Gadenin日本語Get the appThe stems root where they touch soil
The most useful thing to know about trailing verbena is that it layers itself. Where a trailing stem lies flat on damp soil, roots form at the leaf joints within two or three weeks in warm weather. You will often find this has already happened without any intervention: lift a stem that has been resting on the bed and it resists, because it has anchored itself in three or four places along its length.
That habit is free propagation. It also means the plant spreads sideways in open ground more than the original spacing suggests, so if you want it to stay in one place, lift the trailing stems off the soil occasionally rather than letting them anchor.
- Pick a healthy trailing stem in early or midsummer Choose one at least eight inches (20 cm) long with several leaf joints along it. Avoid any stem showing gray mildew dust, because you will simply propagate the problem.
- Press a leaf joint into contact with damp soil Bend the stem down so a leaf joint sits flat against the soil surface. Scrape a shallow depression first if the ground is uneven; the joint needs firm contact, not burial.
- Pin it down and cover lightly Hold it with a bent wire, a hairpin or a small stone. Cover the joint with half an inch (1 cm) of soil or compost. Leave the leaves and the growing tip exposed above the surface.
- Keep that spot damp and wait two to four weeks Water the pinned area when the surface dries. After two weeks tug the stem gently; resistance means roots have formed. In warm weather this is usually done within three weeks.
- Sever and lift the new plant Cut the stem between the new roots and the parent plant, leave the rooted piece in place for another week to settle, then lift it with a trowel and move it or pot it up.
Cuttings, taken while the growth is soft
Cuttings give you more plants than layering and let you carry a plant you like through the winter under cover. Take them from late spring through late summer, while the shoots are still soft and flexible. Woody stems from the base of an old plant root badly and are not worth using.
Take three to four inch (8 to 10 cm) tips in the morning while the plant is turgid. Cut just below a leaf joint, strip the lower leaves off so the bottom half of the cutting is bare, and pinch out any flower buds. Buds are the main reason cuttings fail: the plant will keep trying to flower rather than root, and it exhausts itself doing it. Push the cuttings into a gritty free draining compost around the edge of a pot, water once, and keep them somewhere bright but out of direct midday sun.
Cover the pot loosely to hold humidity but not tightly. Verbena rots easily in a sealed environment, so a propagator lid left slightly open or a clear bag held clear of the leaves is better than a bag sealed against the foliage. Rooting takes two to three weeks in warm conditions, and you will know it has worked when the tips start growing again.
| Factor | What to aim for | Why |
|---|---|---|
| Cutting length | 3 to 4 in (8 to 10 cm) | Enough stem to support itself without wilting |
| Where to cut | Just below a leaf joint | Roots form most readily at the joint |
| Flower buds | Remove every one | Flowering competes directly with rooting |
| Compost | Gritty and free draining | Wet compost rots verbena stems before they root |
| Temperature | 65 to 75F (18 to 24C) | Below 60F (15C) rooting slows to a crawl |
| Humidity | Covered loosely, ventilated daily | Sealed air causes rot and mildew on the cuttings |
| Time to root | 2 to 3 weeks | Longer than a month usually means it has failed |
Carrying plants through the winter
In climates where the plant is treated as an annual, cuttings taken in late summer are the way to keep a plant you liked. Root them before the nights turn cold, pot them individually into three inch (8 cm) pots once rooted, and keep them somewhere frost free and bright over winter, around 45 to 55F (7 to 13C).
Winter care is mostly restraint. Water only enough to stop the compost drying out completely, perhaps once every two weeks, and do not feed at all. Overwatered cuttings in a cold dim room rot at the base; that, not the cold itself, is what kills most overwintered verbena. In late winter, as the light returns, pinch the tips to make them branch and start watering a little more. They will be ready to harden off and plant out once the frosts have finished.
Take twice as many cuttings as you need. They are quick, the material is free from a plant you are cutting back anyway, and a proportion will always be lost over winter.
Seed is the slow route
Verbena can be raised from seed but it is markedly less reliable than cuttings. Germination is slow and uneven, often taking two to four weeks and rarely finishing all at once, and the seed needs darkness to germinate, so cover it lightly rather than surface sowing. Sow into a free draining mix, keep it at around 70F (21C), and keep the compost only just moist; wet seed-starting mix rots the seedlings before they emerge.
Because seed raised plants vary and take a long time to reach flowering size, most people growing trailing verbena for a display rely on cuttings and layers instead. Seed is worth it if you want a lot of plants cheaply and can start them very early under cover.
Whichever method you use, note the date you took the cuttings or pinned the layers, and the date they rooted. Rooting times shift a great deal with temperature, and after one season your own dates are far more useful than any general figure for planning the following year.