Grass Plant Structure and Growth - Seasonal Plant Growth
During the short days and cool temperatures of late fall, mature shoots of cool season grasses go through a permanent biological change. That is, the crowns cease to produce just leaves and stems and "switch" over to crowns that will give rise to flowering shoots during the long days and warm temperatures of late May through June (Figs. 3.4 and 3.5).
Figure 3.4 Kentucky bluegrass in flower.
Figure 3.5 Close-up of Kentucky bluegrass flower cluster (botanical term: panicle)
A significant portion of shoot growth that occurs during spring is the production of flowering stems. However, since regular mowing is being done during this period, flowering stems often go unnoticed in home lawns.
Once the grass shoot has completed its flowering cycle, it dies along with its associated roots. Since these dead shoots are continually being replaced by new ones and those which were not mature enough to flower, there is little detectable difference in the lawn. It may just appear somewhat thinner by the end of June or early July. Rejuvenation of the grass plant begins again in late July or early August and the process starts over (Fig. 3.6).
Occasionally, the observation of these flowering stems raise questions about there being a 'weedy' "undesirable" grass growing in the lawn. The natural occurrence of flowering stems on the cool season grasses will be much more noticeable when mowing heights are quite high. These flowering stems are quite tough and coarser in texture compared to the grass leaf blades. Nonetheless, there are cool season weedy grasses that can show up in our lawns and that will bloom during this similar time period. If the flowering grass also looks different or has a different growth habit from Kentucky bluegrass or fine fescue, then getting it identified and determining whether or not control is needed could be pursued.
In a similar manner, lawns often look thinner towards the end of June and early July because a large amount of dry and brown stems seem to have "just appeared." These are indeed the dead and dry grass stems from those shoots that have just recently flowered. They will eventually drop back and decompose in the lawn surface and will ultimately disappear from sight as new shoot and leaf growth reinitiates a little later in the summer. Again, while sometimes unsightly, this is the result of an entirely normal growth process that will resolve itself as the growing season progresses.