Organic Black King Mushroom Grow Kit Fruiting Block

1-Pack
$29.99

Our Certified Organic mushroom fruiting blocks make growing your own mushrooms easy. Designed by mycologists and colonized to the perfect level, all you have to do is create the right environment and fruit your mushrooms.

Pack Size

discount-eligible

all

discount-eligible-manual-with-exclusions

mushroom-fruiting-block-kits

grow-kits

shop-by-skill-level

In Stock. Ships in 2-5 business days.

USDA Certified Organic

USDA Certified Organic

Trusted by 350K+ Growers

Trusted by 350K+ Growers

Money Back Guarantee

Money Back Guarantee

Bring hearty, restaurant-worthy mushrooms to your indoor growing space. The Organic Black King Mushroom Grow Kit Fruiting Block contains a fully colonized substrate block prepared for fruiting, making it an accessible way for intermediate growers to cultivate Pleurotus spp. at home.

Black King mushrooms are a robust hybrid strain known for substantial fruit bodies and a dense, succulent texture. As they mature, expect thick stems and compact caps with a savory flavor that stands up beautifully to roasting, grilling, sautéing, and other high-heat preparations.

This Fruiting Block Kit is intended for indoor cultivation, where temperature, humidity, light, and fresh air can be monitored more closely. Place the block in a clean location with indirect light and follow the included care guidance for misting and fruiting conditions.

With proper care, the block may produce multiple flushes. The first harvest typically yields approximately 0.5–2 pounds, depending on growing conditions and the block’s performance.

Because Black King mushrooms benefit from attentive environmental management, this kit is rated Intermediate. It is a practical choice for growers ready to build on foundational experience while exploring a distinctive oyster mushroom variety.

North Spore fruiting blocks are produced with quality and cultivation reliability in mind by a mycologist-led mushroom company. Harvest when the caps are well formed and enjoy the fresh, meaty character of mushrooms grown in your own indoor setup.

Receiving and Storage

Remove kit from the shipping box as soon as possible. Then, unfold the top of the bag, making room for air space. It's also important to check and confirm that the filter patch is not obstructed. This will help the organism breathe and continue to thrive!

Fruiting blocks should be used within 1 week of receipt. If you don't plan to use immediately, you can refrigerate your block for up to 6 months.

Growing Instructions

For the majority of mushroom species, all that is needed to initiate fruiting (or begin the growth cycle) is a change in environmental conditions -- specifically humidity, light, temperature, and changes to oxygen and CO2 levels.

For best results:

We recommend growing your black king block in a fruiting chamber (like a monotub or martha tent) as a controlled environment will decrease the risk of contamination and increase the chances of success. 

Creating optimal conditions:

The environmental parameters for black king mushrooms can be found on this page under "Temp, Humidity & CO2 guide" and on page 10 of our fruiting block instruction booklet.

Preparing your block:

Unfold the top of the bag, making room for air space. It's also important to check and confirm that the filter patch is not obstructed.

How to initiate fruiting:

  • Place the bagged block in the refrigerator for approximately eight hours.
  • Make a small cut (2-3") at the top of the bag under the seam and place upright in your fruiting chamber.
  • Allow the block to pin within the bag.
  • Once pins are about 2” tall, cut off the top of the bag just under the top seam.
  • Return to fruiting chamber until ready to harvest.

Special considerations:

  • Black king mushrooms are slow to pin.
  • If you notice blotch on your black king mushrooms (dark spots on the fruiting bodies) excess humidity or direct moisture is likely the cause.

Harvesting your mushrooms:

Black king mushrooms are best harvested right before the caps flatten out. Good shelf life.

Growing different blocks together:

With some compromise, many different species of mushrooms can be grown together in a fruiting chamber. First, consider the temperature range of the mushrooms you desire to grow, and second, the CO2 sensitivity. Humidity ranges overlap for the majority of species. We encourage you to experiment with many different groupings!

Troubleshooting:

Having issues with unusual growth, stunted growth, or no growth at all? Refer to pages 16-18 in our fruiting block instruction booklet.

Temp, Humidity, & C02 Guide

Temperature 55-70°F  |  13-21°C
Humidity (Phase 1: Primordia)90-95%
Humidity (Phase 2: Fruitbody)80-90%
CO2 Sensitivity (Phase 1: Primordia)<800 ppm
CO2 Sensitivity (Phase 2: Fruitbody)<800 ppm

  • Primordia -  The earliest recognizable stage of fruitbody development. Also known as “baby mushrooms” or “mushroom pins.”
  • Fruitbody - A fully grown mushroom, the reproductive structure of the organism in which the spores are produced.
  • CO2 sensitivity - When CO2 levels are too high, yields will decrease, stems will become long and stringy, caps will be small, and/or growth will halt.

Related Articles

Upgrade Your Grow
&quot;Boomr Bin&quot; Monotub
"Boomr Bin" Monotub (+$29.99)

The best grow chamber for bulk substrate

Automated Monotub
Automated Monotub (+$149.99)

An ideal growing chamber for 1-2 fruiting blocks

Opinel No. 8 Mushroom Knife
Opinel No. 8 Mushroom Knife (+$38.00)

Harvest precisely

Wine Cap Garden Bed Kit
Wine Cap Garden Bed Kit (+$44.99)

Try growing outdoors

Boom Room II
Boom Room II (+$479.00)

The best growing chamber for 4+ blocks

Frequently Asked Questions

Fruiting block kits are mushroom grow kits, but tend to be larger (5 lbs) and some require a bit more care depending on species. Instead of boxes, they are bagged. We recommend growing them in a fruiting chamber such as a monotub or martha tent set up like our BoomRoom. A controlled environment will produce the best results for the fruiting blocks. And, since these kits are slightly larger, they can produce more mushrooms than our Spray & Grow Kits.

Oyster mushrooms and lion's mane mushroom fruiting block kits are great for beginners because they are reliable producers and require the least amount of effort. Reishi is also great because the mushroom grows in the unopened bag (no special care or fruiting chamber required!)

All kits should grow a minimum of one flush of mushrooms, but with a little patience and skill you can often get a second or third flush depending on the species! After you’ve harvested your first flush of mushrooms, remove any growth from the block and follow these instructions:

⮕ If you have a martha tent or an automated fruiting chamber, leave the humidity and fan running and wait about 2 weeks for new pins to begin forming.

⮕ If you are using a monotub or non-autmated fruiting chamber, open 2x daily and spray blocks generously with water. Try not to expose the blocks for too long to decrease chances of contamination.

⮕ If you don't have a monotub, martha tent, or fruiting chamber cover the block with a humidity tent made from a large plastic grocery bag with LOTS of small, quarter-sized holes. Remove the humidity tent 2x daily and spray blocks generously with water.

Be patient: It's totally normal for it to take longer for mushrooms to appear with each subsequent fruiting. However, if there's no progress after two weeks, it’s a good idea to soak your block.

Soaking your block: Take your block out of the bag and soak in a bowl of cool water. Most species only need to soak for 20 minutes. However, only soak your lion's mane block for 5-10 minutes as these blocks tend to break apart if soaked for too long. After soaking, let the block drain by leaving it cut side down for another 10 minutes or tip it around to let extra water run off. You don't want to leave standing water in your bag, so pat your block dry with a towel before placing it back in the bag.

Note: Shiitake blocks should not be placed back in the bag.

For most species, you should leave the block in the bag for the entire duration of the growing cycle. However, there are some exceptions.

⮕ Shiitake should be removed from the bag before going into the fruiting chamber.

⮕ Nameko should have most of the top of the bag cut off (leaving about 4" of plastic above the block) before going into the fruiting chamber.

Our fruiting block kits are made from sawdust blocks that have been amended with substrate supplements.

Cluster of brown-capped mushrooms with long, light-colored stems against a white background.

Backed by Our 100% Grow Guarantee

Every kit comes with our 100% Guarantee: You’ll get your first flush of mushrooms, or we’ll make it right. With over 350,000 happy growers, North Spore is trusted by hobbyists, chefs, and mycologists alike.

Reviews

  • 5 stars: 18 (100%)
  • 4 stars: 0 (0%)
  • 3 stars: 0 (0%)
  • 2 stars: 0 (0%)
  • 1 star: 0 (0%)
J
John B
Can't Wait

So far so good. A little slow to pin, but they're coming along. I look forward to tasting these bad boys when they're ready. Another first for me as I've never had these in a meal before.

N
Nathan Vasquez
Great mushrooms

Beautiful and meaty mushrooms!! Looks very them in spegetti sauce!

Thanks for the great review, Nathan! We're so glad you are enjoying the Black Kings! Please reach out if you ever need anything.

A
ANTOINE BAKHOS
Great experience

I was very happy with the fruiting block I have received it didnt have any issues with colonization and or contamination was very healthy mycelium block. It does take a while for the fruiting bodies to grow in my boomrbin it took a full total of 5 weeks from colonization to fruiting bodies will most definitely buy again.

Thanks for the great review, Summer! We appreciate you taking the time to share your experience. Happy to hear you enjoyed your Black King Mushroom block!

S
Summer Blackwell

The order delivery was great got it fully colonies and fruiting with zero contamination will definitely buy another fruiting block from this company... it took alot of patience growing it took about 5 weeks all togather to have it colonies and fruiting.

Thanks for sharing your experience, Summer! Black Kings can be a bit slow to grow so they will test your patience, but glad to hear the wait was worth it! The team is here if you ever need anything!

M
Maxwell Weaver
Delicious and Reliable!

I had a great experience growing this block in my automated monotub! It was a bit of a slow start as the pins never seemed to get any bigger, and suddenly they sprouted to life and grew to full maturity very quickly after a week and a half of quietness. Produced a very large flush on the first go around, but I didn't have the time to do the subsequent fruits and it got contaminated while in storage. (My own fault)

Thanks for sharing, Maxwell! These look great!

L
Lisa G
Giant Black Kings

Purchased a Black King fruiting block to grow in my monotub. They grew large stems with smaller than expected caps, so I reached out to North Spore for input. They said I needed to increase the airflow and when I did, the caps grew bigger fast. They came out great!

So glad we could help with your grow, Lisa! We are always here to help if you ever need anything!

A
Andy

Package arrived in excellent condition, the fruit block is healthy and very viable.

Thanks for sharing, Andy! If you need help with anything, please reach out.

J
Justin
So far so good

So far it’s been a pleasant experience

Best of luck with your grow! We'll be here in case anything comes up.

C
Carl

Just started but happy with everything

C
Cory Ahrens
Great product

Great product, exactly what you would expect.

P
Pete H.
Slower than others, but worth it

Very meaty, have been using them with buffalo sauce as bit of a wing substitute

R
Roger

Pretty good so far.

B
Brian Kelly Wilkins

So far so good

A
Anonymous
Delicious

Nice pins sets, good yield delicious flavor and beautiful.

W
Wes Dean
Great Mushrooms!

This block was overall very impressive and actually outperformed our other blocks we purchased. Possibly due to being in colder Colorado climate where my grow room is upper 50s lower 60s. Delicious tasting mushrooms!

D
Dylan

Excellent

C
Cayla Cameron
Slow to grow but worth it!

I got my kit six weeks ago, possibly longer and kept it in my grow tent set up with adequate lighting and humidity. I thought it was going to be a dud when I did not see any pins or change at all to the block. My mistake probably was cutting the bag open upon receiving it. However, they did grow. They are HUGE! I have never had any issue will northspore and will be a customer FOR LIFE!

J
James Lingenfelser
WOW!

I have only been growing mushrooms less than a year, so I'm still a novice. I ordered the Black King fruiting block, and as per instructions, didn't open the bag until I saw pins appear. This took 15 days(I do have poor sight), and when I opened the bag I decided to make a photo diary. the first photo taken 24 hours after opening the bag, and every morning after that until harvest. A total of 21 days from doorstep to dinner plate! I have been gardening for over 60 years and have never received such a quick return.
I love doing business with North Spore, and their customer service team can't be beat. This was the first time I had ever eaten the black king, but it definitely will not be the last!