Root Ball Care and Maintenance

Introduction

Roots and shoots are the two ‘power stations’ of plants. Foods in the form of starch are manufactured in shoots (source) and dispersed through the intricate networks of phloem to various organs but stored mainly as long-term storage in the roots (sink). Depending on the plant category, root architecture differs between the monocots and the dicots. Monocot plants have fibrous root system (losing the main tap root after seed germination) and dicot has the tap root system. During seed germination, the initial stage is primary root growth (auxin regulated growth), root hairs and followed by the secondary, tertiary as so forth, to develop elaborate root architecture. Within this system, the root hairs play the significant role in water and nutrient absorption. Root hairs are responsible in 50% of phosphorus uptake1 and water absorption2 as root hairs increase the surface area for absorptions. A tree growing in an undisturbed site has a tap root and horizontal root spread that is 2.5-3.0 times greater than the crown spread3.

Function of roots

Water and nutrient absorption

  • Water and nutrient uptake begin from soil into the xylem tissue in the roots and flows upwards towards the leaves for photosynthesis and food is transported through phloem tissue back to the roots.

Food storage

  • Food supply for plants is stored in the form of starch in specialized root cells
  • Some roots become modified mainly for food storage such as the primary roots in carrots, sweet potatoes, beet, turnip, and cassava.

Anchorage

  • Roots act as the anchor and some tap (primary) root can grow as deep as 1- 1.5m (oak), 2-3.5 m (Red Woods), 4.5m (White Oaks), 3m (Walnut), 2m (Hornbeam), to name a few. The depth of roots however does not always correlate with the size of plants. Some smaller plants adapted by producing adventitious roots or tendrils to clinch on surfaces that it can cling on. The number of straight roots in the root ball have been associated with improved anchorage, whereas roots deflecting downward or around the trunk appear to reduce stability4.

Vegetative reproduction

  • The eradication and control of Horsetail or marestail are challenging because of their dynamic and aggressive root system.  To totally eradicate marestail is almost impossible because when it is pull out, fragment of roots that remain can regenerate new seedlings.

Root and wired root ball tree

Transplanting trees is advantageous because they provide instant trees and hedges. It has become a common practice in horticulture and landscape where trees have the capability to survive stresses from transplanting. Nevertheless, it still requires care during extraction, before planting and after planting. Transplanting stresses trees because 95% of the root system is removed when the tree is dug3.

(a) Taxus baccata in root ball (RB)                                                                              

 (b) Taxus baccata in wired root ball (WRB)

Factors causing damage and poor root growth in root ball

  1. Rough handling during loading and unloading

Trees should not be lifted by the trunk. Rough handling of the root balls causes more damage to fine root hairs

  • Acclimatisation

The term acclimatisation is defined as the process of becoming accustomed to a new environment. Moving plants from their native environment to a new one may include the change in elevation, temperature, salinity, photoperiod, and soil types. It generally would need at least three months for plants to be retained in a new site (provided with proper care) before transplanting.  Plants experienced shock when they are not gradually introduced into their new environment.

  • Lack of water

The root ball during storage requires regular watering for better lateral root structure. High mortality rates among most species of nursery tree after transplanting is attributed to water stress5. Drought stress or stress from water deficit can be reduced by applying mycorrhizae before transplanting.

  • Soil compaction

The effects of soil compaction are usually observed after transplanting. Fine roots near the ground surface are responsible for water and nutrient uptake and regular trampling on the ground surface underneath the canopy can cause damage to fine lateral roots. In some garden, mulches are applied underneath the tree canopy to deter weed growth and to retain moisture.

  • Fertilisation after planting

Fertilising after transplanting is known to be ineffective until the root system is fully established. However, the presence of mycorrhizae provides optimisation of water and nutrient uptake from the soil.

  • Root ball coverings

The burlap used as a covering is degradable but removing burlap and wire during planting is an ongoing debate. Until there is a definitive answer, it is more advisable to remove the covering to allow roots a higher probability to adapt to the new soil environment and root growth is less restricted.

  • Pest and disease

Because roots are injured during extraction at the site of origin, roots become more susceptible to pest and disease.

By Dr Nur Abdullah

References

  1. Ruiz et al. (2020) Plants and Soil 447:281-304
  2. Carminati et al. (2017) New Phytologist 216(3): 771-781
  3. Harris & Bassuk (1993) Journal of Arboriculture 19(2): 64-70
  4. Gilman and Orfanedes (2012) Journal of Environmental Horticulture 30(4):173-181
  5. Dixon et al (2015) Acta Horticulturae 1085:119-127.