Generally, there are hollow rods with solid knots at intervals. Leaves come out from both sides of the knot in turn, and the leaves with the same knot are born on a plane with parallel veins. Each leaf is divided into three parts, the lower part wraps the pole, and the upper part is independent, with a film or a circle of fine hairs between them. Flowers are small, have no petals, and are pollinated by the wind. The fruit is caryopsis.
Common weeds mainly include the following:
Millet, Gramineae. Also known as "grasping the root grass" and "chicken claw grass".
Morphological characteristics: the base of the stem begins to tilt, and it is easy to take root after landing between nodes, smooth and hairless, with a plant height of 40- 100cm. Leaf blade is lanceolate, strip-shaped, both sides are sparse or hairless, leaf sheath is shorter than internode, and there are many soft hairs with warty base; Ligule obtuse and round membranous. Racemes 3- 10, arranged in fingers, and the lower part is nearly whorled; Spikelets are usually twins, one with stalks and the other with sessile stalks; The first glume is small, the second glume is long, and the edge is ciliated; The first lemma is as long as the spikelet, with 5-7 veins, with unequal vein spacing and hairless, and the second lemma covers the palea. Caryophylls are oval and transparent. Seed propagation. The difference between red crabgrass and red crabgrass is that there are only 3-4 racemes, 2-8 cm long, and 2-3 spikelets are planted on each node of the spike axis; The first lemma is 5-veined, with rod-like hairs between veins and edges; The second lemma is dark brown when it matures.
When the temperature is lower than 20℃, the crabgrass germinates slowly, and it germinates fastest at 25-40℃. The optimum relative humidity for seed germination is 63%-92%. The optimum depth is 1-5cm. The moist and fertile plots are flourishing, which occur in large numbers from late April to late June, bear fruit from August to June, and the seeds fall off when they are mature, with strong vitality. Mature seeds have dormancy habits. Cauliflower is one of the most important weeds in late spring, and it is mostly found in wetlands on banks, fields or wilderness.
Barnyardgrass belongs to the genus Panicum. It is also known as barnyard grass, barnyard grass, barnyard grass, etc.
Morphological characteristics: the stalks are clustered, with bent or erect knees at the base, and the plant height is 50- 130 cm. Leaf blade strips, glabrous; Leaf sheath smooth and leafless tongue. Panicle slightly spreading, erect or curved; Racemes are usually branched, oblique or adnate; Spikelet has two oval flowers, about 3 mm long, with verrucous hairs, densely distributed on one side of spike axis; Glumes have 3-5 veins; The first lemma has 5-7 veins, and the apex has 5-30 mm awn; The top of the second lemma is pointed, rough and spore-like. Lilacs are beige and oval. Seed propagation. Seeds ovoid, oval, yellow-brown.
Ecological characteristics are common weeds in ditches, paddy fields and their surroundings, which are born in wetlands or water. It can germinate when the average temperature is above 65438 02℃. The optimum germination temperature is 25-35℃, which is lower than 10℃ and cannot germinate above 45℃. The germination rate is the highest when the soil is moist and there is no water layer. The seeds of barnyard grass with a soil depth of more than 8 cm do not germinate and can be dormant for the second time. In dry soil, the emergence depth is 0-9 cm and the emergence rate is 0-3 cm. Barnyardgrass in Northeast China and North China began to emerge in late April, and grew until mid-August, usually heading and flowering in early July, with a growth period of 76- 130 days. There is a peak in Shanghai in early and middle May, and there may be another peak in September.
White grass is a perennial herb of Gramineae.
Morphological characteristics: The culms are solitary or clustered, erect, with a plant height of 30- 120cm. The leaf blade is strip-shaped, the leaf sheath is hairless, and some scabbard mouths and edges are hairy. Ligule short and hairy. Spike panicles are cylindrical; The main shaft is angular, with or without hairiness and short branches; Branchlets setae white to brownish purple; There are 1-2 flowers on the spikelet, which are solitary or 2-3 flowers clustered in the involucre; The first glume is very small; The second type is spikelet 1/2-3/4 with 3-5 veins; The first lemma is as long as the spikelet; The grain is almost as long as the spikelet.
Ecological characteristics like to grow in dry places on hillsides or roadsides, and are common weeds on the edge of the ground and in nurseries.