A visual guide to key stages in the growth and maturity of field pea

Page last updated: Tuesday, 26 September 2017 - 10:08am

Please note: This content may be out of date and is currently under review.

Many farm operations rely on a clear understanding of the stage of crop development. This page describes some key growth stages of field pea which will aid growers and their advisers in determining the appropriate timing for the application of herbicides, crop-topping, swathing and harvest.

Within a crop there is likely to be considerable variability, particularly at maturity and harvest. Therefore, it is often necessary to estimate either the average or majority development stage of a crop. At first this is best done numerically, but with experience it can be estimated by eye.

Know your nodes

Counting the number of nodes on the main stem of field pea is the key to safely applying herbicides (Table 1). It is the system researchers around the world use when testing new herbicides and the system most labels use.

Individual field pea plants will have a dominant main stem and several basal branches, with the main stem simply being the longest one you can find. All references to node number on labels and so on refer to the number of nodes on the main stem.

Table 1 Post emergent herbicides and field pea crop stage
Herbicide Crop stage (as per herbicide label)
Grass herbicides From 2-node
Metribuzin 3-node
Imazamox Do not apply beyond the 4-node stage
Diflufenican After 3-node and before flowering
Flumetsulam 2-node to 6-node, no later than six weeks after emergence
Cyanazine Between 3-node and 5-node stage
MCPA Na 6-node to 8-node, 10-15cm tall. Do not apply if flowering has begun*
Paraquat No specific crop guide on label. In practice, when 75% of the crop has brown pods
Diquat As soon as crop has reached full maturity
Glyphosate At or after crop maturity. When average seed moisture content is below 30%

* Varieties grown in Western Australia are unlikely to be at 6-node to 8-node when flowering.

When field pea emerges, two small scale or scar leaves appear. The scar leaves do not form stipules and are therefore not counted. This is best shown in Figure 1 which is at the 3-node stage. When counting nodes, only count those where the stipule leaves are fully unfolded.

Conventional and semi-leafless field pea plants showing tendril, and leaf nodes
Figure 1 Trailing field pea (left) and semi-leafless field pea (right) at 3-node stage

Seed filling, maturity and harvest

Most field pea crops in Western Australia are crop-topped to even up maturity and reduce weed seed set. Swathing is gaining in popularity, particularly with semi-leafless varieties which are less prone to shedding and blowing in the wind. It is important to get the timing of swathing, crop-topping and harvest right, to maximise yield and grain quality. This is best done by measuring the average seed moisture content (ASMC). For example, swathing should begin once ASMC reaches 45%, crop-topping at 25-30% and harvest at 14-16%.

ASMC can be ascertained in a number of ways:

  • Pick 10-20 stems at random and sub-sample sufficient seed to fill a moisture meter, which works well for harvest samples but is not very accurate with high moisture samples near swathing and croptopping.
  • Pick 10-20 stems at random and sample all the seed, weigh the wet sample and then desiccate/dry until constant weight. ASMC (%) = 100 x (wet weight-dry weight)/wet weight.

Alternatively, the appearance (colour, opacity) or texture of the pods, the seed or whole plants (for example, percent maturity) may be used to estimate the correct timing of these operations (Figure 2 and 3).

 Appearance of crop, pods and seed at a range of seed moisture contents
Figure 2 Appearance of crop, pods and seed at a range of seed moisture contents, Boyup Brook, 2005. ASMC = average seed moisture content of whole plant

Estimating seed moisture content by seed colour
Figure 3 Seed colour can be used to estimate the seed moisture content (SMC). Texture can also be used: above 80% SMC, the seed is small, watery and easily squashed; at 40-80% SMC, the seed is easily split with fingernail pressure; between 25-40% SMC, the seed rapidly dries down and is firm but the seed dents with fingernail pressure and will split with increasing force


Funding was provided by the Grains Research and Development Corporation and the Department of Primary Industries and Regional Development.


Mark Seymour