Last updated on May 17th, 2022
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Verbena bonariensis is a beloved prairie style plant that brings to any garden butterflies and bees alike. It produces sturdy upright stems that will tower gracefully above the rest of your garden giving you all the vertical designs you need when adding different layers of height. In fact, they can grow up to two metres once they are fully established and during that time they produce clusters of bright purple flowers throughout the entire summer. They truly are a spectacular perennial plant.
How to grow Verbena bonariensis
These plants prefer moist but well-drained soil and grow well in a sunny position. If they are given the right conditions they will reward you with a fantastic display of purple flowers, but given the wrong conditions, you will miss out on what makes these plants so special.
Deadhead them regularly to prolong flowering and prevent them from going to seed
They, of course, should be cut back every autumn once they have finished flowering to give them a little tidy up, but apart from that, they don’t require much more. When grown in the right conditions they will self-seed unless you stop them by removing spent flowers to stop them from doing so. This is usually a good idea because it also encourages the flowering to be more prolific.
Plant in fertile well-drained soil in a sunny location and dig in plenty of organic matter
In addition to making sure they have everything they need, they like to be planted in an area that has moderately fertile soil with proper drainage. There is a lot you can do to amend the drainage if you happen to have very compact soil. We recommend digging in plenty of organic matter or multi-purpose compost when planting to give them the best start.
How to plant Verbena bonariensis
If you grow them from seed you can sow the seeds directly into the ground in the spring. If you don’t want to do this you can start them off at the end of winter inside, the same way you would propagate seedlings from other plants under glass and then place them outside in the spring, after all the danger of frost has passed in your area, which for most of the UK is around May.
Learn how to sow perennial seeds in this guide
Caring for Verbena bonariensis
In spite of how tall they grow to, Verbena bonariensis do not need staking. The stems are quite large and thick so they will hold themselves up just fine. In fact, if you are trying to grow neighbouring perennials, you can even use the stems from these plants to provide support for smaller, weaker plants.
Deadheading and pruning
They do not require deadheading and they will self-seed if you let them. You might want to remove the spent flowers for aesthetic purposes and it also encourages them to flower for longer.
In terms of pruning, you want to prune it back to the ground after it has finished flowering to protect it during the winter. If you live in the Northern regions of the UK you might want to add mulch, for example, a few inches of compost of leaf mould in the autumn and straw around the base to protect the roots.
Learn how to make leaf mould in this guide we have written
Learn how to make home made compost in this guide
Propagating Verbena bonariensis
Sowing seeds
As previously mentioned, they will self-seed if the conditions are right so if you want to grow multiple Verbena bonariensis in your garden you really need do nothing other than successfully grow the one and allow it to self-seed and propagate.
However, you can also collect the seeds before they propagate on their own and sow them directly into the garden somewhere else in order to add more elsewhere.
Sowing indoors
You can also sow them indoors in a seed tray, using seed compost or multi-purpose compost and cover with a thin layer of vermiculite. Place them into a propagator or cover the tray with clear plastic. The seeds need to be at a temperature of between 24°C and 27°C in order to germinate. This germination may take two to three weeks.
Once they have germinated, prick the seedlings out into small 7cm or 9cm pots and grow them on until they are well-rooted. Harden off and then plant out into their final positions when the risk of first has passed, usually around mid May.
Taking cuttings
If collecting seeds isn’t something you want to do you can propagate Verbena by taking cuttings at the beginning of autumn and growing these cuttings in small pots. Take cuttings from the side shoots and not the main stems, the side shoots usually just pull off the main stem but you can also cut them off. You’re looking for good-sized cuttings around 20cm long.
Remove the lower leaves and pot them on into good quality potting compost. They usually start to root within a few weeks. Plant them into their final positions in spring.
Pests and Problems
Verbena bonariensis doesn’t really have a lot of pests that you will need to worry about. The biggest issue you might experience is protecting them over winter, although this just means cutting them back and covering them with mulch to protect the roots. Other than that these grow very well and very easily with very few diseases or pests.
They are, however, sometimes effected by powdery mildew, and as soon as you notice this we recommend spraying with a fungicide and removing any badly affected leaves.
