While delicious, the humble peanut (Arachis hypogaea) is the victim of misinformation. First off, this food is not a nut. It’s a seed pod, like other legumes such as peas and soybeans. Second, peanuts do not grow from the mother plant’s roots (although they do, as most people know, grow underground!).
There’s a lot of exciting stuff happening in the growth cycle of a peanut plant. If your interest is piqued, there’s good news ahead. This article will walk you through the peanut plant growth stages, and I’ll also give some tips and tricks for trying your hand at cultivating peanuts yourself.
- Conditions for Growing Peanuts
- Peanut Plant Growth Rate
- Growth Stages of a Peanut Plant
- When to Harvest Peanuts
- Peanut Plant Growth Stages FAQs
Conditions for Growing Peanuts
Peanuts are native to the tropical climates of South America. Though we don’t know much about the archaeological history of the peanut, we do know that evidence of the food can be found as far back as 3,500 years ago.
Because of this, it shouldn’t come as much of a surprise that peanuts enjoy warm weather. In the United States, for example, peanuts are commercially grown in Hardiness Zones 8 to 11. Gardeners in cooler climates sometimes keep peanut plants in containers (the growing season can then be ‘extended’ by moving the containers indoors when cold weather arrives).
Peanut pods develop within the soil around the plant. So, keeping the surrounding area free of debris and competing weeds is extremely important. The soil also needs to be soft enough for the plant’s pegs (more on this later on) to penetrate.
Your peanut plants should be placed somewhere with at least 8 hours of direct sunlight daily. Plants thrive in temperatures around 86 to 93°F. Conditions hotter than this can damage the flowers and interfere with pod development.
Also, peanut plants utilize calcium in the soil to produce healthy seeds and pods. For this reason, it’s common practice to amend the top layer of soil with a good source of calcium — e.g., bone meal.
Peanut Plant Growth Rate
It takes an average of 120 to 150 frost-free days for peanuts to mature and prepare for harvest. Most peanut plants reach 2 to 3 feet in height at harvest.
Clemson University says the first 40 days of growth are pretty slow. Growth then speeds up considerably from about day 40 to day 100. During this time, the peanut plant’s foliage can quadruple or quintuple!
After this period of immense development, the plant then slows back down to focus on pod and seed development. Of course, since this process happens beneath the soil, there’s not much for the gardener to see.
Growth Stages of a Peanut Plant
The cultivated peanut plant is a herbaceous perennial most often grown annually. New peanut plants are started from seed each spring and harvested the same year in the fall.
The peanut plant’s natural life cycle is cut short in this way because the plants must be dug up to access the harvestable seed pods. There’s no easy way for commercial growers to do this while saving the original plant!
Whether in the context of an industrial peanut farm or the home garden, here’s a closer look at the life stages each peanut plant goes through:
1. Seed Germination
As mentioned above, peanut plants are started directly from seed each season. And, in case you didn’t already know, the seeds of a peanut plant and the peanuts we eat are the same!
You can get a small glimpse into the anatomy of a peanut seed by looking at a husked peanut. The two halves of the peanut are the seed’s cotyledons. The little nub at the bottom of one of the halves is the seed’s embryo, which would eventually turn into the plant’s first root and shoot.
2. Seedling Emergence
Once germination begins, the seed’s radicle (primary root) will first grow into the soil. Then, the plumule (primary shoot and leaves) extends upward and breaks through the soil’s surface. This is known as ground cracking.
The vast majority of garden plants are epigeal. This means that the cotyledons grow up and emerge from the soil early in the seedling’s life. Peanuts, however, are more accurately described as hypogeal, meaning the cotyledons usually stay beneath the soil.
3. Root Development
The roots of a peanut plant grow incredibly fast. Peanut root systems can grow 12 inches deep within just ten days and reach over 36 inches deep in 60 days. By the end of the growing season, these roots can penetrate more than 70 inches (or 6 feet) into the soil!
4. Vegetative Growth
Peanut plants mature into full, leafy bushes. The leaves are distinct, boasting four leaflets, a piece that resembles other legumes.
The first flowers will start appearing 40 or so days after planting. Peanut plants have bright yellow, pea-like flowers.
Since edible peanuts are a type of fruit, flowers must be fertilized for production. Fortunately, peanut flowers are 100% self-fertile. Outside pollination from insects or the wind is unnecessary.
This is perhaps the most exciting phase of the peanut growth cycle. Fertilized flowers will drop their petals and, after about seven days, begin to elongate toward the ground. This elongated stem, called a peg, continues growing until it penetrates the soil. The peanut pods will develop along the underground portion of the peg.
Different peanut plant varieties can be grouped based on growth habits:
- Bunch peanuts produce their pods in clusters at the very ends of the pegs.
- Runner peanuts have their pods scattered along the lengths of the pegs.
7. Pod Development
The peanut pods will start to swell, reaching full size in 21 to 30 days. Only the outer husks are mature at this point, however, and it usually takes 60 to 80 days for the edible kernels inside to fully develop.
When to Harvest Peanuts
Peanut pod development is greatly affected by the general growing conditions throughout the season. Since you can’t quickly check the progress of your peanut harvest as you could, say, a tomato, the best way to monitor development is to dig up a couple of plants at an estimated maturity time and check the pod contents. The peanuts are ready to harvest when the seeds fill out the pods.
If you enjoyed this article, here’s a link to Banana Plant Growth Stages that you may also enjoy.
Peanut Plant Growth Stages FAQs
How long do peanuts take to grow?
Peanut plants require an average of 120 to 150 days to fully develop. Green peanuts that are purposefully harvested early may be ready in as little as 90 to 110 days.
How many peanuts can one plant produce?
A healthy peanut plant can produce up to 50 individual pods in a season. The average is closer to 40. Keep in mind that runner varieties tend to be more productive than bunch peanuts.
- Clemson University Peanut plant growth and development
- University of Wisconsin Peanut plant cotyledon development
Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.