The growth characteristics of tall fescue plants undergird the management programs suggested here. Although tall fescue growth regenerates in essentially the same way as perennial ryegrass, there are some important differences. The rate of new tiller formation in tall fescue is about one-third that of perennial ryegrass, but tall fescue tillers survive longer and are much larger. When leaf stage is used to determine whether a pasture is ready to be grazed, tall fescue plants should have 2 to 3 leaves, as compared to 3 to 3.5 for perennial ryegrass. The initiation rate of new leaves also seems to be slower in tall fescue than in ryegrass, even though tall fescue leaves can grow to heavier weights. For these reasons, the majority of biomass accumulation in tall fescue is from regrowth of remnant leaves rather than from the formation of new leaves, as occurs with ryegrass.
In Mediterranean tall fescues, energy reserves accumulate mostly in the stem bases in late spring, showing sometimes as a swelling of the tiller base. These reserves are used for survival during summer dormancy and for regrowth in autumn; thus, tiller bases (3-5 cm) must remain ungrazed or uncut during summer periods. Continental tall fescues store energy mostly within the tiller bases, most of which are buried below the soil surface in established plants. This allows for good regrowth after close grazing, before photosynthesis in the leaves generates carbohydrates. When soil moisture is adequate for immediate regrowth after grazing, low grazing heights will have minimal effect on pasture growth or persistence. In drought conditions, however, grazing of fresh regrowth can reduce persistence by depleting carbohydrate reserves that cannot be replenished.
Leaf axillary adventitious buds that develop into daughter tillers during development of reproductive stems in spring are very important for continued summer production. These tillers will survive only if the reproductive stems are removed before they flower, so spring stem control is important. Some axillary buds that do not develop into tillers in spring will form rhizomes, that is, underground stems that produce new growth aboveground, the following autumn. These short rhizomes do not extend as far as those of some other grasses, such as couchgrass [Elymus repens (L.) Gould subsp. repens = Agropyron repens (L.) P. Beauv.] or phalaris. They arise in late autumn, for the first time about 2 yr after establishment. The growth of these rhizomes can be encouraged with N fertilizer, resting spells between grazings, and higher stubble heights. Long spells between grazings in autumn result in more rhizome growth and are an important aspect of management to increase plant density in tall fescue pastures. Spread of plants by rhizome activity is particularly noticeable in flood-irrigated tall fescue and is one of the reasons that it has such better persistence in this environment than ryegrass.