Gadenin日本語Get the appPlant once the soil is genuinely warm
Verbena is tender and sulks in cold soil. Wait until all danger of frost has passed and the soil has reached about 60F (15C) at a depth of three inches (8 cm). Planted into cold wet ground it sits without rooting, which is the state in which crown rot most often takes it. A fortnight of patience costs nothing and a plant put out into warm soil catches up within days.
If plants have been raised under cover, harden them off for seven to ten days first. Put them outside in a sheltered spot for a few hours on the first day, extend the time daily, and leave them out overnight for the last two or three nights before planting. Skipping this step shows up as bleached or scorched foliage in the first week outdoors.
Choose the site for sun and for moving air
Two things matter when picking the spot: at least six hours of direct sun, and air that actually moves through the planting. The second is the one people get wrong. A bed against a fence in a sheltered corner may have perfect light and still produce mildewed verbena every year, because the foliage never dries and the humidity sits in the canopy.
Drainage is the third requirement. Verbena tolerates poor thin soil happily but not soil that stays wet. On heavy ground, work in coarse grit or plant on a slight ridge so water runs away from the crown. In containers, use a free draining compost with added grit or perlite and make sure the drainage holes are open. Do not enrich the soil heavily with compost or manure; verbena flowers best on lean ground, and rich soil buys you leaf rather than flower.
Spacing is the decision that matters most
Trailing verbena spreads far more than its nursery pot suggests, often 18 to 24 inches (45 to 60 cm) across in a season. Planted at the tight spacing that looks right on planting day, the plants meet in a month, the interior of the planting stops drying out, and mildew follows. Plant so that it looks slightly sparse for the first few weeks. It will fill in, and it will stay healthy while it does.
| Where | Spacing | Notes |
|---|---|---|
| Open bed or border | 12 to 18 in (30 to 45 cm) apart | Wider on a sheltered site where air does not move |
| Along a path or wall edge | 15 in (38 cm), one row | Keep at least 6 in (15 cm) clear of the wall itself |
| Trough or window box | 10 to 12 in (25 to 30 cm) apart | Two plants in a 24 in (60 cm) trough, not three |
| Hanging basket, 12 in (30 cm) across | Three plants around the rim | Leave the center for something upright or plant nothing |
| Mixed container with other bedding | Verbena at the edge only | It trails over the rim and keeps its own air on the outside |
Planting, step by step
The planting itself is quick, and the only two things to be careful about are depth and firming. Verbena resents being buried and resents being left loose in an air pocket in equal measure.
- Water the plants an hour before you start A moist rootball slides out of the pot intact and takes up water immediately afterwards. A dry rootball planted into moist soil can stay dry for a fortnight because water runs around it rather than into it.
- Dig a hole slightly wider than the rootball and the same depth Not deeper. The point where the stems meet the compost should end up level with the surrounding soil surface or a fraction above it, never below.
- Tease the outer roots loose If the roots are circling the pot, pull the outer ones free with your fingers so they grow outwards rather than continuing in a spiral. Do not shred the whole rootball apart.
- Backfill and firm gently Fill around the rootball and press with your fingertips, not your heel. You want no air gaps and no compaction. Leave the crown sitting proud rather than in a dish that collects water.
- Water in thoroughly once Give each plant a full can of water at the base to settle the soil around the roots. Then leave it; the next watering is decided by the soil, not the calendar.
The first three weeks, and what to record
For the first two to three weeks the rootball has not yet grown into the surrounding soil, so check it directly rather than checking the soil an inch away. Push a finger down against the side of the rootball; if that is dry while the bed around it is damp, water the plant itself. After three weeks the roots have spread and normal watering by feel takes over.
Pinch the growing tips out once, about two weeks after planting, taking half an inch (1 cm) off each leading shoot. This costs you nothing visible and doubles the number of stems, which is what makes the difference between a plant with a bare middle by midsummer and one that stays full. Do not feed at all during these three weeks; the plant is rooting, and feeding now pushes top growth it cannot yet support.
Write down the planting date, the spacing you actually used, and where each plant sat. Next year, when you know which plants stayed clean and which mildewed, that spacing note tells you exactly how much room your own site needs.
If a newly planted verbena wilts at midday but recovers by evening, it is short of root, not short of water. Resist the urge to water again; check the rootball and shade it for a couple of afternoons instead.