Unlike other leaves, pine needles take a long time to decompose. I have pine trees, and the needles collect on the ground below in piles. I am always anxious about using them because I can only use so much in the compost since they don’t break down as easily or quickly as other organic materials.
Pine needles take months or even years to decompose because they have a wax coating. How fast they decompose depends on the prevailing conditions. Shredded pine needles break down more quickly than whole pine needles. Additionally, when exposed to moisture and warmth, they rot faster.
In this article, I’ll explain why pine needles take so long to decompose. I will also offer useful ideas on how to help them break down quickly so you can use them in your garden.
Why Pine Leaves Take Long to Decompose
Pine trees are evergreens, and the needles remain on the tree for years. They only fall from the tree when they age.
However, they take an equally long time to decompose. This is unlike the leaves of deciduous trees, which often fall and decay just as quickly.
Depending on the existing conditions, pine needles take weeks, months, or even years to decompose.
The slow decomposing process is due to the following reasons.
The Needles Have a Tough Exterior
The wax-like coating is the reason pine needles don’t break when you fold them. When on the tree, this wax coating traps fluids in the leaves, helping them retain their green color all year. Unfortunately, when the tree falls, this coating remains and prevents quick decomposition.
Microbes Can’t Penetrate Their Coating
Microbes, which play a crucial role in organic decomposition, cannot penetrate the tough coating on pine needles. So, while other leaves and grasses break down, pine needles remain the same until the coating starts wearing off.
Moisture Is Low
The moisture level in pine needles is low and is sealed within the cuticle. They also lose moisture slowly because they have a small surface area.
I have a holiday wreath that has some pine needles. They have remained the same for years, partly because the storage conditions do not allow them to decompose. However, it also shows the tenacity of pine needles.
If you want them to decompose quickly, you must step in and make it happen.
How to Make Pine Needles Decompose Faster
Like other leaves, pine needles can be handy in compost. They are rich in nutrients and have physical properties that keep them from losing much water and nutrients.
When they eventually break down, they will enrich the compost. The challenge is how to speed up the decaying process.
You can make pine needles decompose faster by shredding them, keeping them wet, and leaving room for aeration. You should also only add about 10% of pine needles to your compost to ensure an even and faster breakdown of the material. Pile them in small batches and keep turning them to rot faster.
Once you shred pine needles, microorganisms can start breaking them down because they now have access to the inside of the needle. This helps the pine needles to rot faster, and when you improve the composting conditions, you can use your compost in a few weeks or months.
Tips For Composting
Pine needles drop down, just like other leaves. However, you can collect leaves from deciduous trees and compost them immediately. You cannot do the same for pine needles because they don’t decay quickly.
Here are tips on how you can speed up pine needle decomposition:
Compost Separately in Small Batches
Pine needles, like other leaves, fall under brown material. The browns in compost are critical because they maintain their structure longer than the greens. They introduce oxygen and improve air circulation, which is vital for organic decomposition.
The browns also retain moisture and nutrients as they decompose.
Unfortunately, the pine needle structure is more complex than that of leaves from deciduous trees. They do not retain moisture, and the shape does little to support the compost structure. The spaces between the needles can also be compressed and compacted under the weight of compost material.
You can speed up decomposition by composting pine needles separately before adding them to other compost materials. Pile them in small piles to allow rain and sunshine to break down the needles. The coating will come off eventually, and the needles will start rotting.
Shred Them Before Composting
Bacteria and other microbes are critical in the decomposition of organic material. Unfortunately, they cannot get through the waxy coating on pine needles. When you shred the pine needles, you provide a path for the microbes to get into the pine needles and start breaking them down.
You can use something like an electric mulcher chipper that shreds leaves and branches up to around 1.75 inches (4.4 cm) thick.
Use Hot Manure
Compost naturally generates heat as it cooks. When you layer green and brown materials and let them sit, they start to generate heat because of the high nitrogen levels. You can also add hot manure to pine needles to speed up decomposition.
Fresh manures with high nitrogen concentrations include:
Hot manure is harmful when added directly to the garden. However, when you mix it with pine needles, they will break down quickly.
Add hot manure to pine needles together with other sources of carbon, such as straw. Ensure to use small quantities of pine to ensure they break down quickly.
Only Add 10% to the Compost
Since pine needles break down slowly, you shouldn’t add too much to the compost. When you add a lot of pine needles, they will stand out even if the other organic matter breaks down. This makes the compost unsuitable for use until the pine needles decay.
Pine needles should only make up 10% of the compost. This way, microbial activity remains high, and the pine needles have a better chance of losing the waxy cuticle and breaking down.
Lay Shredded Ones at the Base of the Compost
Have you noticed that pine needles at the base of a compost decay faster? Often, those at the top remain the same. This is because pine needles at the bottom are exposed to ideal decomposition conditions.
Moisture, heat, and microbial activity help to break down the pine needles faster. So when layering your compost, put the pine needles at the base before layering the other organic materials.
This video gives tips on how to compost pine needles and get the best out of them:
Avoid Composting Green Needles
Most leaves fall from the tree when they are brown. Pine trees are evergreens, and the needles only fall once they age and not necessarily when they turn brown. However, some pine trees shed needles when they start browning, especially if the tree has gone for a long time without water.
Whatever the case with the pine needles you collect, you should ensure you don’t compost green pine needles. This is because pine is acidic, with pH levels ranging from 3.2 to 3.8. However, the pH will be closer to neutral when the pine needles fall, start drying, and eventually decompose.
While the low pH is unlikely to affect compost quality, it may slow down microbial activity. Bacteria work great in compost because it is alkaline. Their movement and activities may be inhibited if you add fresh green pine to the compost, slowing decomposition even further.
When composting pine needles, it is essential to know the duration they take to break down. Sometimes they take months, but they can also take years to decay. However, you can prepare your compost with the intention of using it in the next growing season if you take measures to speed up the decomposition of your pine needles.