It's easy to worry about the stock market. Valuations have soared. The economy isn't out of the woods yet. Inflation remains higher than anyone would prefer. China's economic growth is stalling.

With all of that in mind, you could be reluctant to make any moves. However, even cautious investors can find some attractive picks. Here are two spectacular growth stocks you can buy in September without any hesitation.

1. D.R. Horton

You might say that D.R. Horton (DHI 0.78%) has received Warren Buffett's seal of approval in a volatile market. The legendary investor isn't buying many stocks these days. But in the second quarter of 2023, he initiated a new major position for Berkshire Hathaway in D.R. Horton.

Just because Buffett likes a given stock doesn't mean that you should like it, too. It's important to understand why the Oracle of Omaha likes D.R. Horton, though.

The U.S. continues to experience a housing shortage. There are different estimates of exactly how severe the shortage is, but most experts agree the problem is real. 

The demand for housing isn't going to decline. That means the only solution is to build more houses. As the nation's largest homebuilder for more than two decades, D.R. Horton should have a huge opportunity to help address the housing shortage. 

Importantly, D.R. Horton doesn't just specialize in one segment of the homebuilding market. The company constructs starter to luxury single-family homes as well as multi-family buildings. 

D.R. Horton stock has been a solid winner so far this year, jumping more than 30%. It's still a bargain, though, with shares trading at a forward earnings multiple of around 9.5x. 

2. Vertex Pharmaceuticals

Vertex Pharmaceuticals (VRTX -0.06%) hasn't risen quite as much in 2023 as D.R. Horton has. However, it's important to put the big biotech's 20% year-to-date gain into context. Vertex stock also soared more than 30% last year while the overall market sank.

Context is also key when it comes to Vertex's valuation. At first glance, the stock's forward price-to-earnings ratio of 25x might not seem overly appealing. But that metric doesn't fully factor in Vertex's growth prospects. Its price-to-earnings-to-growth (PEG) ratio, which projects earnings growth over the next five years, stands at 0.56 -- an exceptionally attractive level.

Part of this growth will come from Vertex's cystic fibrosis (CF) franchise which has been the key to the company's success thus far. Although the company enjoys a monopoly in treating the underlying cause of CF, it still has plenty of growth potential in reaching younger age groups and securing additional reimbursement deals. Vertex could also be on track to file for regulatory approvals in 2024 for its most powerful and potentially most profitable CF therapy yet. 

However, the company has an even greater growth opportunity expanding beyond CF. The first key step in moving into new indications is already underway. Vertex and its partner, CRISPR Therapeutics, hope to win U.S. regulatory approvals for exa-cel in treating (actually, curing) rare blood disorders sickle cell disease and transfusion-dependent beta-thalassemia by Dec. 8, 2023, for the former indication and March 30, 2024, for the latter. 

Another new product could be on the way soon, too. Vertex expects to complete phase 3 testing of VX-548 in treating acute pain by the end of 2023. The non-opioid therapy could have tremendous market potential as an alternative to highly addictive opioid drugs. 

That's not all, though. Vertex is evaluating inaxaplin in a phase 2/3 study targeting APOL1-mediated kidney disease. This indication affects 100,000 patients in the U.S. and Europe, a bigger patient population than CF has. 

In addition to all of these promising candidates, Vertex is advancing programs in earlier-stage testing that hold the potential to cure type 1 diabetes. It could be a few years before we know if these therapies will be safe and effective. However, Vertex could very well have its biggest future moneymaker waiting in the wings.