Article in English: It is important not to pull any stalks in the plant's first year of growth. It will weaken the young rhubarb plant. Allow each rhubarb plant to establish a strong root system the first year and leave the stalks intact. Start harvesting during the plant’s second season.  If the plant looks very healthy, you can harvest 1 to 2 stalks during its first year. But this is an exception. A rhubarb plant can produce stalks for up to 20 years. Expect to get about 2 to 3 pounds (0.91 to 1.36 kg) of stalks from a mature plant each season. Prime rhubarb season is April to June. A good rule of thumb is to pick your rhubarb no later than July 4. The harvesting period typically lasts about 8 to 10 weeks.  Rhubarb plants are dormant during the fall and winter. If you try to harvest your rhubarb too late, the stalks might get frost damage and be inedible. A ripe stalk should be about the width of your finger. Leave thinner stalks on the plant to continue growing.  Stalks that are too thick will be chewy and tough. Don’t harvest from a plant whose stalks are very thin. That’s a sign the plant is underfed and weak. The longer the stalk, the more flavorful it will be. And while 8 inches (20 cm) is the minimum length before harvesting, stalks that are between 12 and 18 inches (30 and 46 cm) long are the most delicious.  This measurement should only include the stalk itself, not the leaves. Run your hand along the length of the stalk. If it's crisp and firm, it's ready to pick. Contrary to popular belief, how red or vibrant the stalks are does not determine how ripe the plant is. Not all rhubarb is a deep red hue. Some varieties of rhubarb are paler shades of red or even green when they're ready to be picked. Turkish and Riverside Giant are 2 common green varieties of rhubarb.

Summary in Chinese:
大黄生长至少满一年后再将其茎干摘下。 大黄的收获季能从晚春一直持续到仲夏。 检查大黄茎干的宽度是否在1.3cm到2. 5cm之间。 茎干必须长到 20cm才可收获。 颜色不是判断大黄是否成熟的标准。