The time it takes to grow a bean plant is not a single fixed number but a variable measured in a concept called “Days to Maturity” (DTM). This timeline is an estimate of the period from planting a seed to the point of a first usable harvest. The final DTM depends entirely on the specific variety planted and the intended use of the final product. Understanding these differences allows a grower to predict harvest timing with greater accuracy.
Understanding Growth Timelines by Bean Type
The two primary types of bean plants, bush and pole, have distinct growth habits that directly influence their time to harvest. Bush beans are compact plants that do not require support, and they typically have the shortest DTM, maturing in a tight window of approximately 45 to 60 days. Because they produce their crop nearly all at once, bush varieties are often favored by those who wish to harvest a large quantity for preservation.
Pole beans, conversely, are vining plants that must climb a trellis or pole, which extends their initial growth phase. These varieties generally take longer to reach maturity, with a DTM ranging from 60 to 80 days. Their advantage lies in their continuous production; once they begin to bear fruit, pole beans will continue to flower and produce pods until the first hard frost.
The ultimate harvest time also hinges on whether the beans are intended to be eaten as “snap” beans or as dried beans. Snap beans, also known as green beans, are harvested while the pod is still tender and the seeds inside are immature, leading to the shorter DTMs mentioned above. Dry or shelling beans, such as kidney or pinto varieties, must be left on the vine until the pods completely dry out and the seeds inside are hard. This process requires the longest duration, often extending the DTM to 80 to 100 days or more.
The Critical Stages of Bean Development
The overall DTM can be broken down into three sequential biological phases. The process begins with germination and emergence, which is the time it takes for the seed to sprout and push its first leaves above the soil surface. Under favorable conditions, this stage is relatively quick, usually taking between 5 and 10 days.
Following emergence, the plant enters its period of vegetative growth and flowering, focusing on developing a strong root system and sufficient foliage. This phase typically lasts for three to four weeks, concluding with the appearance of the first flowers. The plant must accumulate enough energy to support the subsequent pod development.
The final phase is pod set and maturity, which is the time from flowering until the pods are ready for harvest. For snap beans, this period is short, often just one to two weeks after the first flower appears, as the pods are picked while young and tender. For dry beans, this stage is significantly prolonged, requiring the plant to divert resources into fully developing and drying the seeds within the pod.
External Factors That Affect Growth Speed
Environmental conditions can accelerate or delay a bean plant’s journey through its growth stages. Temperature is a significant factor, as beans are warm-weather crops that require a minimum soil temperature of 60°F for successful germination. Planting in cold soil can cause the seeds to rot before they sprout or lead to significantly delayed emergence, extending the DTM by several weeks.
Optimal germination occurs when the soil temperature is consistently in the range of 70°F to 85°F. The plant also requires full sun, meaning a minimum of six to eight hours of direct sunlight daily. Insufficient light reduces the rate of photosynthesis, which slows overall growth. Low light levels can stretch the vegetative phase and delay flowering.
Consistent moisture is necessary throughout the plant’s life, especially during the flowering and pod-setting stages. Drought stress at this time can cause the plant to abort its flowers, preventing pod formation and negatively impacting the final harvest time. Careful management of nutrients is also important, as excessive application of nitrogen fertilizer can encourage the plant to grow lush leaves at the expense of producing flowers and pods, ultimately slowing the development of the edible portion.