Background to tomatillos

Tomatillos (Physalis philadelphica) are related to tomatoes and are native to Central America. They are thought to have been domesticated by the Aztecs over 2000 years ago. Although they have been exported to many countries, they are most often associated with Mexico where they are either eaten raw or cooked and made into salsa. They are closely related to the cape gooseberry (Physalis peruviana) which is yellow and has a sweeter taste.

The plants are grown in a similar way to tomatoes, but are generally more vigorous and less particular about planting conditions.

Tomatillos produce fruits the size of a cherry tomato, surrounded by a characteristic papery husk. They are harvested when they have filled out their papery case, and are still green and have a tangy flavour. They are quite tart when raw, but take on a citrus flavour when cooked.

Growth of plants

Experimenters grew in a range of locations scattered around the UK ranging from Weymouth to near Oban. 58% of participants grew them outside and 42% in a glasshouse or polytunnel.

On average people’s tomatillos emerged 12 days after they sowed them, with a range of 5 to 34 days. The average date for first flowering was the 21st June, and first fruits set, on average a month later on the 19th July. Surprisingly, in this sample of people, growing inside did not significantly advance flowering or fruit set.

A few people noted that young plants suffered from odema, visible as numerous little pinprick bumps on the leaves. We also experienced this when raising plants at Ryton Gardens. This is a physiological disorder which occurs when the plant takes up water at a faster rate than it can evaporate from the leaves. We found that the condition went away when we watered very sparingly for a week.

People’s general comments about the plant were that, despite being termed a ‘bush’ plant, its growth was quite indeterminate, leading to unruly and untidy growth. There were few problems with pests and diseases, slugs being the most common. A few people experienced red spider mite, but nobody reported blight. Many people found the plants ‘unruly’ to grow.

Yields

Only 61% of people managed to produce a yield from this crop. The reasons for failure could not be pinpointed to a common cause but included poor germination and early plant growth and a cool summer resulting in crops growing slowly and never fruiting.

Tomatillos were quite late producing a harvest with the average start date for harvesting 21 August. The earliest was 20th July. Average yield was 0.6 kg per plant, but the highest yield was 6.8 kg per plant.

Yields were not significantly increased by growing inside, and there were no consistent trends associated with the latitude they were grown at. However, it is worth noting that one of the highest yields of just over 2 kg per plant was produced outside, as far north as Kendal.

Some individuals produced prolific yields, and complained that they did not know what to do with all the produce. Advice would be that 5 plants are too many for most families, and 2 plants would be sufficient. It is necessary to grow more than one plant as they are not self-pollinating. Some achieved very high yields and didn’t know what to do with all the produce.

Eating qualities

Opinions were divided on the flavour of raw tomatillos. There was an almost equal split between people that said they were quite unpleasant (33%), neutral (28%) and quite pleasant (26%) with the remainder stating they were either very unpleasant (8%) or very pleasant (5%). The opinion improved markedly once they were cooked with 70% of people rating them as either quite pleasant or very pleasant.

In terms of flavour qualities, the most common flavours commonly associated with the raw tomatillos were tangy (59%), sour (41%) and bitter (39%). Once they were cooked, these bitter flavours were reduced and only 8% of participants said they tasted bitter. At Ryton, we found the time of harvest important. The unripe tomatillos had a pleasant tangy flavour, but if they were allowed to ripen too much, this became cloyingly unpleasant.

Most people found that tomatillos had a tangy taste and preferred them when cooked.

Making them into salsa was the most popular way of eating them, and most people enjoyed the recipe provided. They were also frequently used to impart a tangy taste to chutneys and Indian and Mexican dishes.

The Verdict

Only 35% of participants said they were ‘quite likely to’ or ‘would definitely grow them again’ and 28% said they would definitely not grow them. Failing to get a crop put many people off, but conversely, some were put off by the glut of produce that they had little use for. Those that enjoyed growing them found them productive, easy to grow and troubled by fewer pests and diseases than tomatoes. They wouldn’t be considered a replacement for tomatoes, but could be useful for replacing lemons or limes in recipes that require a tangy taste.