Can You Grow Portobellos from Store-Bought Mushrooms?

Many gardening enthusiasts and mushroom lovers often wonder if it’s possible to grow Portobello mushrooms from store-bought specimens. 

While the idea sounds practical and cost-effective, the reality is a little more complex. Let’s dive deeper into the fascinating world of mycology and explore the possibilities (and challenges) of growing Portobellos at home.

Growing Portobellos From Store-Bought Specimens

Portobello mushrooms, scientifically known as Agaricus bisporus, are increasing in popularity. As the mature form of Agaricus bisporus, Portobellos are really just mature cremini mushrooms – but they’re much larger, less water, and in our opinion, have better flavor. 

Like Cremini they are one of the many mushroom varieties that can be grown at home, but doing so from store-bought samples is not as straightforward as it might seem.

The cycle of Portobello mushrooms is delicate. It begins with spore germination on suitable substrates, leading to the growth of mycelium (the main body of the fungus that colonizes the growing medium). Under specific environmental conditions, the mycelium develops into a visible fruiting body called a mushroom, which releases spores for dispersal and initiates new cycles of germination and growth.

When you buy a Portobello mushroom from a store, it is the fruiting body of the fungus and, technically, it carries the spores — the ‘seeds’ of a mushroom. 

In theory, you could collect these spores, germinate them into mycelium, and eventually grow mushrooms. However, the process is fraught with challenges.

First, it’s crucial to understand that store-bought mushrooms are usually grown in controlled environments under very specific conditions. The mushroom you buy from the store is at the end of its life cycle, making it difficult to use as a reliable source of spores. Even if the mushroom is fresh, the spores might not be viable, or the mushroom might be a sterile hybrid that doesn’t produce spores at all. Moreover, supermarkets often store mushrooms under conditions that are not conducive to spore viability.

Secondly, even if you manage to get viable spores, the process of germinating them into mycelium is complicated and requires sterile conditions. Any contamination can hinder the growth of the mycelium and promote the growth of unwanted mold or bacteria. Thus, it requires a good understanding of mushroom biology and sterile techniques.

Preferable Methods for Growing Portobellos

A more reliable way to start your mushroom-growing adventure would be to purchase a mushroom-growing kit with spawn or liquid cultures. 

In addition to guaranteeing sterilization, this approach helps provide your mushrooms with exposure to ideal growing conditions. 

Portobello mushrooms prefer a growing medium of composted manure and straw, and they require specific temperature and humidity levels; they grow best at temperatures between 55 and 70 degrees Fahrenheit and humidity levels of around 95%.

Unlike attempting growth from store-bought spores, using a growing kit with spawn or liquid cultures ensures you hit every box on the checklist when it comes to mushroom cultivation best practices.

In approximately 3-4 weeks, you should start to see small mushrooms, known as “pins,” appearing. Over the next week, these will grow and mature into Portobello mushrooms. You’ll know they’re ready to harvest when the cap has expanded and the gills are visible.


While it’s theoretically possible to grow Portobello mushrooms from store-bought specimens, it is not the most reliable or straightforward method.

If after reading this article, you’ve decided that you’d be better off using a grow kit, we have good news!

We prepackage all materials and equipment you’ll need in our All-In-One Mushroom Grow Kit, and we also have a variety of mushroom spores available here.

We also care about making sure you have the right information before making any decisions, if you have ANY questions about our equipment, please reach out to us here.

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart
Scroll to Top