From June onwards, the rhubarb plants develop flowers that look beautiful and the gardener could be delighted with their appearance. In reality, however, the rhubarb blossom is viewed with skepticism and is said to have an incompatible or toxic effect. Many gardeners let the poles grow all summer and stop harvesting as soon as the plants start to bloom. Here the question arises: Does the rhubarb season really end in June and what about the oxalic acid content?

Traditional harvest

The rhubarb season officially ends on St. John’s Day, June 24th. To date, it is not known whether this date is a traditional superstition based on the oxalic acid contained in the plants. The fact is that the plant receives new vitality through the break until the next season and sprouts strong stems in the coming spring. The consumption of stalks with a high content of oxalic acid is also avoided if the last harvest takes place on St. John’s Day and thus before the first flowering. Even after this period, the plant is not poisonous.

Location and care

Rhubarb plants only have low demands on the location. A damp and shady location strengthens the plant and ensures a rich harvest. Regular watering is necessary on dry days, which is preferably done in the morning or evening. Under no circumstances should the rhubarb plant be watered in the sun, otherwise the leaves will burn and deprive the stems of their strength. The easy-care plant thrives best if you choose a loose, nutrient-rich soil and apply a little bark mulch around the plant.

The oxalic acid

In high doses, oxalic acid can have undesirable side effects. The rhubarb is edible, but less digestible in the summer months than in spring. In April the plants contain the lowest amount of oxalic acid, as the content builds up in the vegetation phase and thus increases from month to month. The plant grows vigorously between April and the end of June, which is why rumors about the toxicity of the rhubarb flowers persist. The fact is that the flowers have no effect on the oxalic acid content of the plant. When the plant is in bloom, peeled and cooked, it can be eaten just as safely as it was before the flowering period. Note: A person weighing 60 kilograms would have to consume 36 kilograms of fresh rhubarb for the oxalic acid to have a noticeable effect.

Rhubarb – how to harvest

Rhubarb stalks are not cut above the ground, but slowly twisted out of the ground with their lower end. The break occurs at the thinnest point and allows the particularly tender and tasty roots to be consumed. To prevent brisk flowering, the first rhubarb flowers can be carefully removed. This has the advantage that the plant puts all of its strength into the shoots of the stems and thus grows vigorously and voluminously beyond the month of June. If the plant is allowed to bloom, it becomes weaker and weaker depending on the flowering frequency and ultimately only sprouts very thin stems.

Tips for tolerable enjoyment

The plant, which by the way is not a fruit, as is often wrongly assumed, should only be consumed in cooked and peeled form. Rhubarb plants are a vegetable that is very popular due to its sour flavor and is best eaten in sugar or with a vanilla sauce. To delay the flowering time or to prevent it completely, it is also possible to put the plants under a protective film in spring. Rhubarb stalks from a shady location taste more intense and are easier to digest than is the case with sun-drenched plants. Basically, however, rhubarb is not poisonous even when it blooms, but just more woody and less tasty than the spring harvest.

Cut in autumn?

There are just as many myths about the autumn pruning and wintering of rhubarb plants as about whether the stems are still edible after flowering. Rhubarb plants do not need to be pruned. When winter approaches, the plant pulls in its leaves on its own and the shoots die off. At the same time, they serve as fertilizer and protect the roots from the effects of cold when the first ground frost comes and the garden slowly moves into the winter period. Under no circumstances should rhubarb plants be touched with a knife. By pruning, the plant is unnecessarily damaged, which in turn affects the budding in spring and makes the plants weak.


Rhubarb flowers are not poisonous, which means that the stalks are edible even when they are in bloom. However, the plant wood after it blooms, which has an impact on digestibility and enjoyment. The easy-care plant loves a shady location and thrives best when the harvest is not done with a knife and you do not prune it in autumn.

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