Native Plants

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Tuesday - June 07, 2011

From: Valley Forge, PA
Region: Mid-Atlantic
Topic: Wildflowers
Title: Planting ironweed in Valley Forge
Answered by: Anne Bossart

QUESTION:

I work in a national park and we have one population of Vernonia glauca (tawny ironweed), a state-listed endangered species in Pennsylvania. Last year we collected seed and have been successful in growing them this spring in order to establish several satellite populations. Can you advise on when the best time to plant these small plugs would be (or if we already missed it?)and what the latest date they can be planted and expected to do well might be?

ANSWER:

I am not sure we can help you, as our answer is "it depends ...".

It depends on how big the plugs are and if they will be planted in a place where they can be watered until they are established. If that is the case, you can plant them now. If you are depending on Mother Nature to rain on them, you may have missed your window of opportunity. When I lived in your area, my personal deadline for digging up and dividing perennials was Memorial Day ... after that I only planted container grown perennials and annuals.

So ... if you can water them until they establish (they don't "flag" if they aren't watered) then go ahead ... if you are unsure, maybe plant half of them, pot up the rest and keep them going and plant them in mid to late September when the heat lets up but the ground is still warm. This will give them the opportunity to establish roots quickly before dormancy.