Push the limits of your garden’s USDA zone by finding a microclimate where plants that like it a bit warmer may flourish. A, C Stachyuris ‘Magpie’ fruit and variegated leaves; B the color-changing flowers of Nicotiana mutabilis; D Lagerstroemia ‘Cherry Dazzle’; E Geranium ‘Jolly Bee’; F Hesperola parviflora.

 

In the early 1930s, the Women’s Auxiliary of the New York Botanical Garden engaged the landscape architect Ellen Biddle Shipman to design a long, mixed border of trees, shrubs, and perennials running the 260-foot length of the southeast side of the garden’s conservatory. Known as The Ladies’ Border, the plantings were redesigned in 2002 by Lynden B. Miller, the city’s leading designer of public installations who has created works for Bryant and Battery parks among others. Today, this border functions as an experimental hardiness test garden featuring species and varieties that are questionably suitable for winter in the Bronx, New York.

Protected by the conservatory to the north and in full sun for most of the day, a surprising number of heat-loving plants thrive in this area where they have not been expected to survive. Camellias bloom in winter. Rosemary plants flourish and are nearly always evergreen. Eucomis varieties, called pineapple lilies, are bulbs that winter over and bloom every year, and the crape myrtles familiar to southern gardens bloom in amazing variety.

This area could be considered a microclimate, and you may have a few places in your garden where you too could try and cheat the USDA hardiness zone recommendations. A south-facing spot (ideally up against the foundation of the house) might be a place to plant half-hardy bulbs. Even planting next to a large boulder might add half a zone. A corner with a windbreak of shrubs could be a spot for a broadleaf evergreen Mahonia with leaves and flower buds that are often wind-burned in winter. A useful niche might be on high ground where cold air drains away.

Bodies of water, even as small as a pond, can alter the air temperature. Lakes and oceans have their own mitigating influences. A lake helps mitigate rapid changes in air temperature. The oceans take much longer to cool down in winter and to warm up in spring. The ocean provides more viewing time in fall before a frost puts an end to that season and, later, protects precocious bloomers by keeping the air cool so their buds do not emerge too early and get damaged by frost.

We gardeners often dare to grow things that conventional wisdom warns us not to. Tony Avent, the co-owner of Plant Delights Nursery in North Carolina, often challenges both wisdom and climates. His motto: “I consider every plant hardy until I have killed it myself... at least three times.”

The Ladies’ Border at the New York Botanical Garden challenges the climate zones.