by Chris Sigurdson, Peninsula Landscape Supplies Ltd. –
Mulching will greatly benefit your landscape at any time of the year. Annual mulching:
• Aids in the retention of soil moisture by preventing evaporation of water in subsoil, which is especially important for evergreen plants that do not drop their leaves.
• Helps control soil temperature by acting as an insulator, keeping roots cooler on warm days and alternately, warmer on cool days.
• Prevents soil erosion, and helps to maintain soil nutrients. Remember, a productive soil should be comprised of at least four to five percent organic matter.
• Promotes biological activity in soil which helps to improve soil structure and tilth, thus improving plant growth.
• Helps with weed suppression.
But how do you choose which mulch is best for you? Typically on the Island, a majority of the mulches you will encounter for home use are bark-based mulches or compost-based mulches. Which mulch you use, however, should be based on the application.
Bark-based mulches offer great weed suppression, are a good value, and they look great! You will also get longevity out of bark mulch depending upon how fine or coarse it has been ground. Bark mulch is great to use around trees and shrubs. It should not be used as mulch in vegetable beds or any other bed that is cultivated on a regular basis to prepare for planting. When bark is incorporated into soil it creates an imbalance that immobilizes nitrogen, thus creating a nitrogen deficiency in the soil that will affect plant growth. When using bark mulch it is advisable to supplement with nitrogen prior to applying the mulch to minimize these effects. Also, please keep in mind that bark mulch is generally more acidic (2.0 to 5.0) so take care if you are applying it near pH-sensitive plants.
Compost-based mulches are generally more expensive than bark mulches. Aside from this, they offer all the benefits of bark-based mulches and more. Properly prepared compost is a significant source of nutrients and organic matter, and regular applications will help reduce fertilizer requirements. One of the best reasons to use compost mulches is that they have had time to properly decompose. This is especially important if you are using compost to mulch vegetable and other regularly cultivated garden areas. Because of the state of decomposition of compost mulch, if it is eventually mixed into the soil it does not create an imbalance and immobilize nitrogen as would bark mulch. It will actually increase the nutrient holding capacity of your soil, a much healthier choice for plants. There are many different types of compost mulch, and when selecting one it is important that you make sure that it has been composted at high temperatures to kill pathogens and weed seeds before applying it to your planting areas, especially if you are using it on crops! So, do your homework and if possible, ask for an analysis before making a purchase.