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Landscape Design Native Plants

question on biennial flowers (such as Black-Eyed Susan)

last year

I'm trying to see if I understand how biennial flowers works. If a flower is biennial, does that mean it will not flower until its second year? And, once the plant flowers, those particular flowers/plants will die after one year and not return. However, the dried seedheads will release new seeds, so that the cycle always continues...the plant is constantly self-sowing. So while the individual plants/flowers are considered Annuals,, they take two-years to each develop, and even though they die after that, in some ways it's Perennial only because it self-sows so readily..

Do I sorta have that right? Or may I indeed need to toss a few additional BES seeds onto the site, every year, to ensure a continual good-sized patch of BES flowers in my garden?

Thanks!

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Comments (4)

floral_uk z.8/9 SW UK
last year
last modified: last year
Correct up until the end of the third sentence. Then it gets confused.

Annuals are plants which grow from seed, flower, produce seed and die within a single growing season. So biennial flowers cannot be considered annual. Depending on the plant and the length of the season they may go through this cycle several times. They might self sow but the original plant will not survive into the next year. Self sowing does not make a plant perennial.

Perennials grow from seed and may or may not flower in their first season. It might seed around but the original plant keeps going. Thereafter the plant lives for several, or even many, years.

Black Eyed Susan can refer to two different genera but I assume you mean Rudbeckia. Some are annual, some are biennial and some are perennial. It depends which species of Rudbeckia you are dealing with.
gardengal48 (PNW Z8/9)
last year
last modified: last year
That is sorta right :-) A biennial is nether an annual (completes life cycle in a single season) nor perennial (lives for 3 or more years under normal care). A biennial completes its life cycle in two years, growing from seed in the first season but producing only foliage its first year. The second year it will flower, set seed and then die. The terms 'annual', 'biennial' or 'perennial' only refer to the plant's lifespan - 1, 2 or 3+ years.

Rudbeckia hirta - only one of several plants referred to as black eyed Susan - can behave as an annual, biennial or short-lived perennial depending on growing conditions and specific cultivar. Biennials generally display more flexibility in their life cycle than either true annuals or perennials, sometimes growing and flowering in a single season or living longer than 2 years. Most other species of Rudbeckia are fully perennial.

Self seeding with a biennial is usually a given - rudbeckia, hollyhocks, parsley, lunaria and foxgloves all tend to self seed very freely, to the point that once you have them planted, they will return continuously as long as they are allowed to go to seed.

ETA: typing at the same time floral was posting
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Lynn Nevins
Original Author
last year
Thank you both. Sounds like I'm 'covered' overall...that I should indeed see BES coming back every year. And I have a backup supply of new seeds just in case. And 'yes', the cultivar I have is Rudbeckia Hirta. ;-)
Lynn Nevins
Original Author
last year
So....guess what I just noticed tonight?? I was quite sure that what I had were indeed BES seedlings (that I sowed in May).

Is it possible I'm already getting flower buds??

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