Gadenin日本語Get the appThe season in outline
A snapdragon year has four clear phases, and the decisions that matter are all at the joins between them. Seed goes in eight to ten weeks before the last frost and is grown on cool and bright. The plant is pinched at four pairs of leaves and planted out early, while the weather is still cold, because it is a cool season plant and wants to be flowering before high summer. It flowers, stalls in the heat, and is cut back hard. Then it comes again in autumn on longer stems.
Getting the timing right is mostly a matter of being earlier than instinct suggests. Snapdragons planted out with the tender bedding, once all risk of frost has gone, spend their best weeks as young plants and then run straight into the heat that stops them flowering. Planted out three or four weeks before that, hardened off properly, they are in full spike before the temperature becomes a problem.
In regions with mild winters the whole schedule shifts. Sow in late summer, plant out in autumn, and the plants root through the cool months to flower in early spring on stems no spring sowing can match, finishing before the summer heat rather than being interrupted by it.
The table below sets out the year by stage rather than by month, so it reads the same in either hemisphere. Work backward from your own last frost date to place the sowing, and everything else follows from that.
| Stage | Timing | What to do |
|---|---|---|
| Sowing | 8 to 10 weeks before last frost | Surface sow, do not cover, 65 to 70F (18 to 21C), water from below |
| Growing on | From first true leaves | Transplant, then grow cool and bright at 50 to 60F (10 to 16C) |
| Pinching | At four pairs of true leaves | Take the tip out once; expect eight to twelve spikes instead of one |
| Hardening off | 10 to 14 days before planting | Build up outdoor exposure; young plants take a light frost |
| Planting out | 2 to 4 weeks before last frost | 8 to 12 inches (20 to 30 cm) apart for tall types; stake now |
| First flush | 14 to 18 weeks from sowing | Cut whole spikes out low before pods form; feed every 3 to 4 weeks |
| Heat stall | Once days exceed 85F (29C) | Cut back by half to two thirds, water deeply, one light feed |
| Second flush | 2 to 3 weeks after cutting back | Longer stems, stronger color, runs until hard frost |
| Cuttings | Late summer to early autumn | Take non flowering side shoots from the regrowth; root in 2 to 3 weeks |
| Seed collection | When pods are brown and rattling | Tip spikes into a paper bag; store dry, viable about 3 years |
| Overwintering | After the first hard frosts | In mild regions cut back and leave in place; elsewhere lift or resow |
Late winter and early spring: the part that decides the year
Everything about the eventual plant is settled before it goes in the ground. Sow eight to ten weeks before your last frost, germinate warm at 65 to 70F (18 to 21C) with the seed on the surface in the light, then move the tray somewhere cool and bright the moment the seedlings appear. That switch from warm to cool is the whole of the technique, and skipping it produces drawn seedlings that never make a decent spike.
Transplant at the first true leaves, about three to four weeks from sowing, lifting seedlings by a leaf rather than the stem. Left longer, the fine roots of a thickly sown tray knit together and cannot be separated without tearing. Grow the transplanted plants on at 50 to 60F (10 to 16C) with as much light as you can give them.
Pinch at four pairs of true leaves, whether the plant is still in its cell or newly planted out. This is the single highest value minute of the season: one pinch converts a plant with one spike into a plant with eight to twelve. Do it once and do not repeat.
Harden off over ten to fourteen days and plant out two to four weeks before the last frost, into ground with some compost in it but not heavily enriched. Firm the plants in, water them, and get supports in for tall types straight away while the roots are still shallow enough not to be damaged by a cane.
- Count back from your last frost date Sowing is eight to ten weeks before it, planting out two to four weeks before it. Those two figures place the whole season, and they are the only dates you need to work out.
- Switch the seedlings from warm to cool on emergence Warmth germinates the seed and then ruins the seedling. As soon as shoots appear, uncover the tray and move it to the coolest bright place available.
- Pinch once at four pairs of leaves Take out the top half inch (1 cm) above a leaf pair. Skip this only if you specifically want single long stems for cutting.
- Plant out earlier than the tender bedding Hardened snapdragons take a light frost. Going out while it is still cold is what gets them into full flower before summer heat shuts flowering down.
Summer: flower, stall, cut back, flower again
Through the first flush the routine is simple. Water deeply at the base twice a week in dry weather rather than lightly every day, feed a balanced liquid feed every three or four weeks, and cut spent spikes out low rather than picking dead flowers off the top. Cutting whole spikes before pods form is what keeps the plant producing, because seed set is the signal that stops it.
From midsummer, add a weekly check of the lower leaf undersides for the orange pustules of rust. Found early, affected leaves can be picked off and binned. Found late, the planting is finished, and the difference between the two is about three weeks of not looking.
When days settle above 85F (29C) the spikes shorten, color fades, and flowering stops. Do not feed harder and do not pull the plants out. Shear the planting to a third or half its height while the foliage is still green, water it thoroughly, mulch, and give one light feed. It will look untidy for two or three weeks and then break from the base.
The autumn flush that follows is usually the better one, with longer stems and stronger color, and it runs on until the first hard frost. This regrowth is also the best material for cuttings, so take the shoots you want in late summer while there is still enough mild weather ahead for them to root and establish.
Autumn, winter and setting up next year
Leave two or three spikes to run to seed at the end of the season if you want seed or self sown plants, and cut all the others out so the rest of the planting keeps flowering. Collect the pods when they are brown and rattling, tip them into a paper bag, dry the seed for a few days and store it cool and dark with the year written on the envelope.
In mild regions, cut the plants back after the first hard frosts and leave them in place. Snapdragons are short lived perennials and a plant that overwinters regrows from an established crown, flowers weeks earlier than any spring sowing, and makes a bigger and better branched plant in its second year. Clear rusted material away rather than leaving it around the crowns.
Where winters are harder, treat them as annuals but keep the good ones as rooted cuttings in a frost free frame. Those young plants go out in spring well ahead of anything sown from seed and stand up to the summer far better than a seedling planted at the same time.
Before you clear the bed, write down the dates that mattered: sowing, first flower, the heat stall, the cut back, and the start of the second flush, along with where the plants stood and where rust appeared first. Five dates and a sketch of the bed are the whole record, and they turn next season from a set of guesses into a plan.
Do not clear snapdragons out in midsummer because they look finished. A planting that has stalled in the heat still has its autumn flush in front of it, and the beds most often emptied in high summer are the ones that would have given the best flowers six weeks later.