Weekly Garden Tip

January 16, 2006

By Gene Joyner, Extension Agent
Palm Beach County Cooperative Extension Service

A lot of things slow down their growth in the winter, but I guarantee you there’s one type of plant that doesn’t and that’s various types of weeds. Many people complain that the bulk of their time spent outside gardening is spent trying to combat weeds from overtaking the rest of their landscape and I agree because I spend a lot of time weeding as well.

During the winter months a lot of cool season weeds that you never see at other times of the year appear almost as if by magic and combine with the perennial and warm season weeds that are already out there. Some people have a much worse weed problem in the winter months than they do during the rainy summer season.

If you want to combat weeds in your landscape, you don’t have a whole lot of choices. You can get out there in small areas and hand pull them or you can put out various types of ground cloth, plastic, or other materials as physical barriers. Natural mulches though are probably the better thing to use in many people’s opinion and there are many types of mulching materials available at local retail garden centers. Many people like the decorative bark mulches which now come in a wide variety of colors in addition to the natural color.

When using mulches the depth of the mulch is very critical to it’s success. Normally 3 to 4 inches of mulch is recommended initially because over a period of several weeks it will compact down and if it’s not too thick there will be cracks developing that allow weed seeds to filter through and reach the soil surface where they germinate. By putting mulch down initially 3 to 4 inches, even after it compacts you’ll have a thick enough layer to maintain a weed free flower bed for probably 6 to 9 months. After that you would need to add another inch to an inch and a half to freshen it up and extend the life of it.

Mulches also as they decompose will add nutrients back to the soil so if you have very poor sandy soil which most people do over a period of years of mulching you can build up some excellent black topsoil. Many people worry about mulches harboring ants, termites or other pests, but this is not a major factor for most people. If these insects do invade mulched areas, the mulch can be sprayed with pesticides to kill these insects before they would be a threat to your home.

Some people use stone mulches or gravel mulches. These work well, too, but only for a few years. Over time wind blown sand fills the cracks in these type mulches and then you get weeds growing in the stone mulches which makes it difficult to control.

Some people also say that stone mulches do not allow the soil to dry out quickly during the wet summer season and by keeping the soil wetter this can aggravate soil borne diseases or root rots for certain types of plants. A few stone mulches are also highly alkaline and over time will leach into the soil making plants a little bit unhappy particularly if they are acid loving plants.

If you have questions about mulches in your gardens or which types last the best, contact the Palm Beach County Extension office for free advice. Dial 233-1750 in the north and central county area or 276-1260 in the south county area.