What is First Flush Matcha? Why It Matters for Every Cup
First flush is one of those terms that appears on matcha labels without much explanation. Most brands mention it. Few explain what it actually means or why it changes what ends up in the cup. Here is the full picture, and why Master's Reserve is first flush without exception.
What first flush actually means
The tea plant goes dormant through winter. From the last harvest of the previous season through to early spring, the plant is in a period of recovery and accumulation. L-theanine, EGCG and chlorophyll build slowly in the roots and stems over the cold months without being drawn into active leaf production.
When temperatures begin to rise in late April, the plant breaks dormancy and channels that stored energy into the first new growth of the season. These are the first flush leaves, picked in a narrow window of two to three weeks in late April to early May in the matcha-growing regions around Kyoto. They are the youngest leaves on the plant. They carry the highest concentration of every compound that makes ceremonial grade matcha worth drinking. And they are available once a year.
What it contains that later harvests do not
L-theanine concentration is at its annual peak in first flush leaves. This is the amino acid responsible for the umami depth, the natural sweetness, and the smooth, sustained focus that quality matcha is known for. It accumulates during the cold months of winter and reaches its highest point in the very first leaves of spring.
EGCG, the primary antioxidant catechin in matcha and the compound behind most of the serious research on what matcha does in the body, follows the same pattern. Highest at first flush. Lower with every subsequent harvest.
Chlorophyll accumulates during the shade-growing period that precedes first flush. Tea plants are covered for three to four weeks before picking to cut off direct sunlight. The plant overproduces chlorophyll in response, which is what gives a genuine first flush ceremonial grade matcha its vivid, almost electric green colour. That colour is not processing. It is cultivation.
What happens after first flush
As the season progresses and temperatures rise, the plant enters its normal growth cycle. Growth accelerates, yields increase, and the stored winter energy is spent. What follows are second and third flush harvests, picked in June and July.
These later harvests serve the culinary and everyday green tea market well. But the compound concentrations drop with each subsequent picking. L-theanine falls noticeably by second flush. EGCG follows. The colour shifts from vivid green to something darker and less vibrant. The flavour moves from naturally sweet and umami-rich toward more bitter and astringent. A later-harvest matcha labelled ceremonial grade is making a claim that the harvest timing does not support.
Why Okumidori at first flush is specific
Master's Reserve is Okumidori from Wazuka, Kyoto. Okumidori is a cultivar that matures later in the season than most, typically around eight days after the more widely planted Yabukita. That later maturation, within the first flush window, means more time on the plant accumulating the compounds that define quality. The L-theanine concentration in Okumidori at first flush is among the highest available from any cultivar in the Kyoto region.
The 21 days of pre-harvest shading that precedes the Master's Reserve harvest is timed specifically to align with the Okumidori first flush window. The shading drives chlorophyll and L-theanine accumulation to their peak. The harvest captures that peak. Stone-milling to 10 microns distributes those compounds evenly through every gram of the final powder.
First flush is not a label applied at the end of the process. It is a decision made at the beginning of the growing season that determines everything that follows.
Why timing and shading cannot be separated
First flush and shade-growing work together. Shading before a later harvest produces some additional chlorophyll but cannot replicate the compound concentration of a genuine first flush leaf. The stored winter energy that drives the accumulation is gone after the first picking. What the shading does to a later harvest leaf is a fraction of what it does to a first flush leaf that has the full winter accumulation behind it.
This is why the combination of first flush, shade-grown, and a quality cultivar from a specific origin matters. Each element amplifies the others. Remove any one of them and the product in the tin is measurably different.
What this means in the cup
A first flush Okumidori, prepared correctly in water at 75 to 80 degrees celsius with a chasen, delivers a specific experience. Natural sweetness upfront. Pronounced umami depth that lingers. A clean finish with minimal bitterness. The vivid green of the suspension in the bowl. These are not subjective impressions. They are the direct output of the compound profile that first flush cultivation produces.
If a matcha tastes flat, bitter or one-dimensional, the harvest timing is one of the first things worth questioning.
Master's Reserve is first flush, every season. Available now, delivered across the United Kingdom.