Garden mulching survey

I've always strongly advocated garden mulch, especially for people with big country gardens. (We buy wood chip mulch by the dump-truck load.)

So I was interested to read what perennials expert John Valleau, the chief horticulturist for the wholesale grower Heritage Perennials, had to say recently about the results of a reader survey he did on garden mulching techniques.

In his May 2006 Perennials.com newsletter, he had given the standard advice to always taper the mulch down to nothing immediately around the crowns and stems of perennials to avoid problems with rotting.

Then Quebec-based garden writer Larry Hodgson wrote in to say he thought that was all a garden myth. So, John asked his newsletter readers for their observations.

Here's what he had to say about the results in his July newsletter:

I was literally flooded with responses this month. Wow! Mulching must be a very hot topic, and here I was anticipating only a handful of entries.

I've taken some time to analyze the data, and the results for the #1 question on whether to taper the mulch or to pile it evenly around perennials worked out this way:

• 85% — spread mulch evenly over the bed
• 7% — doesn't matter, or depends on the particular plant
• 8% — taper the mulch or rotting may be a problem

BENEFITS of mulching you mentioned included: reduced watering, because the mulch holds the moisture in the soil; cooler roots during summer heat; greatly reduced weed seed germination (figures in the 80% fewer weeds were mentioned a few times); mulches add beneficial organic matter; mulches encourage plenty of soil microbes, worms and other beneficial critters; mulch looks aesthetically pleasing.

The most important thing you reported over and over again is that mulching seems to make your perennials grow better!

Read the entire mulch article. It turns out that you can spread mulch a lot thicker than many experts tell you without doing harm to your perennials.

Mulch by the dump truck

This week we got another dump truck load of wood chip mulch. We seem to go through one dump truck load each year. We top our planting beds with a three-inch layer of mulch, generally straw or wood chips. We do it to control weeds and keep moisture in the soil.

We also like to mulch our trees with leaf mould and wood chips to keep the grass mowable around them. (Otherwise, it's easy to get too close to a tree and injure the bark.)

We buy the composted wood chips cheaply from a tree service, and we get straw for the vegetable garden from a local farmer.

We find that mulch is a godsend for country gardening for these reasons:

• It keeps weeds down, mainly by blocking out the light they need to germinate – and if a weed manages to poke through, it's easier to pull it out when rooted in a layer of mulch than in the soil.
• Preserves soil moisture by reducing evaporation, and helps prevent erosion caused by rain and wind. Bare soil often gets a crust on it that prevents rain from penetrating easily.
• Keeps soil temperatures cool in summer and helps to reduce the risk of damage to plant roots in winter.
• Helps keep soil from splashing onto leaves, which keeps plants looking neater and helps prevent soil-borne fungal diseases.
• As mulch decomposes, it adds all-important organic matter to the soil and keeps the top layer of soil loose and airy.

You may have heard that mulches high in carbon — anything brown — can steal nitrogen from plants. Instead of being there for the plants, soil nitrogen gets used up by the soil micro-organisms in the process of breaking the stuff down.

But this isn't a problem if you layer wood chip or bark mulch mulches on top of your soil. Just avoid mixing them into the soil.

Some people add fertilizer to make up for any nitrogen used to break down mulches. I rarely bother with added fertilizer. I garden in rich clay loam, which seems to grow plants just fine without it.