In New York, the creep of spring has been, as it always is, taunting and completely unreliable. But the bursting cherry blossoms and magnolias triggered my interest in the best outdoor planters on the market—ones that are beautifully glazed, Florentine, sturdy, classic—but nothing so strictly terra-cotta you could snag it at the grocery checkout. Bergs Potter takes the cake for me, closely followed by the majolica-like planters at Williams-Sonoma and a few stylish designs from Ferm Living and Pottery Barn. These planters lean home decor over plastic planters, making them weather-resistant, durable pieces even on a wind-whipped balcony or hurricane-sacked home garden. My yardstick is quite simply: Can it yield a happy basil plant?…