Monday, March 1, 2010

Bidens in the Garden --- Beggarticks, weeds or not?

The name Beggarticks may not give you a warm, happy feel for a plant to add to your garden. Many of the plants in this genus do not have strong aesthetic qualities that appeal to the general public, BUT a few of these do and are worth considering.  This is another chapter in my experience of working with native annuals and biennials.

Most Bidens species share the trait of having seeds that stick to anything passing their way. In Latin, bidens refers to having two teeth, in this case the two teeth on the seed. The flowers of many Bidens species have diminutive yellow to white ray flowers, rendering the bloom insignificant for the human observer, but still just as valuable to insects (its the disk flowers that matter). Also these plants produce a lot of seed that can be long lived in the soil. With these caveats in mind let me mention several species that have greater visual appeal and can work well in a garden setting.

The first is Swamp Marigold, Bidens aristosa var. mutica. This plant is the exceptional in that it has the largest ray flowers of the genus. Also, while the seed possesses the two teeth typical of the Bidens, these are not able to catch hold like the others. B. aristosa’s range extends from the Maine to Georgia and as far west as Oklahoma.

As the common name implies, Swamp Marigold’s native habitat is wetlands, growing in full sun, or part sun on a woodland edge. Its growth habit is upright with many branches, forming a rounded shrub-like plant 3-5’ in height. It produces a large number of sweet scented yellow flowers, measuring to 2” in diameter. Blooming begins August with a burst of color and continues to October at a slower rate. Flowers are very attractive to bees. I have found that deadheading was effective at improving the second flush of blooms. Also the blooming period was independent of the location of the plant. Plants in pots, different soils, sun and moisture conditions all started to bloom within 2 weeks of each other. If you want a smaller plant, it can be cut back in late June without compromising the floral display.

Unlike many other tap rooted plants, this plant tolerated transplanting well. While somewhat stunted in size, plants transplanted from small pots into the ground as late as July, still put on a good show. I also noted that wherever the stem touched the soil, new roots would be produced. So while the best habitat for the plant is in wet soils, I found it to be adaptable to drier soils, even to the point of surviving as a container plants that were repeatedly dried to the point of wilting!

Seed for Bidens aristosa var. mutica is available from several sources including Prairie Moon Nursery. In my test moist stratified seed (90 days/40F) showed a very high rate of germination. In fact, germination had started while still under refrigeration in the dark. One potential difficulty in a native annuals garden is that the seedlings look the same as those for 'weedy' B. frondosa, Devil’s beggarticks. Differences will become apparent as the mature leaves appear, the leaflets of B. aristosa are much more deeply toothed.  In my garden I have Sulfur Cosmos (Cosmos sulfureus) growing from seed in the same bed. The plants look very similar, but the first set of true leaves of the Cosmos are rounded, not pointed. Also the Cosmos comes up several weeks after the Bidens seedlings first appear.

There are three other annual Bidens native to the Northeast US worth mentioning here. All of these grow 3-4 feet tall and prefer moist to wet soils.
  • Smooth Bidens, B. laevis, has flowers that are slightly smaller and nod downward when in full bloom. Seeds are available from Native Ventures in Louisiana.
  • Nodding Beggarticks, B. cernua, also has smaller flowers, but the bloom starts as early as June, extending to Septmeber.  
  • Northern Tickseed Sunflower, B coronata.  For the taxonomists out there there corrected name for this plant is B. trichosperma, but it will take some time for this to be updated.  Seeds for these last two plants are available from Prairie Moon Nursery.
All three of these species are indigenous to the eastern half of Massachusetts.

I will be trying out the Northern Tickseed this year and comparing it to the Swamp Marigold. One thing I will watch for is how popular the flowers are with pollinators. Northern tickseed is a Massachusetts native, while the swamp marigold, while found in the wild, is not listed as indigenous to Massachusetts.

Bidens ferulifolia – Apache Beggarticks

The last member of the genus I will mention here is Apache Beggarticks. These are low growing perennials originally found growing in open fields in southern Arizona and into Mexico. As the species, this plant has small yellow flowers; however, a number of larger flowered cultivars have been developed that perform well as annuals in gardens here in the Northeast. The species name ferulifolia is a reference to the fennel-like foliage.

Several cultivars of this plant are available as seeds and as small plants from nurseries. An example is B. ferulifolia ‘Peter’s Golden Carpet’ available from Proven Winners. This cultivar grows 10-15” in height and spread, producing copious amounts of honey-yellow, 5-7-petaled flowers, 1-1.5” in diameter, from mid-summer to frost (earlier if starting from nursery stock). This Bidens likes full sun and average soil moisture (mesic), thought it will tolerate droughty conditions. These plants perform well on the front edges of a border and in hanging baskets. Plants that I have observed returning from seed in Cambridge, MA have retained the character of the cultivar over least 3 years.


Curbstone Valley Farm said...

They're too beautiful to be weeds. We have a species here, Bidens laevis, also known as Joaquin Sunflower. Even though we have two creeks on the property I haven't yet seen any natively growing here, but have considered planting them.

joene said...

Very imformative, Adam. Sorry it took me a month to read this. Thanks.