Source: http://vasat.icrisat.org/?q=node/199

There are 4 types of groundnut plants based on the growth habit and other characteristic:

 

• Spanish (bunch),

• Virginia (bunch),

• Virginia (runner) and

• Valencia (bunch).

 

In the Spanish (bunch) group, the plants (Due to intra specific hybridization to develop new varieties,these specific characteristics of different types can sometimes get blureed)

 

• grow erect,

• possess light-green leaves,

• have round, plump non-dormant seeds, with light-rose testa,

• small pods, rarely have more than 2 seeds/pod,

• produce pods in clusters at the base of the plant, and

• popularly cultivated type.

In Virginia bunch and runner type,  (Due to intra specific hybridization to develop new varieties,these specific characteristics of different types can sometimes get blureed) the branches crawl either partially or completely on the surface of the soil, produce large pods all along them, possess dark-green foliage, have oblong, dormant brownish seeds and late maturing but yield higher than bunch ty

In Valencia bunch type,  (Due to intra specific hybridization to develop new varieties,these specific characteristics of different types can sometimes get blureed) very sparse branching habit dark green foliage seeds long or short seed coats purple, red, russet, or tan many pods may have 3-4 seeds most suited for consumption as boiling type

             Spanish Bunch type                                      Virginia spreading type

Observe branches and pod setting in the above two types
After sowing, seedlings emerge in 5-10 days, depending on sowing depth, soil moisture, and prevailing temperature.
Bunch types do not possess seed dormancy.
But seed of spreading types have a dormant period of 1-6 months, after harvest, depending on temperature and storage conditions.
However, the dormancy can be broken by heat treatment or ethylene treatment using ethrel.

The plants usually grow slowly until about 40 days after planting.
Peanut plants start flowering about 25 to 40 days after planting.
Growth is more rapid between 40 to 100 days. During this period a four- to five-fold increase in peanut foliage occurs.
Groundnuts can flower (orange yellow) over a long period (20-60 days), depending on moisture availability, and temperature.
The flowering period is considerably shorter in bunch type of cultivars than in spreading types.

The flowers are born in axil of leaves mostly near the base of plant.
It is a self pollinated crop i.e its own pollen fertilizes the ovule
After fertilization stalk of ovary elongates and forms peg which contains fertilized ovules at the tip.
The pegs penetrate the soil up to a depth of 7 cm and then grows horizontally when the ovary starts developing as a pod containing seeds

• Growing ovary. 

• Aerial peg, 5 to 7 days. 

• Peg soil penetration, 8 to 12 days.

• Beginning of pod enlargement, 14 to 21 days.

• Early stage in pod development.

• Immature pod.

 

 

Normally 60-80 days are required for pod development from flowering to maturation in spreading types and slightly less than that (50-60 days) in bunch types.
Vegetative development declines during pod filling.

(Stages of pod development after Smith,1950) 

Bunch type takes 90 to 110 days to mature and spreading cultivars mature in 110 to 130 days under warm conditions.