Spring Pruning and Composting

Diamond Bar enjoys a mild winter climate, but the risk of occasional frost requires pruning techniques unique to a Mediterranean climate. 

This winter has been particularly warm, thus plant dormancy has been limited and plant growth constant. But the risk of frost damage to your garden plants is real should they be hit with one or two nights of temperatures close to or below 32 degrees Fahrenheit. 

If you make the mistake of pruning your evergreen shrubs and plants during winter, they will use stored energy prematurely to leaf out — energy intended for spring foliation. 

If a frost occurs, the new tender growth compelled by early pruning is more susceptible to damage than the established growth would have experienced. 

The plant must then use its stored resources early, and if you prune again and another frost occurs, the cycle continues. 

Likewise, if you have not pruned and frost occurs, it is recommended to leave the damaged foliage in place to insulate the plant from further damage.

The first frost-free date after winter for Diamond Bar arrives mid-February. After that time, it is considered to be safe to prune your ornamental evergreen trees and shrubs without risk of frost damage. 

The proper method of pruning is simply to remove dead foliage, dead wood, and crossing/rubbing branches. An overgrown plant may be safely reduced in height by one third without causing damage. 

In our climate zone, contrary to standard practice, deciduous fruit trees should have most of their pruning done in the summer after fruiting is finished. 

Minor pruning detail can be done in mid-winter after defoliation but before new leaves or flowers emerge. And it's also important to clean-up all the pruning debris to help prevent plant disease later.

As we are quickly approaching spring, now is the time to amend your planting beds. A six-inch layer of compost dug or tilled into your existing soil should be adequate. Additionally, worm compost (vermicompost) can be incorporated at a rate of about one-inch tilled into the planting area.

Compost will improve the friability (texture) of clay soil and improve the water holding capacity of sandy soil. 

Application of a four-inch layer of mulch to the surface of the soil beneath trees and shrubs and in open areas will conserve irrigation water by substantially reducing evaporation from the soil.  Compost will also help prevent weeds from germinating, and provides a finished look to your landscape.

Next week, we'll cover how to make your own compost and start a worm bin and we'll continue providing tips on water conservation.