Grass Plant Structure and Growth - Growth Habits of Grasses
A common growth characteristic of grass plants is their ability to spread out from a parent plant. Growth habit describes the type of shoot growth present in particular grass plants and is directly related to their ability to spread out from the parent plant and ultimately form a lawn.
There are three general classifications of growth habit present in grasses: rhizomatous, bunch-type, and stoloniferous. The specific type of growth habit along with the rate of shoot growth will determine how quickly and easily these grasses will establish a lawn area or fill in bare spots.
Rhizomatous grasses spread by below ground stems known as rhizomes (Figure 3.2).
- These rhizomes terminate in a shoot that emerges some distance from the mother plant. As these new shoots mature they will also produce rhizomes that eventually produce new shoots thus creating a lawn.
- Healthy, vigorous rhizome type grasses such as Kentucky bluegrass tend to form dense, uniform lawns with shoots oriented in an upright position.
- This vigorous rhizome production is why Kentucky bluegrass makes such a good sod. The sod roll is sufficiently held together by these rhizomes such that it can easily be cut at the sod farm, transported and relayed at its destination without it falling apart at any point in this process.
Bunch-type grasses spread primarily or entirely by the production of tillers.
- As illustrated in Figure 3.2, tillers originate from the crown area and grow upward from the base of the plant. It is this type of continuous tiller production that gives the plant a clumpy appearance; hence the name bunch-type grass.
- Seeding rates need to be higher when bunch-type grasses are a significant portion of the seed mixture or blend. When seeding rates are too low or where growth develops from individual isolated plants, small clumps are formed creating a non-uniform lawn surface.
- Common cool season lawn grasses associated with this type of growth habit are perennial ryegrass, tall fescue, hard fescue, and chewings fescue.
Stoloniferous grasses spread by lateral stems called stolons, which creep over the ground and give rise to new shoots periodically along the length of the stolon (Figure 3.2).
- Lawns formed from these types of grasses appear to have their aerial shoots growing laterally along the ground rather than upright as in bunch or rhizomatous grasses.
- Creeping bentgrass is a good example of this type of growth. When it is mowed at heights greater than 3/4 inch, it forms a relatively loose, 'puffy' mat of grass with most aerial shoots growing horizontally.
- In bluegrass lawns, creeping bentgrass is usually considered a weed.
- Creeping bentgrass is considered very desirable on putting greens, croquet courts and other fine turf areas as it will adapt to very low mowing heights (i.e., about 1/4 inch or slightly less) and create a very smooth, uniform playing surface.
Root growth also originates at the crown. However, roots continue to lengthen and grow from the root tip as opposed to the growth of shoots and leaves which are pushed upward and outward from the crown. Roots are naturally sloughed-off and new ones regrow as a normal part of grass plant growth. Also, adverse environmental conditions can significantly shorten the life of grass plant roots. For example, weather and soil stresses associated with drought conditions or excessive rainfall can cause significant root injury and loss resulting in slower growth.