Marijuana legalization has been growing like a weed for the past two decades, but 2016 could prove to be its most monumental year yet. Although marijuana has gained 24 state approvals for medicinal use, and four states have legalized its recreational use, we could see up to 12 separate approvals for the currently illicit drug in November.

This expansion is especially important because current President Barack Obama has suggested that the best way to get the attention of Congress is to continue legalizing the drug at the state level. Doing so would eventually force lawmakers to reconsider the federal government's current Schedule 1 stance on the drug.

In total, voters in three states are guaranteed to vote on marijuana this November. Of the remaining nine states, one is a seeming lock to get a marijuana initiative on the ballot, while the remaining eight are still in the process of collecting signatures.

Three states guaranteed to vote on marijuana in November

1. Nevada
Heading into 2016, there was only state guaranteed to vote on marijuana this year, and that was Nevada. Nevada's recreational-marijuana initiative, known as Question 2, was approved for the ballot in November 2015, and it aims to make the drug legal for adults aged 21 and up. If it's approved, an excise tax of 15% would be enacted to support the state's K-12 education budget.

2. Florida
Florida's medical-marijuana initiative, known as Amendment 2, or the Florida Right to Medical Marijuana Initiative, wound up collecting nearly 693,000 signatures by late January, working its way onto the ballot once again. Medical marijuana use under the law would be limited to "debilitating" medical conditions as defined by a physician. This year's effort follows the narrow defeat of a similar medical-marijuana initiative in 2014 that saw the "yes" votes fall 2.4% short of the 60% required to pass.

3. Maine
Roughly a month ago, Maine also announced that enough signatures had been gathered to get a recreational-marijuana initiative on the ballot this November. If the initiative -- known as the Marijuana Legalization Act -- is approved, then a state excise tax of 10% would be imposed on recreational marijuana sales, and licenses within the state could be limited.

This state may as well be a lock to vote on marijuana

4. California
While it may not be guaranteed as of yet, it looks to be a near lock that California residents will vote on a recreational-marijuana initiative, known as the Adult Use of Marijuana Act, this fall. Though just 365,880 signatures were required, supporters had gathered around 600,000 as of this writing. According to Lieutenant Governor Gavin Newsom, "You can rest assured this will be on the November ballot." Given that California has the largest economy by GDP in the U.S., an approval would be a crowning victory for the movement in 2016. 

Eight states still collecting signatures

5. Arizona
Residents in Arizona could vote on a recreational marijuana initiative, known as the Legalization and Regulation of Marijuana Act, this November, assuming 150,642 signatures are collected by July 7. Based on figures from Arizonans for Mindful Regulation, around 100,000 signatures had already been collected by late February. If it's approved, a 10% tax would be imposed on recreational-marijuana sales. This could prove to be a close vote as well, with polls in April showing that the "No" votes outnumbered the "Yes" by 6 percentage points.

6. Arkansas
The Arkansas Medical Marijuana Amendment of 2016 was approved in mid-February by the state's attorney general to begin collecting signatures. In late March, Arkansans for Compassionate Care reported that more than 68,000 signatures had been collected, with 84,859 needed to get the measure on the ballot. If the amendment is approved, half of the sales tax revenue from the sale of medical marijuana would go to the state's Vocational and Technical Training Special Revenue Fund, while another 30% would head to the state's general fund. The remainder would go toward a Skills Development Fund and to the medical-marijuana program.

7. Massachusetts
The Regulation and Taxation of Marijuana Initiative in Massachusetts seeks to legalize the use of recreational marijuana. Initially, 64,750 signatures were needed, which supporters easily met. However, the legislature failed to enact the initiative, requiring supporters to collect an additional 10,792 signatures by June 22 if it's to make it onto the ballot. If approved, recreational marijuana would be taxed at the state's 6.25% rate, plus an excise tax of 3.75%. Cities and towns could also tack on up to 2% in local taxes, too.

Image source: Flickr user Cannabis Culture.

8. Michigan
In Michigan, the Marijuana Legalization Initiative needed 252,523 signatures by June 1 to make it onto the November ballot. If approved, the measure would institute up to a 10% tax on recreational marijuana and expand the statewide cultivation of industrial hemp. Recent polls have suggested a slight majority in favor of approving recreational marijuana within Michigan.

9. Missouri
The Medical Marijuana Legalization Initiative in Missouri, if approved, would legalize the use of marijuana for medical purposes and impose a 4% tax on the retail sale of medical marijuana. Proceeds from the tax revenue would be used to pay for healthcare services for military veterans and to cover the costs of administering the program. Signatures have already been submitted and are being reviewed for their validity.

10. Montana
Montana actually has multiple recreational-marijuana initiatives in the process of collecting signatures. Normally, when multiple initiatives are on the table, legislators eventually decide on just one. Marijuana Legalization Initiative I-178 would legalize the use of recreational marijuana for adults aged 21 and up and institute a 20% excise tax on retail sales, which would then be allocated to the state's General Fund. 

11. North Dakota
The Legalization of Marijuana Initiative in North Dakota is looking to legalize recreational marijuana within the state while also limiting taxation on recreational marijuana to no higher than 20%. Interestingly, this bill also proposes to prevent the state from requiring a license to grow, possess, use, or distribute marijuana. Sponsors will need to gather 13,452 signatures by July 11 to get the initiative on the November ballot.

12. Oklahoma
Lastly, the Medical Marijuana Legalization Initiative in Oklahoma is looking to legalize the licensed growth and use of medical marijuana. The measure, filed in April, mandates that supporters collect at least 65,987 signatures to get it on the November ballot. However, this could prove a tall order: Signature collection for a medical-marijuana initiative has fallen short in Oklahoma twice before.

Image source: Pictures of Money via Flickr.

Caution is still warranted

Even though we could be looking at a record-breaking year in terms of expansion for marijuana, investors who are seeing dollar signs may want to temper their expectations. Just because marijuana could gain new state-level approvals in 2016 doesn't mean the federal government will necessarily be in any hurry to change its stance. In other words, it means the marijuana industry will continue to face several big disadvantages.

For starters, marijuana businesses have minimal access to basic banking services. Most marijuana companies are struggling to get lines of credit or even checking accounts because they fear possible prosecution from the federal government down the road. If marijuana businesses are struggling to get basic financial services, then it could constrain their hiring and expansion efforts.

The other issue here is that U.S. tax code 280E forbids businesses that sell illegal substances from taking normal business deductions. This means marijuana companies can't even write off their rent expenses, causing them to pay a substantially higher tax rate than they should.

Long story short, even with marijuana expanding to new states, marijuana companies may not be poised for success. Until we see discernable changes at the federal level, I'd still advise you to avoid "marijuana stocks."