Yes, you can grow walnut tree from store-bought nut as long as that nut is raw, unprocessed, and still in its hard outer shell. The embryo inside must be alive and intact for it to sprout. This means you need to be picky about which walnuts you buy if growing a tree is your goal.
Your store-bought walnut germination rate depends on where you buy your nuts and how they were handled before reaching the shelf. I tested batches from three different sources one winter. The in-shell raw walnuts from my local health food store gave me a 70% sprout rate after cold treatment. The bagged walnuts from a regular grocery chain gave me nothing at all. Farmers market nuts fell right in the middle at about 40% because their storage conditions varied from vendor to vendor.
Heat processing and roasting kill the tiny embryo inside every walnut they touch. Even light toasting at 300°F (149°C) for a few minutes is enough to destroy the living tissue that would become your tree. This is why you can only use raw, unprocessed nuts with their hard shells still intact. If the package says roasted, salted, flavored, or blanched, those nuts are dead and will never sprout no matter what you do with them.
Your best bet is to find walnuts sold as raw and in the shell at a health food store, a farmers market, or an online specialty seed supplier. These sellers tend to store their stock in cool, dry conditions that keep the embryo alive much longer. Walnuts that have been sitting on a warm store shelf for months lose viability fast. Ask your seller how recently they received their shipment and how they stored the nuts before putting them out for sale.
Before you commit to the cold treatment process, run a quick float test to check which nuts are still alive. Drop your walnuts into a bucket of room temperature water and wait two minutes. Nuts that sink to the bottom have dense, healthy kernels inside and are your best candidates to sprout. Nuts that float are often dried out or hollow inside, and you should toss those ones out right away.
Once you have your viable nuts sorted, wrap each one in a damp paper towel and place them in a zip-lock bag. Store that bag in your fridge at 34 to 41°F (1 to 5°C) for 90 to 120 days of cold treatment. Check your nuts every two weeks and re-dampen the towels if they feel dry. After three to four months, you should see small white root tips poking through the shell.
When you see those roots, you are ready for planting store walnuts into soil. Plant each sprouted nut 2 to 3 inches deep in a pot filled with well-draining potting mix. Keep the soil moist but not soaked, and place the pot in a warm spot with bright light. Your seedling should push through the surface within two to three weeks of planting. From that point on, you have a real walnut tree started from a nut you picked up at the store.
Read the full article: Growing Walnuts: 7 Key Steps
