The fund, about 40 percent invested in the renewable energy industry, suffered last year when oil prices plummeted, losing 61 percent in value, nearly double the 37 percent slide in the benchmark Standard & Poor's 500 Index.
But the $60 billion slated for clean energy in Obama's stimulus bill, and a steep rally in oil prices since winter, are bolstering the fund, which invests in securities of companies committed to solving environmental problems.
"Our commitment to what we call low-cost, low-carbon renewables is paying off," Robinson, president and chief investment officer of Boston-based Winslow Management Co LLC, said in an interview.
"And frankly it's even more exciting than we thought it would be because the government is subsidizing it for some period of time in a very significant way."
The Obama administration has made transforming the way Americans use energy one of its priorities and has included in its economic stimulus packages a number of provisions supporting renewable energies such as wind and solar.
Robinson's interest in sustainability began with a book written by his parents on how to profit from home gardening during World War Two, when household gardens sprouted in response to wartime shortages. He started the firm in 1983.
Green Growth's top two equity holdings last quarter, WaterFurnace Renewable Energy Inc and LSB Industries Inc, produce geothermal heat pump systems that use the Earth to heat or cool buildings.
Shares of LSB have surged about 93 percent this year, vastly outperforming the S&P 500's 0.8 percent gain. By some measures, the stock still looks cheap, trading at roughly 13 times projected 2009 earnings, slightly below its peers.
WaterFurnace has gained about 9 percent this year, but looks a little more expensive, trading at about 21 times 2009 earnings, according to Reuters Estimates.
The fund also invests in retailers that employ green practices, such as Chipotle Mexican Grill Inc., which Robinson calls the "restaurant version of Whole Foods" for its commitment to purchasing local and organic foods.
Other clean energy funds, such as mid-cap growth Calvert Global Alternative Energy Fund, have also bounced back after last year's declines. Winslow's fund is older than Calvert and invests in green concepts beyond just alternative energy.
The ride can be bumpy. The Green Growth Fund generates above-average volatility compared with other funds in its benchmark Russell 2000 Growth Index, Robinson said. "But in order to beat the index, I've learned, you don't want to look like it and you don't want to act like it," Robinson said.
In the long-term, the strategy has been "more right than wrong," he continued. As of May 31, the fund had returned an annualized 7.3 percent since it registered as a public fund in April 2001. The Russell 2000's annualized returns were down 1.1 percent for the same period.
But it can lead to periods of steep decline, such as the 61 percent drop in 2008.
"We believe that even though the stocks traded way down, like oil, that the fundamental business models were very much intact," he said. "In fact, most of these companies continue to grow in a negative growth environment."