Gadenin日本語Get the appThe shape of the season
Verbena is straightforward across a season provided you do a small number of things at the right moments. The table below is the whole year in outline; the sections after it explain the reasoning behind each stage.
| Stage | Main job | The decision point |
|---|---|---|
| Late winter | Sow seed under cover if raising your own | Only worth it if you can hold 70F (21C) and good light |
| Early spring | Pot up and pinch young plants | Pinch once the plant has four or five pairs of leaves |
| Mid spring | Harden off over seven to ten days | Do not rush this; scorched foliage sets the plant back weeks |
| Late spring | Plant out into warm soil | Soil above 60F (15C) and frosts finished |
| Early summer | Pinch two weeks after planting, first flush opens | Do not feed until the plant is clearly rooted and growing |
| Midsummer | Cut back by a third when the middle goes bare | Do it while there is still time to rebuild before autumn |
| Late summer | Take cuttings, keep shearing after each flush | Take cuttings before nights drop below 55F (13C) |
| Autumn | Best flush of the year in many climates, then wind down | Stop feeding entirely once nights cool |
| Winter | Keep cuttings frost free, barely watered | Water only to stop the compost drying out |
Spring: raising, hardening and getting into the ground
Young plants raised under cover need pinching once, when they have four or five pairs of leaves, to make them branch from low down. A plant that goes out as a single unpinched stem will always be leggier than one pinched early, and no amount of later shearing entirely makes up for it.
Hardening off takes seven to ten days and cannot be shortcut. Start with a few sheltered hours outside and build up to a full night out. Then plant into soil that has genuinely warmed, at least 60F (15C), and space the plants wider than looks right, 12 to 18 inches (30 to 45 cm) apart in a bed. That spacing decision is the single largest influence on whether you spend the summer dealing with mildew.
Early summer: rooting in, the first flush, and no feeding
For the first three weeks after planting the job is to get the plant rooted. Check the rootball itself rather than the surrounding soil, water when it is dry, and do not feed. Then pinch the leading shoots once more, about two weeks in, to double the number of stems.
The first flush of flowers arrives four to six weeks after planting. When two thirds of the heads have browned, shear an inch or two (2.5 to 5 cm) off the whole plant. If you are going to feed at all, this is the time to start, at half the strength on the label and no more often than every two to three weeks. A verbena kept lean flowers far harder than one fed generously, and rich feeding at this stage is what produces a lush plant with almost no flowers by high summer.
Midsummer: the cut back that saves the second half of the season
Partway through summer nearly every trailing verbena reaches the same state: the center of the plant is bare and stemmy, the leaves have thinned in the middle, and all the flowering has moved to the last few inches of each trailing stem. This is normal and it is the point at which light shearing stops working.
Cut the whole plant back by about a third, staying in the leafy part of the stems rather than cutting into bare wood. Water once afterwards and do not feed. There will be two to three weeks with little to look at while new shoots break from the leaf joints, and then the plant carries a full flush into autumn from a filled in, compact base. Done in the first half of summer this reliably buys the second half of the season. Left until the weather has already turned, the plant will not have time to rebuild.
This is also the moment to deal with any mildew that has appeared. Take out whole stems from the base to open the interior rather than just shortening everything, bin the affected foliage, and if the plant is in a container, move it somewhere with more air moving through.
Cut back a group of plants a week or two apart rather than all on the same day. You keep something in flower throughout, and you learn which timing works best on your own site.
Late summer and autumn: cuttings, then winding down
Take cuttings while the shoots are still soft and before the nights drop below about 55F (13C). Three to four inch (8 to 10 cm) tips, all flower buds removed, into gritty potting mix. They root in two to three weeks and give you plants for next year from material you were cutting off anyway.
Autumn is often the best flowering of the whole year, as the heat that suppressed bud production through midsummer eases off. Keep shearing after each flush and keep watering, but stop feeding entirely once the nights cool; late soft growth will not harden and simply gives frost something to blacken. When the first hard frost arrives, clear the top growth and bin any mildewed material rather than composting it.
Winter, and the notes that make next year easier
Overwintered cuttings need frost free conditions around 45 to 55F (7 to 13C), good light, water perhaps every two weeks, and no feed. Rot from overwatering in a cold dim room kills far more overwintered verbena than cold does. In late winter, pinch the tips to make them branch and increase the watering slightly as the light returns.
Over the winter, look back at what you recorded. The dates worth having are the planting date, the date of the first flower, the date of each shearing and the flush that followed it, the date you first saw mildew and on which plant, and the date you took cuttings and when they rooted. Note the spacing you used and where each plant stood.
Those notes turn the following season from guesswork into a plan. You will know how many weeks after shearing your own plants come back into flower, which corner of your garden holds still air and produces mildew every year, and whether your soil is rich enough that you should not be feeding at all.