Scraggly Nandinas

Question: My Nandinas are looking pretty scraggly after a fairly mild winter. Is this a good time to prune and how much can I prune at one time?

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied March 14, 2023, 9:44 AM EDT
response: It may be best to wait until the plants start producing new growth later this spring; that way, you can tell which bare stems are dead versus just temporarily leafless due to winterburn. How much to prune will depend on the amount of potential dieback, but in general it's best to avoid removing more than a third of a shrub's total branch volume any given year. Nandina are pretty tough plants though (to the point where the species can be invasive) so it's unlikely an established plant would not regrow satisfactorily even if pruned much more drastically on occasion.  Miri

responder: The Question Asker Replied March 14, 2023, 4:26 PM EDT
response: Miri, thanks for the advice. How are Nandinas invasive? I've not seen any signs of mine spreading.   On 03/14/2023 9:44 AM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied March 14, 2023, 5:07 PM EDT
response: Invasive plants ironically don't always appear in a weedy fashion in the same yard they are planted, but are capable of spreading into natural areas where they out-compete native vegetation and don't support local wildlife. Several, though not all, Nandina cultivars produce berries that birds (and possibly other animals) consume, dispersing the seeds as they travel. The Maryland Department of Agriculture Plant Protection Section [see link for the explanation of this program] uses weed assessment tools to designate certain plant species as invasive; they included Nandina domestica on that list a few years ago. Its designation is a Tier 2, which means nurseries and landscapers can still sell and install the plants but must inform customers of its invasive potential.  While some Nandina cultivars produce few or no berries, to our knowledge no cultivars are presently exempted from that status on the list. (Gardeners are not required to remove existing plants.) The plant you pictured appears to be one of the effectively-sterile varieties (it looks like 'Firepower'), so while it may pose little risk of spreading by itself, it still is probably vigorous enough in constitution to withstand heavy pruning if it's needed/desired to refresh its appearance. We've seen lots of instances of winterburn so far this winter, on a variety of hardy evergreens, probably due to the wild temperature swings we experienced earlier in the season.  Although Nandina is not currently a major problem in the state (a few counties have recorded escaped populations in natural areas), the MDA is likely having to prioritize and target species with a potential to spread widely if unregulated, since other invasive plants long established and widespread in Maryland (English Ivy being a notable one) are not yet on the tiered invasive list.  We have several web pages about invasive species (plants and otherwise) if you're curious to learn more. The page Invasive Plants to Avoid Buying is more gardening-specific, for example.  Miri

responder: The Question Asker Replied March 15, 2023, 10:08 AM EDT
response: Thank you for this important information. None of my Nandinas produce berries and I will certainly not buy any more, if I feel I need to replace them.     The only problem of invasive plants I find in my planting beds and lawn is English Ivy sprouting everywhere. Someone told me that seeds (which I didn't know English Ivy produced) are in my mulch. Does this sound like a reasonable explanation?   On 03/14/2023 5:07 PM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied March 15, 2023, 10:38 AM EDT
response: It's possible birds or other wild animals are moving the seeds around and depositing them onto the mulch (especially if they are using a nearby bird feeder and therefore hanging around longer). It's probably not the case that ivy seeds came in a contaminated delivery of bulk mulch (or bagged mulch), but we can't rule it out.  English Ivy flowers and then produces berries once it's mature enough, and typically only when it's climbing a surface (tree trunk or wall). At that point the foliage doesn't always have the characteristic English Ivy shape, so people might not recognize it for what it is. If you're curious, you can view images of flowers, fruits, and other aspects of the plant on the species' page in Maryland Biodiversity Project's website.  Miri