7 Creative Ways to Use Pistachio Shells in the Garden

Whether you’re growing pistachios for their nutritious nuts or snacking on them for the same reason (plus their deliciousness), there’s a question of what to do with all those woody shells. You’ve hand-opened all the little fruits, and potentially spent a healthy sum on them, and now your hard work can go to further use. Interestingly, pistachio shells have multiple applications in the landscape. 

Pistachio trees (Pistacia vera) are native to the Middle East and Central Asia, where summers are hot and dry and winters are cool and wet. The two-halved shell that holds the nuts naturally splits open during the ripening process, making them easy to access. In nature, the shells return to the soil after protecting the seed.

Technically, the shells are made of triglycerides and cellulose (fats and carbohydrates, respectively) with a layered, porous structure. As an organic material, they serve various uses, including repurposed roles in the garden.

Salted or Unsalted?

If your shells are unsalted, they can go right to the garden. If they’re salted, give them a rinse to wash away residue. Rinsing the salt keeps the mineral from building up in the soil and affecting or burning the roots. The salt may also be attractive to critters.

Mulch

Mulch is one of the easiest ways to repurpose pistachio shells in the garden. Layer the shells if you have a bunch, or add them to bark, leaf mulch, or leaf mold. They become a natural weed suppressant and boost moisture retention. They help insulate roots and regulate soil temperatures, cooling in summer and warming in winter. 

The hulls break down slowly, making them a lasting cover. As they do, they add nutrients to the soil.

Compost

Pistachio shells are dense and can take a year or more to break down; They fit the compost bin as a “brown” material. While they break down slowly, the fibrous seed coverings add nutrients as they do. As husks in compost, they help improve soil aeration. This is especially useful in heavy compositions like clay. They also increase moisture retention, a good measure for sandy soils.

To give the shells a head start on decomposition, soak them overnight before adding them to the pile. Or, crush the shells into smaller pieces for faster breakdown and easy incorporation. Don’t incorporate a huge amount into the pile, as the lack of decomposition can hamper humus development. Keep them at no more than a half gallon per 64 gallon volume of compost.

Balance the browns with greens to foster healthy microbes for a clean, earthy result. Browns are carbon-rich and include straw, dried leaves, plant material, and paper. Greens are high in nitrogen and include kitchen scraps (non-meat or dairy), grass clippings, animal manure, coffee grounds, and vegetation. 

A balanced system has more browns than greens. Maintain about three to four times more browns to avoid a smelly pile.

With regular aeration (turning and flipping) and consistent moisture, the compost contributes to healthy soils. Adding pistachio shells helps bulk up the material, making it go further.

Carrier for Repellant

As fibrous, woody structures, pistachio shells become carriers for essential oils and liquid repellents. The shells absorb the liquid’s flavor and fragrance and make for easy scattering. To repel mammals from particular garden areas and perimeters, coat shells with an organic repellent formulated for deer, rabbits, raccoons, etc. Or, moisten the shells and shake them with cayenne pepper for a distasteful effect. It’s not a science, but it works to vary traditional repellent methods.

Use them in concentrated batches around a bed or in a ring to form an aromatic deterrent. You can also place them across the soil surface of a potted specimen you want to protect. 

Pistachio shells in the garden also create an unappealing physical barrier, making it more difficult to dig and infiltrate. Placing them around individual plants or in a layered perimeter may help ward off slugs and snails who won’t want to crawl across the sharp, unstable surfaces.

Filler in Pots and Raised Beds

Pistachio shells make a useful filler material for the bottom of containers. If you have extra space in the pot and don’t need all the soil volume, they become a lightweight infill substrate. They also improve drainage as water infiltrates the soil, permeates the nutshell layer, and runs through the drainage holes.

Scatter or layer them at the base of raised beds, too, as an inexpensive filler and to suppress weeds while supporting drainage. Mix them with other organic materials like twigs, soil, and compost as the bottom bed layer.

Infill Walkways and Low Spots

Because of their durability and structure, you can use the shells to layer a walkway as you would gravel. Crush shells for placing around stepping stones or along the path’s surface. They serve as a permeable material that allows water to flow and nourish the site as they degrade. They make a great do-it-yourself path option.

The same holds for low spots or holes that need a fill material. Toss them in to help build an area that needs raising. Combine them with other organic materials for heft and further enrichment.

Aromatherapy

Bring the garden inside with a potpourri of lavender, patchouli, roses, mint, and more. Add pistachio shells to hold the fragrance. Just as they’re carriers for repellent formulas, they also absorb essential oils we welcome indoors and out. 

Use a few drops of your favorite oil on the shells, giving them a shake or stir before adding them to potpourri or placing them in a dish.

Feed the Firepit

The fibrous hulls are flammable and become kindling when enjoying chilly evenings in the garden fireside. Because of their sugars and structure, they have the capacity to pop. Bundle them in a paper bag to contain the fibers, for longer burning, and to help ignite the fire. Use only a handful at a time, as too much will cause flying sparks.