Snapdragons (Antirrhinum majus) are a classic garden favorite, prized for their vibrant, spiky blooms and long flowering season. Starting these flowers from their extremely small, dust-like seeds presents a unique challenge. Starting seeds indoors offers the best chance for success, requiring a precise approach to meet their specific germination needs. This guide provides practical instructions for successfully starting snapdragons from seed indoors.
Preparing the Seed Starting Environment
To start snapdragons successfully, select a clean seed-starting tray, such as a 4-pack or 6-pack cell tray, ensuring it has adequate drainage holes. The small volume of these cells is ideal for managing individual seedlings without wasting seed.
The growing medium should be a sterile, soilless seed-starting mix, which provides a fine texture and reduces the risk of fungal diseases. Before sowing, thoroughly pre-moisten the mix until it is uniformly damp, but not saturated. This crucial step ensures that the tiny seeds have immediate access to moisture once placed on the surface.
Snapdragon seeds require light to germinate, making the proper lighting setup necessary. Placing the trays under supplemental grow lights is recommended, providing 12 to 16 hours of light daily. A bright south-facing window often lacks sufficient intensity, leading to weak, “leggy” seedlings.
Temperature control is also important, as snapdragons prefer cooler conditions for sprouting. The optimal temperature range for germination is between 65 and 75°F (18–24°C). Temperatures much higher than this range can inhibit germination, so a heat mat is generally unnecessary and sometimes counterproductive.
Determining the Ideal Sowing Density
The question of how many snapdragon seeds to plant per cell is answered by balancing the tiny seed size with the plant’s variable germination rate. The recommended density is to sow two to three seeds per cell. This practice ensures that at least one viable seedling will emerge without creating excessive overcrowding.
The rationale for planting a few extra seeds is simple: the minuscule nature of the seed makes it difficult to gauge viability, and a slightly higher density acts as a buffer against poor germination. Snapdragon seeds must be surface-sown, unlike larger seeds planted beneath the soil. They require exposure to light to trigger germination, a phenomenon known as positive photoblastism.
To manage the tiny seeds, specialized techniques ensure accurate placement. One common method uses a damp toothpick to pick up individual seeds and gently transfer them to the center of each cell. Alternatively, placing a small pinch of seeds on a folded piece of paper and lightly tapping it over the cells allows for controlled distribution.
After placing the seeds on the pre-moistened soil surface, press them down gently to ensure good seed-to-soil contact. Do not cover the seeds with the growing medium, as this blocks the necessary light. A very thin dusting of fine vermiculite can be applied to the surface; this helps maintain moisture around the seeds without blocking the light.
Managing Seedlings After Germination
Once the first tiny sprouts emerge, typically taking 7 to 14 days, the focus shifts to managing their growth. Maintain consistent, gentle moisture, but remove the humidity dome immediately. This increases air circulation and prevents damping off, a common fungal disease in humid conditions.
The most important post-germination step is thinning, which must occur once the seedlings develop their first set of true leaves. True leaves appear after the initial pair of seed leaves, called cotyledons, and resemble the mature snapdragon foliage. Thinning is necessary to prevent competition for light, water, and nutrients, which can lead to weak, elongated plants.
To thin, select the strongest, most centrally located seedling in the cell and remove the others. It is strongly advised to snip the unwanted seedlings at the soil line using small, sharp scissors or micro-tip snips rather than pulling them out. Pulling risks disturbing the delicate root system of the remaining, desired seedling, potentially causing significant damage.
Before transplanting the single, robust seedling into the garden, it must undergo a process called hardening off. This involves gradually acclimating the young plant to outdoor conditions, including direct sunlight, wind, and cooler temperatures, over a period of seven to ten days. This slow transition prevents transplant shock and ensures a strong start in the garden.