North Spore Spray-and-Grow Kit Review: Honest Results After 3 Flushes
I grew up thinking mushroom kits were a gimmick. You spend $30, spray water twice a day for two weeks, get a small handful of mushrooms, and that is it. Most reviews prove me right because they document exactly that: one flush, a decent photo, and a verdict of ‘yeah it worked.’
What those reviews skip is everything that happens next. The yield drops. The block dries out if you are not careful. And the math changes.
I ran North Spore’s Blue Oyster Spray and Grow kit through three full flushes, tracked wet-weight yields on a kitchen scale, and did the cost-per-pound math at each stage. Here is what I found.
The Kit: What You Get for $29.99
The North Spore Organic Blue Oyster Spray and Grow Kit sells for $29.99. It ships as a 4 lb block of organic wheat bran and sawdust, fully colonized with Pleurotus ostreatus mycelium. The block measures 10 inches tall, 5 inches wide, and 5 inches deep. It arrives wrapped in a perforated plastic bag with a filter-paper patch on one face that you cut open to expose the fruiting surface.
That is it. No spray bottle included, despite what some listings suggest. No tent. No humidity gauge. You supply those yourself.
USDA certified organic, made in Maine, non-GMO. North Spore backs the first flush with a guarantee: if nothing fruits, they replace it. I have never had to test that guarantee.
Setup: About 10 Minutes of Work
Refrigerate the kit when it arrives if you are not starting it immediately. Shelf life is around 6 months cold. When you are ready, pull it out, cut the X on the filter patch, fold the bag back, and start misting the exposed surface twice a day.
Temperature matters more than most beginners expect. Blue oysters fruit best between 55 and 65F. In a house kept at 70F they fruit slower and pin less densely. I learned this on my first kit and did not repeat the mistake. For this review I moved the block to a basement space sitting at about 62F. That single change made a real difference in pin density.
Humidity should stay above 80% at the fruiting surface. Misting twice daily handles it in most climates. If you live somewhere dry, a plastic storage bin with holes drilled in it works as a cheap humidity tent and costs under $10 at any hardware store.
Flush 1: Days 3 to 14
Three days after cutting the bag open, I saw pins. Tiny gray nubs clustered across the entire face of the block. By day 8 they had grown into full caps with visible gills. I harvested at day 14 when the caps were spreading wide but still firm, just before the edges started to wave and curl. Waiting past that point means lower quality and faster spoilage.
Wet-weight yield: 21 oz (1.31 lbs)
That is a solid first flush. The mushrooms were dense and meaty, and the batch sauteed down beautifully with butter, garlic, and a pinch of salt. Nothing subtle about the flavor.
At $29.99 for 21 oz, the cost per pound after flush 1 comes to $22.85/lb.
That is expensive. More expensive than Whole Foods oyster mushrooms, and more expensive than the $12 per pound you would pay at a specialty grocer. This is the number that every one-flush review conveniently glosses over.
Flush 2: The Recovery Period
After harvest, I scraped the cut surface lightly to remove any remaining stubs, gave it a good misting, and moved it back to a dark shelf for 5 days. This rest period allows the mycelium to recover and push nutrients toward the next fruiting layer.
Pins appeared on day 6 of the rest period. The second flush always fruits faster than the first because the mycelium knows what to do. By day 11 I had a full second cluster, smaller in diameter but structurally solid.
Wet-weight yield: 11 oz (0.69 lbs)
Expected. The second flush typically runs 40 to 60% of the first. With optimal temperature and humidity you can pull nearly equal second flushes, but at normal home conditions, plan on roughly half.
Running total: 32 oz (2.0 lbs). Cost per pound: $15.00/lb.
Now we are in grocery store territory. Organic blue oyster mushrooms at a farmers market or specialty grocer in most U.S. cities run $10 to $15 per pound. After two flushes, this kit sits at the high end of that range.
Flush 3: Diminishing Returns, But Still Mushrooms
By this point the block was visibly lighter and had brown patches on the exposed surface. That is normal. The mycelium is aging and the substrate is running low on available nutrients.
I gave it a full 7-day rest, kept humidity slightly higher than before, and waited.
Pins appeared on day 8. The cluster was much smaller than flush 2, but it was real and harvestable.
Wet-weight yield: 6 oz (0.37 lbs)
Running total: 38 oz (2.38 lbs). Cost per pound: $12.63/lb.
At $12.63 per pound over 3 flushes, you are now below the $14 to $15 per pound price for fresh organic blue oyster mushrooms at most specialty stores. You have passed the value threshold against premium retail pricing.
You have not beaten a discount grocery selling gray oysters at $6 per pound. But that was never the comparison that made sense here.
The Cost-Per-Pound Math, Laid Out
| Flush | Yield | Cumulative | Cost/lb |
|——-|——-|————|———|
| 1 | 1.31 lbs | 1.31 lbs | $22.85 |
| 2 | 0.69 lbs | 2.00 lbs | $15.00 |
| 3 | 0.37 lbs | 2.38 lbs | $12.63 |
The breakeven against premium organic pricing lands somewhere during flush 3. If your conditions run better than mine and you pull a 1.5 lb first flush, you will hit that crossover point earlier.
If your first flush comes in at 10 oz due to dry air or high room temperature, the math never gets comfortable. Environment is the variable this kit cannot control for you.
What About the Pink Oyster Kit?
North Spore also sells an Organic Pink Oyster Spray and Grow Kit at the same $29.99 price and identical 4 lb block dimensions (10 x 5 x 5 inches). Pink oysters (Pleurotus djamor) are a tropical species, and that changes things.
They fruit at 70 to 85F, which means no cool basement required. If you keep a warm house or live somewhere hot, pink oysters are genuinely easier to start than blue. They pin faster too, often within 2 to 3 days in ideal conditions.
The tradeoffs: pink oysters are more sensitive to humidity swings, and their shelf life after harvest is short. Within 48 hours at room temperature they start to degrade. You need to cook them or refrigerate them the same day. The flavor is excellent, described by most people as slightly sweet with a savory, ham-like edge, but freshness is not optional.
For cumulative yield potential across 3 flushes, pink oysters are comparable to blue. Some growers report slightly higher first-flush yields from pink kits because of faster colonization speed, but I would not count on it. Plan for similar numbers.
Rule of thumb: cool space (55 to 65F)? Go with the Blue Oyster. Warm house or tropical climate? The Pink Oyster kit fits your environment and you will have less friction getting it to fruit.
Who Should Buy This Kit
The North Spore Spray and Grow kit earns its $29.99 if:
- You already spend $12 to $15 per pound on specialty or organic mushrooms
- You want same-day fresh mushrooms without a trip across town
- You find the growing process itself enjoyable, not just a means to food
Skip it if:
- You expect it to replace $6 per pound grocery store mushrooms economically
- You want to scale into commercial growing (you need fruiting blocks or colonized bags for that)
- You cannot commit to 2 minutes per day of misting
This kit is not a money-saving tool for the average mushroom buyer. It is a value-for-money tool if you are already buying in the specialty mushroom market, and it delivers a fresher product than anything that has been in refrigerated transit for three days.
My Recommendation
Buy the North Spore Blue Oyster Spray and Grow Kit ($29.99, 4 lbs, USDA organic) if you have a cool space that stays around 60F and you are already paying specialty store prices for oyster mushrooms.
Run all three flushes. That is where the math works. Stopping at flush 1 means you paid $22.85 per pound for gourmet mushrooms. Finishing flush 3 brings that down to $12.63 per pound, which is competitive with what most specialty stores charge.
For warm-house growers who cannot consistently hit that 55 to 65F window, the Pink Oyster kit at the same price is the better fit and will fruit faster with less effort.
Do not stop at flush 1. That is where the value has been hiding the whole time.