Final answer:
The term for very drastic pruning is dehorning. This method is typically more harmful to plants and is used as a last resort, with other methods like heading-back, root pruning, disbudding, and thinning-out being less severe.
Step-by-step explanation:
The correct answer to the question 'Very drastic pruning is called _____?' is c) dehorning. Dehorning is a term used to describe heavy pruning that significantly reduces the size of a tree or shrub. It is often a last resort method because it can be harmful to the plant, making it more susceptible to diseases, pests, and environmental stresses. Other options, such as heading-back, root pruning, disbudding, and thinning-out, refer to less severe forms of pruning aimed at promoting health and growth in plants and trees.
For example, heading-back is when you cut a plant back to stubs with the aim of encouraging new growth. Root pruning involves trimming the roots of a plant, typically to prepare for transplanting or to control growth. Disbudding is the removal of buds to shape the growth of a plant or to improve the quality of remaining flowers or fruits. Thinning-out is removing some branches to improve light and air flow within the plant canopy. However, when the drastic pruning is performed, it is often referred to as dehorning, which can be considered for removing or clearing away excess tree growth, sometimes done in the context of land clearing for farming and ranching.