Plants are much more complex then you might think. They are not able to move around like animals. Therefore plants have to cope with the conditions at the place they were placed as a seed. Some plants have developed rather clever strategies. This gras for example (Poa alpina) occurs in the alps in a harsh environment. Because the growing season is very short and the life cycle (growth, produce flowers, make ripe seeds, seeds establish and growth) may not be completes in one season, the plant has developed a strategy called vivipari (born alife, like animals). It does not produce seeds but little seedlings. These have the advantage that they are already bigger than seeds and this enlarges the chance to survive.