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Rhubarb, Rheum rhabarbarum
Every May, the rumor spreads in private kitchen gardens that flowering rhubarb is poisonous and no longer edible. Numerous hobby gardeners believe the slogan and end the already short harvest season when the rhubarb blossom unfolds. Here you can update your knowledge of how flowers affect harvesting and edibility. You can find out here what the actual poison content of rhubarb is.
Oxalic acid interferes with enjoyment
Oxalic acid - troublemaker when enjoying carefree rhubarb
Since rhubarb has enriched the local menu with its fruity and sour taste, the topic of a possible poison content has been in the air. The focus is on oxalic acid, which is contained in the fruit vegetable in addition to vitamins and minerals.
The odorless and tasteless substance impairs the absorption of iron in the human body, attacks tooth enamel and binds calcium. These properties are of particular concern for children and kidney patients. However, oxalic acid only has serious effects on health in large quantities, as the following figures illustrate.
- Oxalic acid content in fresh rhubarb stalks: per 100 grams from 180 to 765 milligrams
- Toxic from a dose of 600 milligrams per kilogram of body weight
According to this, a child weighing 20 kilograms would have to consume a whopping 12 kilograms of fresh rhubarb stalks to be seriously harmed. For an adult weighing 60 kilograms and not suffering from kidney disease, the lethal amount is a staggering 36 kilograms of the fruit vegetable. The final all-clear on the toxic content is given by the fact that oxalic acid is found in its highest concentration in the skins of rhubarb. If the stems are peeled during preparation, the content is reduced to a minimum.
flowering time and oxalic acid
No correlation between flowering time and oxalic acid
There is a stubborn misconception among home gardeners that flowering rhubarb has such a high oxalic acid content that it is no longer edible. This misconception results from the fact that an unpleasant, bitter taste develops in numerous herbs at the beginning of the flowering period, which makes consumption impossible.
However, this process has no relevance for the flowers of a rhubarb plant. The fact is that flower and oxalic acid are not interrelated. You can safely harvest and eat the stalks while the plant is in bloom. However, there is a compelling reason to still remove the buds and every single flower. The following section explains why this is so.
remove flowers
Removing rhubarb blossoms has benefits
Rhubarb lovers need to hurry if they want to savor the invigorating fruiting vegetable's short harvest season. The time window for the sour pleasure has hardly opened in April when the end of the harvest season is already approaching in June. Even this short term is reduced as the creamy white flower spikes unfurl. During May and June, the plant invests all of its energy in dressing up for bees, bumblebees and other pollinators.
With its inflorescences, the fruit vegetable primarily pursues the goal of multiplying as numerously as possible. The growth of the fruity stalks takes a back seat. Experienced home gardeners remove the buds and blossoms so that the yield is not reduced prematurely.
That is how it goes:
- Do not cut the bud or flower with a knife or scissors
- instead grasp the base of the stem with your fingers
- turn clockwise and break out at the same time
As soon as the plant registers the absence of the rhubarb flower, it diverts its energy into growing fresh stalks. By sacrificing the opulent flower, you will be rewarded with a higher crop yield over a longer period of time.
Flower is edible
In the course of growth, the first buds and rhubarb flowers sprout early. Flower induction begins as soon as the plant has been exposed to temperatures below 10 degrees Celsius for 12 to 16 weeks. In our part of the world, it may be necessary to remove the blooms as early as mid/late April in order to optimize the harvest.
If you have broken a bud or flower, do not throw it in the compost. Hobby gardeners with a penchant for culinary experiments have discovered that flower buds are excellent as a spicy, sour vegetable side dish. Steamed in salt water and served with a cream sauce, rhubarb blossoms enrich the menu.
harvest time
St. John's Day marks the harvest time
Harvest season does not end when a rhubarb plant blooms. Traditionally, prudent house gardeners stop harvesting on St. John's Day, June 24th.
The following considerations speak in favor of observing this date:
- the growth spurt at the end of June is used for regeneration
- in the course of the summer, the oxalic acid content increases significantly
Every rhubarb contains the vitality for up to 10 years. In order to deliver a rich harvest every year over this long period of time, the plant must be allowed a phase of regeneration. For this reason, home gardeners no longer harvest rhubarb stalks from the end of June, especially since the oxalic acid content has reached a level that is no longer beneficial even for healthy adults. The only exception is in the first year of harvest. In order to protect the still young plant, the harvest time ends in May.