June vs. August Rhubarb: Does the Season Affect Color and Flavor?

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 Good morning, everyone. It is the middle of summer, and I hope you are all doing well.

Here, I have been weeding the rows in the vegetable garden. There seem to be relatively few weeds because of the large leaves of the rhubarb, but the plants appear to be wilted and not very vigorous because of the heat.

And the most distinctive feature was that there were very few of the characteristic red petioles that symbolize red rhubarb, with most of them being lush green.

The red color of these petioles comes from anthocyanin, a type of natural pigment produced by plants. Rhubarb petioles contain various types of polyphenols produced by the plant. Among them, anthocyanin is one of the representative pigments responsible for red and reddish-purple coloration.

Simply put, polyphenols are a group of compounds found in plants, and flavonoids are one group within polyphenols, with anthocyanins existing as a group within flavonoids.

Rhubarb accumulates a large amount of anthocyanin in the petiole sections closer to the roots. This means that the red pigment has increased within the cells of the petioles.

Incidentally, the green color is mainly due to chlorophyll. Chlorophyll is an important pigment for photosynthesis and makes plants appear green.

Based on all of this, it seems that the anthocyanin did not decrease during this summer period; rather, because photosynthesis is actively taking place during this time of year, when daylight hours are the longest, chlorophyll naturally became more abundant. Of course, there may be other external factors involved, but considering the proportions, I believe the effect of daylight hours is the most significant.

The order of daylight hours from longest to shortest is summer > spring > fall > winter. Considering growing conditions such as snowfall, rhubarb harvested from fall through winter therefore has the reddest petioles and is the best rhubarb, so to speak, when it is in season. Of course, it also has a rich and distinctive flavor. You can see the difference clearly when it is made into jam.

Today, after finishing the weeding, I experimentally harvested some rhubarb and tried making jam.

These are the jam I made on June 21 of this year and the jam I made today (August 10). The amounts of sugar and lemon juice were the same, and I used the red petiole sections. The amounts in these containers are different because the jam had already been divided into jars.

Rhubarb jam made in June

Rhubarb jam made in August

Please take a look and compare the vividness and intensity of the red color. The rhubarb jam made in June has a rich, full-bodied flavor, with a rich aroma and a pronounced fragrance.

On the other hand, the rhubarb jam I made this time in August has a less intense color. It gave me a stronger impression of being sweet and tart. Even though I specifically selected the reddest rhubarb when experimentally harvesting it this time, when I cut the stalks open, I found that although the surface was red, the core was green. This made me think that there may have been a greater influence from chlorophyll.

This article has been about how seasonal differences in daylight hours may affect the color and flavor of red rhubarb jam. Since seasonal daylight hours may be an important factor when identifying flavorful rhubarb, I hope you will keep this in mind when shopping for rhubarb.

Well, that's all for today!