What is the Solo Cup Challenge? (Grow Weed in a Cup)

Published Jun 24, 2021

by Nebula Haze

Why grow cannabis plants in solo cups? It’s a silly and captivating project for any cannabis grower who wants some fun on the side and a little bonus weed.

The Solo Cup Challenge

  • Grow a weed plant from beginning to end in a solo cup or other small cup
  • See which plant looks the most impressive or gets the best yields

Check out the solo cup challenge post in our forum for tons of amazing examples!

Why It’s Hard

  • Plant roots get unhappy when constricted and solo cup plants may get rootbound and die.
  • You have to give absolutely optimal conditions because the plant is not resilient to problems
  • Can be difficult to water plants often enough as they get bigger. Some growers must water plants multiple times a day either by hand or with a drip feed so they don’t dry out.
  • Can be difficult to balance plants due to the tippy nature of cups

There’s no real reason to grow this way… but it’s so fun! Here are some examples. Send us your solo cup challenge pictures for a chance to be featured on this page.



Here’s my first attempt at the solo cup challenge, circa 2010. All of these plants were given a 12/12 light schedule from seed to get them to start flowering (making buds) as soon as possible.

One seedling did not make it lol. This was the result of heat plus overwatering.

I learned and this one did much better

This weed plant in a solo cup is already way to big and should be transplanted to a bigger pot ASAP

Definitely not the healthiest leaves at harvest, but it produced 0.75 oz of premium bud under a handful of CFL bulbs!

Then I forgot about the solo cup challenge for many years…



These plants from 2020 weren’t part of a real solo cup challenge. Basically I sprouted some extra auto-flowering seeds and although I picked the winners for my bigger tent, didn’t want to toss these little ones. So I just kept watering them in their cups and let them do their thing. I stuck them in my bonsai mom tent where they shared an 85W LED in a 2’x2′ with several other small plants. They still flowered and made buds because they are auto-flowering strains. I think auto-flowering strains make it so much easier to do to the solo cup challenge.

They all tended to stay small because their roots were constricted

Here’s how they turned out!

Zkittles Auto

Alaskan Purple Auto

White Widow Max Auto

None of these plants would win any solo cup challenge, but they made the cutest harvest ever out of some random extra plants

I got over an ounce from these little “trash plants” 🙂

Here were some of their brethren that were germinated at the same time but put in normal plant pots and given access to a real grow light. Look what happens when you give cannabis plants room for their roots to grow!

A cool thing about autoflowering strains is you can stick a solo cup challenge almost anywhere since these strains don’t care about light schedules. I snuck two solo cup plants in the upper corners of this tent for about an extra ounce of buds out of no where.


I grew this autoflowering plant in a sunny window.  I used a little container of soil to give the plant stability and hold extra water (I cut out the bottom of the cup so the roots could spread out a bit), so I’m not sure this counts as a real “solo cup challenge”. But I wanted an excuse to post a picture of my cat 🙂

Solos cup cannabis plant growing with a hungry cat thinking about taking a nibble. This plant was auto-flowering so it can be left in a sunny window.

After drying it was 3.5 grams (1/8 oz) of premium bud. Not the biggest harvest but free since it was in a window and definitely one of the most fun grows I’ve done!



I think this may be one of the cutest entries so far. Not fair to use baby bunnies! 🙂 ~Nebula

Here’s a few solo cup pics and a couple off-topic pictures to brighten your day.

I didn’t intentionally grow in solo cups, these were just the tops of manifolded plants (Mimosa EVO) that I couldn’t bring myself to toss. I snipped them and stuck them straight in a cup of coco with no extra love or rooting gel, put them off to the side out of direct light and watered them with the leftovers from my full size plants, otherwise pretty much ignoring them… they couldn’t be killed! They don’t call it a weed for nothing. They were so top-heavy the fan would blow them over when they needed watering. Not a huge harvest but some small, dense, generally respectable nugs I wouldn’t otherwise have had.

The off-topic pics are a litter of bunnies that momma had in a planter pot a week ago (sadly just a rosemary plant) right outside my back door. So much for letting my dog run around in the back yard for a few weeks while they grow up enough to leave the warren🙂 (he is a type that was bred to hunt rabbits and small game and can’t be let anywhere near them). Apparently rabbits have babies in yards with dogs to keep other predators away, but they picked my yard with a dog that specializes in catching rabbits. Slight miscalculation but they were lucky we saw them before he did (unlike last year).


Great site!


P.S. And who doesn’t like bunnies! (pics taken with a zoom and they were left undisturbed so there wouldn’t be a risk momma would reject them)

Thanks for sending this in, these little bunnies are enchanting! ~Nebula



Here’s another solo cup plant that was sent in by a grower, no name attached. ~Nebula

At harvest

Those roots pooled down at the bottom and had nowhere to go



Got a solo cup plant you want to share with the world? Send us your solo cup challenge pictures for a chance to be featured on this page!



Return to Top of Page