Do tomatoes stay green at the base of the stem even though they have long since ripened? Then green collar struck in the final cultivation stage. We explain what it is, why the damage is harmless and how to avoid it.
What causes green collar on tomatoes and how can you prevent it?
Green collar on tomatoes is caused by excessive sunlight, excess nitrogen fertilizer, lack of potassium and magnesium supply and excessive watering. As a preventative measure, you can provide shading, fertilize and thin out sparingly and keep the pH of the soil above 6.
Multiple causes – an unmistakable symptom
Green collar overtakes the home-grown tomatoes during the season finale. The fruits do not take on the desired color all around. Instead, a green or yellow collar with hardened pulp is revealed. Since this damage has existed for as long as tomatoes have been planted, the causes are well known:
- too intense sunlight combined with heat build-up
- excessive thinning and cutting back
- Overdose of nitrogen-based fertilizer
- excessive watering with subsequent waterlogging
- unbalanced fertilization combined with potassium and magnesium deficiency
So green collar has no chance with tomatoes
If the dilemma has occurred, there are currently no treatment options available. In advance, informed hobby gardeners still have the best chance of protecting tomatoes from green collar. Pay attention to the following aspects of care:
- Provide shade during hot midday hours in summer
- ignore the south wall of the house as a location
- measured and cut cautiously
- do not allow the soil pH to fall below 6
- avoid nitrogen-based fertilization in favor of potassium and magnesium
- Prefer light fruit varieties, such as 'Culina', 'Dolce Vita' or 'Vitella'
Experience has shown that the fruits in the outer part of the plant are more often affected by green collar. Denser foliage in this region provides natural sun protection without plunging the fruit into Egyptian darkness.
Are infected fruits still edible?
If ripe tomatoes have a green collar, the toxic solanine has still dissolved. The fruits can therefore be harvested and consumed without hesitation. However, green collar causes hardening of the pulp in the narrower area of the stem base. It is therefore recommended to cut out these areas with a knife.
Tips & Tricks
Experienced hobby gardeners avoid tomato deficiency symptoms by consistently fertilizing with nettle manure. This traditional fertilizer is easy to make yourself in the garden. An undesirable oversupply of nitrogen and the associated risk of green collars is also naturally prevented.
Find out more about blossom end rot.