Zone: 3 to 8
Soil: sand to loam
Light: Full sun to part sun
Bloom colour:white, blue, violet, purple
Bloom period: June to August
Height: See notes
Moisture:Usually medium to dry
Attracts: A variety of bees and butterflies.
Notes: The native vervains can be a useful plant in a suburban garden and are moderately attractive to butterflies and bees, including the oligolectic species in Calliopsis. All Verbena species contain flowers on spikes and have petals that are somewhere in the blue spectrum of colours. The flowers bloom up the spikes. As the spikes continue to grow, new flowers can open up, which results in a bloom time of up to two months. The species mentioned here are found in most of the states or provinces east of the rockies.
Verbena simplex is the most garden worthy species and it can be used at the front of the border as it grows less than two feet high. The flowers are small, so it only looks good when at least 5 specimens are planted together about 12 inches apart. It is in flower from early to mid-summer. This species is adapted to a dry and well-drained soil. It is pollinated by hover flies and the odd bee.
Verbena stricta grows to about 4 feet high and thrives in dry soil. It will reproduce easily by reseeding. The leaves are coarser than V. simplex, but they have a soft feel to them. Compared to V. simplex, the flower spikes are much larger and more noticeable. The plant will do well with a trellis support to keep the plant upright in storms. It flowers for about six weeks in the middle of summer. There is a lot of foliage and it should really be planted behind smaller plants.
Verbena hastata is a species that typically grows in wet meadows up to 5 ft high, but it can also be found in disturbed areas in parks as long as some moisture is there. It has the nicest flowerheads, which are purple, but the leaves are coarse resulting in an overall weedy appearance. Out of the three species mentioned, V. hastata has the greatest attraction to wildlife with bumblebees being regular visitors. Although the foliage is not that appealing, this species has been grown in botanical gardens with great effect and it will grow well in regular garden soil.
If you are contemplating keeping It in your garden, then it should be planted behind other plants to conceal most of the foliage. It grows around 5 feet high. It is worth bearing in mind that it spreads by rhizomes and has a fibrous root system so it will not work well in a small suburban garden. In any case, I would not plant a single specimen. As a part of a minimum grouping of three, this plant can look wonderful in a garden and a pink cultivar is sometimes available. You could try cutting it back when it is 3 ft high by 15 inches to reduce the amount of foliage.