later in the season.
2. Problems with nutrition or poor soil quality
If I know my plants are unaffected by sun and wind, I move on to looking at nutrition and soil quality.
Solution to poor soil and lack of nutrition
If there are no changes in exposure to sun light, wind or growing conditions in general, I assume there is an issue with nutrition or soil quality. I say assume as there is no way to know for sure.
First I repot tomato plants into a larger pot with fresh soil that drains well. I plant the stem deeper to help the rot system grow strong. Next, I sit back and observe. After one week, I add half the recommended dosage of fertilizer as needed.
Growing tips when starting your own tomato plants from seed
Do not start your tomato plants too early in the year. Plant your tomato seeds about 6-8 weeks before the expected last frost.
When starting seeds too early it is common to run into space issues. In a worst-case scenario, you have to move your plants outdoors too soon risking white leaves and losing plants.
Remember to harden your plants before transplanting your tomatoes outdoors. You are looking for calm weather conditions and a minimum temperature above 10 degrees Celsius / 50 degrees Fahrenheit.
Other possible causes of leaves turning white
1. Fungal disease
Most tomato growers are sooner or later faced with fungal diseases and pests like aphids, leaf miners, and thrips. And tomato plant disease is another of many possible causes of leaves turning white.
How to protect against disease and pests
We use a DIY Neem oil spray solution to protect against diseases and pests. Apply the solution at dusk or dawn to minimize the risk of affecting beneficial insects and pollinators.
Neem oil is completely organic and works really well against both pests ad diseases if available in your area.
2. Too much fertilizer
Giving tomato plants too much fertilizer can also cause tomato leaves to turn white and even kill your tomato plant.
Tomato plants need nitrogen-based fertilizers during the early growing stage when the plants develop green leaves, stems, and branches.
As the plant matures and enters the flowering and fruit stage, we switch to a phosphorous-based fertilizer to help the tomato plant bloom and develop fruits.
But giving too much fertilizer will have the opposite effect and tomato leaves turning white is a signal you should take seriously. Especially if there are no changes to growing conditions.
How to avoid giving too much fertilizer
Always start by giving half the recommended dosage to avoid the risk of tomato leaves turning white due to too much fertilizer. Now observe your tomato plant and increase as needed.
What to do when too much fertilizer has been given
It is easy to give more fertilizer when needed, but more complicated to take away fertilizer already given.
Tomato plants with leaves turning white due to over-fertilization need to be re-potted and given fresh new soil.
3. Make sure it is caused by a lack of nutrition
Leaves losing their strong, vibrant green color and turning yellow, brown or white can be a sign of lack of nutrition.
But it does depend on several factors. Your plants could also suffer from overwatering, soil that is compact and does not drain well or simply from lack of light.
Before giving more nutrition look at the plant and rule out any other possible causes
- Well-draining or compact soil?
- Only happening to leaves on the bottom part of the plant?
- Just leaves on one side of the plant?
- How old is the plant?
- Roots sat in wet soil leading to root rot?
And then, and only then give your plant half the recommended dosage and observe the effect.
So why did my tomato plant leaves go white?
This year was different. I did harden my plants for about two weeks. Still several of my beefsteak tomato plants had several leaves go white, silver and then shrivel and die.
I was caught by surprise by a weather pattern where we would have hot weather with full sun one day to be followed by heavy winds and rain the next day.
Temperatures may have dipped below 10 degrees Celsius (50 Fahrenheit). And needless to say, I do not know the actual minimum temperature taking the wind chill factor into account.
The good news is that my beefsteak tomato plants were strong enough to survive. But I did lose some flower-producing branches and I will have a smaller harvest from these 9 plants.
But luckily, it was only 9 plants.