All types of verbena are technically perennials although in many parts of the United States, they are grown specifically as a warm-season annual. Propagating Verbena is done by softwood stem cuttings or seeds no matter if you grow your Verbena as an annual or perennial. Growing from seed starts typically in the late winter so that the plants are large enough to plant out in the late spring or early summer. Softwood cuttings are best taken early in the summer to provide flowering plants late into the fall or late summer to allow for overwintering the plants as houseplants.
Methods To Propagate Verbena
All varieties of Verbena are easily propagated by either softwood cuttings or seed starting. The tall types (and most types native to North America) which are fully winter hardy from USDA zones 6-11 frequently self-seed, in which case the seedlings that appear the following spring are easily dug up and transplanted to other spots in the garden.
The more tender Verbena that is grown mainly as an annual container plant can be propagated by softwood cuttings through the growing season to fill containers and empty spots in the garden. The cuttings are relatively quick to strike and ready to plant on in a few weeks.
What You Need To Propagate Verbena
For cuttings: Softwood cuttings need to have consistent moisture and high levels of humidity to encourage healthy root growth. The easiest way to achieve this is to use a potting medium that is both well-draining and able to retain moisture for long periods. Straight perlite is ideal. It is chunky enough to allow air circulation, good drainage and also sucks up moisture in its micropores to slowly release it as the plant requires.
The next best potting mix would be a lightweight blend of all-purpose potting mix with an equal portion of perlite added.
Small plastic pots between 3-4 inches in diameter can hold 5 cuttings of Verbena comfortably. A plastic baggie is used to make a small greenhouse dome over the pot. Attach it to the pot with a rubber band or twine so that it is well above the top leaves and does not touch any part of the cuttings. Rooting hormone powder is not necessary for softwood cuttings as they typically strike easier and at a faster rate than more mature hardwood cuttings.
For seeds: Starting seeds Verbena seeds is always done in the late winter indoors where the temperature and light levels can be controlled. A grow light and heat mat are ideal pieces of equipment, although not completely necessary. If you have a window with direct sun exposure (South or Southwest facing) in a warm room that consistently remains at 68F or above that is sufficient to start Verbena from seed.
Small plastic pots, either 3-4 inches in diameter, and a good draining and finely textured seed starting mix are the other materials needed for healthy plant starts. Ensure that pots are clean and free of old potting mix which can harbor disease spores like Damping off which is deadly for new seedlings.
Fresh seed starting mix should also be used to reduce any chance of disease infection. A watering can or plastic bottle fitted with a bottle top watering attachment is great for gently watering seedlings after germination without dislodging them from the seeding medium.
Best Time To Propagate Verbena
For cuttings: Take cuttings early in the summer from the annual Verbena to grow through the season. Perennial Verbena also supplies good material for cuttings early in the summer before they begin to for flower stems. Only take side shoots of non-flowering stems for the most vigorous plant starts.
Cuttings can be taken to overwinter plants in colder gardening zones. Take these cuttings well before fall and make sure to grow them in a warm location with bright direct sun exposure.
For seeds: Start Verbena seeds 8-12 weeks before you want to plant them outdoors. VErbena is a tender perennial and will not tolerate cold nighttime temperatures below 45F. The best time to plant out Verbena as an annual is in mid to late May when the other warm season plants such as tomatoes and peppers are planted.
Collect seeds from Verbena late in the summer after the seed pods have fully dried but before they open up and release seed. The seed needs to be stored in a breathable container like a paper envelope and placed in a cool, dark location until needed. The seed will remain viable for 2-3 years.
Steps To Propagate Verbena
The quickest way to have many Verbena plants is to start them from seed late in the winter. No matter if they are grown as an annual or perennial they will need at least 8-12 weeks of indoor growing before being ready to plant outdoors.
Step 1 - Fill a plastic pot or shallow seed tray with pre-moistened seed starting mix and press firmly to give the seed a good base to root into.
Step 2 - Scatter the seeds thinly and evenly over the surface of the potting mix.
Step 3 - cover the seed with a thin layer of seed starting mix to exclude light. Verbena does not need light to germinate.
Step 4 - Cover the pot or tray with a plastic bag or mini greenhouse dome to maintain high humidity around the seeds. Then place this on top of a heat mat or in a warm spot like the top of a refrigerator until the seeds just start to germinate. Typically this takes up to 3 weeks for many types of Verbena.
Step 5 - Keep the pot or seed starting flat moist by watering the container from the bottom or lightly misting the seed starting mix with filtered water as needed.
Step 6 - Once germination has started and green shoots are visible remove the greenhouse dome (or plastic bag) and place the seedlings under a grow light no further than 4 inches above the pot. Keep moving the light as the seedlings grow. This helps to keep the seedlings sturdy and straight.
Caring For Young Verbena Seedlings
Let the seedlings grow until the first set of true leaves appears. These leaves will be quite different from the initial cotyledon leaves, which are rounded and yellow as the seedling matures. Continue to water the seedlings enough that the potting mix stays slightly damp and does not dry out fully. Overwatered seedlings are the most common reason that plants fail. Also, make sure that there is plenty of air circulation around pots. Transplant seedlings into individual 3-inch pots filled with a mix of 1 part all-purpose potting mix and 1 part seed starting mix.
Carefully do this by teasing the plants out of the starting pot or tray without damaging either the roots or the stem. Only hold the seedling by the leaves as they are easily re-grown if damaged. Continue to water the seedlings sparingly and keep them under grow lights set on a timer for 12-16 hours of light a day. Feed the pots once every 2 weeks with a very dilute liquid fertilizer.
A few weeks before planting outside, pinch out up to one inch of top growth just above a set of leaves to encourage branching and a bushy form for the plant.
Allow for at least one week of hardening off and transition time when the outside temperatures are reliably above 50F at night. Move the new plants to a shaded location for a couple of days, then gradually move them to a location in full sun over the course of a week. Placing the new plants directly in a full-sunw location will result in burned or scorched leaves.
Sources:
“New Plants from Cuttings”, Indiana Yard and Garden- Purdue Consumer Horticulture. www.purdue.edu
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Author Robbin Small - Published 12-27-2024 |