Snapdragon

Snapdragons are a Mediterranean flower pretending to be a spring annual, and their entire growing strategy depends on cool weather that most gardeners don't give them enough of. They want to bloom in April and May, rest through the heat, and bloom again in September if the nights cool down — which means they need to be started indoors ten weeks before your last frost, not six. A snapdragon sown in March and transplanted in May will bloom once in June and then sulk through July, often dying before the fall flush.

The seeds are tiny and slow to germinate — seven to fourteen days at 65 degrees, sometimes longer. They need light to sprout, so press them onto the surface of damp seed-starting mix and leave them uncovered. A humidity dome helps in the first week, but remove it as soon as you see green; snapdragons are prone to damping off if the air stays too humid. Once the seedlings have two true leaves, transplant them into individual cells and give them as much light as you can.

Transplant out while the nights are still cold. Snapdragons tolerate light frost — down to about 28 degrees — and they need that cold period to set strong roots and stocky growth. A plant hardened off and transplanted four weeks before the last frost will be fuller and produce more stems than one babied indoors until May. The trick is to not wait for warm weather; snapdragons perform best when you push them into cool soil.

Pinch the first flush of bloom. When the central stem produces its first flower spike, cut it off just above a set of leaves. The plant will respond by sending up multiple side shoots, each with its own flower spike, and the total yield over the season will be two or three times what you'd get from letting that first stem bloom out. This is the move that separates a snapdragon grown for one vase from a snapdragon grown as a cut-flower crop.

In summer heat — anything above 85 degrees for more than a few days — snapdragons tend to stop blooming and go semi-dormant. The leaves may yellow, the stems may stretch, and the plant looks like it's dying. It usually isn't. Cut it back by half, keep it watered, and wait. When the nights cool in late August or early September, new growth will often appear from the base, and the plant will bloom again. This second flush can be as productive as the first, and the flowers tend to have better color in the cooler air.

Rust is the main disease problem — orange pustules on the undersides of leaves that spread quickly in humid conditions. Once you see it, remove affected leaves immediately and thin the planting for better airflow. Rust-resistant varieties exist, but no snapdragon is immune if conditions favor the fungus.