Using sawdust in vegetable garden as mulch?

(Question)

I would like to get some info on using the sawdust and wood shavings on my garden this year as mulch or working into the ground in early spring. Would putting a lot of this down kill the weeds and will it feed my veggies?

As I live in the country, I will be using shavings from pine, hickory, tulip, cherry, soft maple, white ash, oak. birch and a little bit of black walnut, any suggestions?

There may also be a little sawdust from MDF.

 

(Answer)

In general, sawdust is not recommended as a mulch as it tends to leach nitrogen from the soil, making the nitrogen unavailable for plant growth. It is better to use sawdust as part of your compost. Woodchips can be used as mulch as long as they are not obtained from pressure treated wood, such as MDF, which contain chemicals.  That said, wood is an organic product. Rotted wood chips can provide organic matter that enhances the soil’s ability to retain nutrients. The key is time and adding nitrogen.

It is important to spread fresh wood chips out to let them dry, turning regularly to let the air get at them. Otherwise, they may produce substances such as methanol or ammonia which can harm plants. This ”aging” process helps the chips to break down. When they are added to the soil, consider also using a high nitrogen fertilizer such as blood meal.

Black walnut trees produce a toxin called Juglone that can infect many plants. This is present in the bark and leaves as well as the roots. The toxicity in leaves can be broken down in one or two months if they are composted separately. The bottom line is that it is safer not to use any part of this tree.

You have a fine source for wood chips and these definitely have a role to play as a mulch and additive but must be used with patience and caution. For your veggies, it is better to use compost or shredded leaves to add organic content to the soil until you are sure that you have isolated the Black Walnut and pressure treated wood chips.

Here are links to websites that explain the pros and cons of wood chips as mulch and the use of Black Walnut:

www.motherearthnews.com/organic-gardening/building-garden-soil-wood-mulch-zmaz10onzraw.aspx

http://www.torontomastergardeners.ca/index.php/factsheet/juglone-and-black-walnut-a-toronto-master-gardeners-guide/

http://ohioline.osu.edu/hyg-fact/1000/1148.html