Question
I have a LARGE amount of pine needles that I must dispose of,so I was wondering if I could use them as a mulch in my flower beds or would they create too much acid and kill my plants off? The needles are brown so I'm assuming that they are dead.

Answer
This should be an easy question to answer.  Numerous authorities use Pine Needles to mulch around the garden.  The American Rose Society applies them by the truckload to specimens at their official Rose Garden in Greenwood, Louisiana.  Pine Needles are TREASURED in some Southern communities on a level beyond comprehension -- one exclusive Texas neighborhood is said to truck them in from Georgia, according to claims by the Villager Nursery, a California garden center that pushes Pine Needles as a first rate option to be used by the pickiest gardeners.  Villager Nursery maintains the pH of Pine is not the strong Acidic amendment some people think it is; it typically tests, they say, around 6.5 -- an ideal pH for most plants.  Read all about it on the Villager website:

http://www.villagernursery.com/Reference/Articles/Pine_Needle_Compost.doc

So, then, what's not to like about Pine Needle Mulch?

Ever hear of Terpenes?

We get the word 慣urpentine?from this word.  Botanists pay attention to Terpenes because they can interfere with the germination and growth of new plants.  Wikipedia explains it like this:

'Terpenes are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers...'  Coincidentally, Wiki illustrates their point with a Pinetree (the caption: 'Many Terpenes are derived from conifer resins, here a Pine.').  Terpenes are what you smell when you put up a Christmas Tree.  They are highly flammable and intensify fires in Pine Forests.

Terpenes and related Monoterpenes and Terpenoids are also strong chemicals.  One internet-posted Bio 101 text (www.biosbcc.net/b100plant/) explains how they work:

慣hese volatile or water-soluble chemicals are ...carried by the heat of the day or by water to the soil. The allelopathic agents may also leach out of the leaves or leaf litter to accumulate in the soil beneath. These compounds effectively stunt the growth of plants and reduce or eliminate seed germination. Allelopathy is a plant defensive mechanism. It ensures the limited moisture and nutrients available in the soil are only capable of being used by the plant producing the allelopathic chemicals...?br>
I don't know about you, Sandy, but when I read that something screws up Seed germination or companion plant growth, I get nervous.

So, since I was nervous, I started reading up on Terpenes and their friends, to see what current research might contribute to getting rid of my Tylenol Headache.  I just kept finding study after study that seemed to say that Terpenes come from Pines, and are bad for neighboring vegetation.  Colorado State's Entomology Dept issued a cheat sheet on Terpenes a while back: 'Monoterpenes are major constituents of many Pine Resin Oils...Monoterpenes have been found to have antimicrobial activities ... As allelopathic agents, they are also thought to inhibit plant growth and germination in several plant communities...'

But there was also some good news.

You see, Pine Needles produce a Fungally dominated Compost for mulching.  This is the GREAT PREFERRED amendment of Trees, Shrubs, and most Perennials.

So, what is the bottom line here?  Can you use them in your flower bed, or not?

OK, It is my understanding that Terpenes and their volatile cousins are short-lived.  They dissolve in water or dissipate in the air, leaving behind enough of a trace to discourage microbes and support Fungal growth.

Besides, an entire section of the country can't be completely wrong about this.  Dixie LOVES Mulch of Pine.

By the time those Pine Needles are Brown and Dry, there are few if any Terpenoids to play with, smell, taste or otherwise repel vegetation in a flower bed.  To be on the safe side, I would make sure the Needles no longer exude that lovely Pine fragrance when you buy the Mulch.  Watch your plants to see how they take to this mulch.  It is worth trying, definitely; it is probably not only safe, but excellent; and it is free.  You know that old gardener's saying: The BEST things in life are free.

Thanks for writing, and I'm sorry this took a year and a day to answer; I was, as I said, somewhat alarmed by the things I was hearing.  Pine power.