From our perspective as snapdragons (Antirrhinum majus), timing is everything. We are technically short-lived perennials, but most humans treat us as cool-season annuals because our true perennial nature is only expressed in the mildest climates. Our internal biological clock is governed by temperature. We thrive in the cool conditions of spring and fall, as our metabolic processes function optimally when soil temperatures are between 55°F and 65°F (13°C-18°C). Planting us when it is too warm shocks our systems, causing excessive wilting and stress that stunts our establishment. Conversely, planting us too late in fall does not give our root systems enough time to anchor and gather resources before the freezing dormancy of winter, which we can tolerate once properly established.
The ideal planting time is not a single date but a window dictated by the cessation or threat of frost. For most zones, there are two primary opportunities.
For a vibrant spring and early summer display, you should plant us outdoors 2 to 4 weeks before your last expected spring frost date. The cool soil and air are invigorating. This gives our roots a chance to grow robustly in the moist, cool earth without the immediate stress of summer heat. We can then channel our energy into producing strong foliage and those iconic flower spikes.
For a spectacular autumn show and a head start on spring blooms, planting us in fall, about 6 to 8 weeks before your first expected fall frost, is often even better. This allows us to establish a formidable root system in the still-warm soil. We then enter winter as well-rooted, dormant plants. As soon as the sun gains strength in late winter, we awaken with a burst of growth, often flowering much earlier than spring-planted snapdragons.
Our seeds themselves have specific requirements. We require light to germinate, so merely pressing us into the soil surface is sufficient. The ideal temperature for our germination is 65-70°F (18-21°C).
For Zones 3-5: The winters are harsh and long. You should start us indoors 8-10 weeks before the last spring frost. Transplant us outdoors well after the danger of a hard freeze has passed, when the soil is workable and daytime temperatures are consistently cool. A fall planting is risky and often unsuccessful unless heavily mulched for protection.
For Zones 6-7: This is a sweet spot. You can start us indoors for early spring transplanting 4-6 weeks before the last frost. More reliably, you can direct sow or transplant us in early fall for blooms that last until a hard freeze and then return vigorously in spring.
For Zones 8-9: Your winters are mild. We can be planted in late fall for winter and early spring color. We will often bloom throughout your cool season. The intense summer heat is our enemy, so we are best grown as a winter annual.
For Zones 10-11: Your challenge is a lack of consistent chilling. We require your coolest season. Plant us in late fall for bloom throughout winter and into early spring before the heat causes us to decline. We will not tolerate your hot, humid summers.
