1. Some red stems are caused by the tea tree variety itself, which is red when growing on the tree, also known as purple tea or purple buds.

2. Tea leaves picked in the morning were not spread out in time to cool, trapping heat and overheating the leaves; this is an issue with the withering process of Pu'er tea. During tea sourcing, some ancient tea gardens with large tree ages and excellent tea quality are far from tea farmers' homes. Picking tea early in the morning and walking 2-3 hours to return home makes timely withering impossible, leading to red stems. This is unavoidable, as it is impractical to set up withering troughs at every remote ancient tea garden due to high investment costs for farmers. Therefore, the problem of delayed withering due to long picking distances cannot be solved immediately. The tea itself is of good quality, but the flaws caused by these objective factors require time to gradually improve and perfect.

3. During fixation and rolling, moisture was not thoroughly removed from the tea leaves, so residual moisture remained in the leaves, resulting in red leaves and red stems after drying; this reason can still be attributed to the second point, where the withering process was insufficient or来不及做萎调使得杀青时叶片和叶梗的含水量过多。从茶叶采摘后到进行萎调，间隔时间过长，茶叶被捂到后再进行萎调造成杀青揉捻后红梗红叶比较多。 inadequate, or there was no time to carry out withering, leading to excessive moisture in the leaves and stems during fixation. If the time between tea picking and withering is too long, the tea leaves become "smothered," and subsequent withering results in more red stems and leaves after fixation and rolling.

4. Handmade raw tea is more prone to uneven fixation or improper spreading and cooling, leading to red stems and leaves. Machine-fixed and rolled raw tea is less likely to produce red stems and leaves. However, handmade Pu'er tea tends to have a more vibrant and lively taste, while machine-made tea may lack vitality and appear somewhat dull in flavor.