Given the Mac’s tiny share of the worldwide PC market — roughly 3.5% as of June — Apple (AAPL) has a lot of room to grow. And grow it did in the second quarter, as a note to clients issued Monday by Needham’s Charlie Wolf makes clear.

Using IDC’s numbers for calendar Q2, Wolf takes a close look at Mac shipments in various market segments, from the home to the largest enterprises. Among his findings:

• At 35%, Mac shipment growth in June easily exceeded the market’s growth rate of 20.9%.
• Mac shipments grew 31.4% in the home market, topping the market’s growth rate of 25.2%.
• At 49.8%, the Mac’s growth in business was three times higher than the market’s 15.7%.
• Mac shipments in government grew 200%, sixteen times faster than the market’s 12.1%.

Breaking down the business portion of that data, Wolf found that Apple’s fastest growth was in the largest enterprises, as the chart below demonstrates.

Finally, Wolf singles out the “intriguing phenomenon” of the Mac’s continued surge in the European home market, where Apple’s unit share more than doubled since the first quarter of 2006 (from 3.4% to 7%) and its dollar share more than tripled (from 4.6% to 15.4%). See chart below.

“The key driver,” of Mac sales in the European market, Wolf writes, “appears to be the iPhone. The iPhone holds a higher share in the European smartphone market than it does in the U.S. because it is distributed through multiple carriers in most countries in this region. In addition, the halo effect emanating from the iPhone is undoubtedly stronger than the iPod halo effect.”

[Follow Philip Elmer-DeWitt on Twitter @philiped]