4 MISSOURI AGR. EXP. STA. RESEARCH BULLETIN NO. 21 



were extreme cases as the trees had been greatly weakened from 

 various causes which resulted in an early cessation of growth. The 

 rest period probably begins in a given twig shortly after the forma- 

 tion of its terminal bud. It has been observed that apple trees of 

 normal vigor form a large number of terminal buds the latter part 

 of June or early in July under Missouri conditions. Under similar 

 conditions, a peach tree would continue growth until later in the 

 season. 



Not all the twigs of a tree begin their period of rest at the same 

 time. It is probably safe to say that deciduous trees and shrubs 

 usually begin to enter their rest period in July, and thruout August 

 and September become gradually more and more dormant until com- 

 plete defoliation occurs and all ordinary vegetative processes cease. 



Herbaceous perennial plants have not been carefully studied 

 with regard to the exact time of entering the rest period. However, 

 it has been observed that several species at least cease growing in 

 late July or early August. The cessation of growth is marked by the 

 formation of strong buds on the crown of the root stock. Many 

 plants of this kind continue growing until the approach of cold 

 weather, when vegetative activity ceases as indicated by the forma- 

 tion of resting buds. While the rest period of woody plants continues 

 into the winter, and may even last until spring in some species, it 

 probably does not persist so late in herbaceous forms. Some of these 

 seem capable of growing shortly after they become dormant in fall, 

 while practically all that have been experimented with seem able 

 to begin growing without treatment after a dormant period of two 

 months or less. It may, therefore, be said that the rest period in 

 woody plants in most cases lasts from two to four months; in her- 

 baceous species it probably will not last on the average more than 

 two to six weeks. 



Bulbs begin their rest within two to four weeks after flowering. 

 As soon as the leaves of such plants have died, the bulbs may be said 

 to be in the misdt of their period of rest. The rest period of bulbs 

 commonly lasts from June until late fall or early winter, or in other 

 words, from one to six months as regards root growth, and five months 

 longer if the time that actually elapses before leaves or flowers appear 

 above ground under natural conditions is considered. Practically 

 all bulbs resume top growth in December, if supplied with heat and 

 moisture. The same is true of some species of woody plants and a 

 great many herbaceous forms. The rest period of a seed may begin 

 at maturity, or during the curing process which lasts from one to 

 four weeks after harvesting. The length of the rest period in seeds 

 varies as greatly as it does in woody and herbaceous plants. In fact 



