When to Plant What: A Pennsylvania Homeowner's Seasonal Guide

If there is one question we answer more than any other, it is this: when should I plant? Pennsylvania's climate is specific enough that generic gardening advice — written for national audiences — regularly leads homeowners astray. This guide is written specifically for properties in King of Prussia, Montgomery County, and the Greater Philadelphia area.

Understanding Pennsylvania's Hardiness Zone

The Greater Philadelphia region sits in USDA Hardiness Zone 6b to 7a. What this means practically: our last spring frost falls somewhere between April 1 and April 15, and our first fall frost arrives between October 15 and November 1. Every planting decision should be oriented around these two dates.

Zone 6b also means our winters are cold enough to kill plants that would thrive further south, and our summers are humid enough to create fungal pressure that drier climates never see. Variety selection matters as much as timing.

Spring Planting: March Through May

Spring is when most homeowners feel the urge to plant — and it is a good season for most things, with important caveats.

• Late March to early April: Cool-season annuals (pansies, snapdragons) and vegetables can go in once soil temperatures reach 45°F. These tolerate light frost.
• Mid to late April: Most perennials, ornamental shrubs, and warm-season annuals. Wait until after the last frost date before planting anything frost-sensitive.
• May: Ideal for trees and large shrubs. The plant can establish its root system before summer heat stress arrives. Early May is the sweet spot.

One critical note: spring-blooming bulbs (tulips, daffodils, crocuses, hyacinths) are not planted in spring. They require cold stratification and must be planted in fall. Many homeowners are disappointed to learn this after the tulip season has passed.

Summer Planting: June Through August

Summer is not an ideal planting window for most trees and shrubs. Heat stress combined with establishment stress can kill otherwise healthy plants. If summer planting is unavoidable, choose heat-tolerant species, plant in the evening, water deeply at planting, and commit to consistent irrigation through August.

Ground covers and ornamental grasses handle summer planting better than most. Container-grown plants also establish more reliably than balled-and-burlapped specimens when planted in summer heat.

Fall Planting: September Through November

Fall is actually the best planting season for most Pennsylvania landscapes — and many homeowners do not realise it. The logic: soil stays warm well into October (roots keep growing even as tops go dormant), air temperatures are cooler (less stress on the plant), and winter rain and snow provide moisture without irrigation.

• September and October: Prime time for trees, shrubs, and perennials. This is especially true for anything you want established before next summer.
• September specifically: The single best month for overseeding or establishing a new lawn in Pennsylvania. Soil temperature is ideal and competition from weed seeds is lower.
• October through early November: Spring-blooming bulbs. Get them in the ground before a hard freeze locks the soil — typically by mid-November in Montgomery County.

The Mistake We See Most Often

Panic-planting in June because a garden looks bare. By July, those plants are fighting heat stress and the homeowner has committed to a watering schedule that lasts all summer. The same plants installed in October would have established quietly over winter and been thriving by June without any intervention.

Patience and timing consistently outperform effort and expense in landscaping.