En EspaŅol

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
Not Yet Rated

Saturday - January 02, 2010

From: Redway, CA
Region: California
Topic: Non-Natives, Seasonal Tasks
Title: Damage to plants after sudden freeze in Redway CA
Answered by: Barbara Medford

QUESTION:

I live on the North Coast of California near "The Avenue of the Giants" and Redwoods State Park along the Eel River. We recently have had below freezing weather, constant rain and even snow! I have beautiful Geraniums, Creeping Charlie and Hydrangeas in a large brick planter with partial shade/sun combination. They froze on the vine, turned black and look completely dead. What can I do at this point to salvage them if possible?

ANSWER:

We have been receiving many questions regarding what to do after the sudden hard freeze that occurred recently in Central Texas; in fact, we are still dipping below freezing at night frequently. Obviously, ours is not the only part of the country that has suffered from this unusual weather. One thing that applies in every case is, don't fertilize. Plants should be fertilized in the Spring, when you want to encourage new shoots to appear. The last thing you want to do is encourage new shoots now that will put more stress on already-stressed roots and probably just get frozen back again.

You may already know what happened; actively growing plants still have water in their upper structure, particularly the leaves. A sudden hard freeze causes that water to expand, bursting cell walls in the leaves, and they quickly turn dark and look pathetic. What made this freeze worse was that it was earlier than you ordinarily expect these conditions in the northwestern part of California, very sudden, temperatures went down very far, and remained below freezing for several hours. A gradual decrease in temperature over a period of time increases the ability of plants or plant parts to withstand cold temperatures. A sudden decrease in temperature in late fall or early winter usually results in more damage than the same low temperature in January or February.

We will address each of your plants with what information we have about their cold hardiness. The first thing we need to tell you is that being in a planter box, even one enclosed in bricks, is an added hazard during cold snaps.  A plant with its roots in the ground has the whole Earth insulating those roots; even if the top part freezes, the roots will have stored supplies to permit the plant to grow again. With the roots exposed to those freezing temperatures with only a few inches of soil around them, the roots may very well have been damaged also. 

To begin with your geraniums, there are 11 members of the Geranium genus native to North America, 6 native to California and 1, Geranium bicknellii (Bicknell's cranesbill), native to the area of Humboldt Co. on the northwestern California coast. See these pictures of this plant from Google; we're betting that's not what you have, right? Now look at these pictures of Pelargonium x hortorum, again from Google, and this article about them from Floridata. The Pelargonium genus is native to South Africa and has been so extensively hybridized, similar plants cannot be found growing in the wild. The Lady Bird Johnson Wildflower Center is dedicated to the use, protection and propagation of plants native not only to North America but to the area in which they are being grown; therefore, these plants fall out of our area of expertise. However, we can tell you that the Pelargonium is hardy to USDA Hardiness Zones 9 and 10. Your area of California is Zone 9. Obviously, the cold spell you had was severe enough to knock them down. In cooler areas, the Pelargonium is considered a tender perennial or an annual. Whether the roots managed to survive the cold in the exposed planter, we don't know. If you wish to take a chance that they will come back up in the Spring, we suggest you cut them to the ground and mulch to protect the roots. 

Next, to the Creeping Charlie, also sometimes called Creeping Jenny. The scientific name of this plant is Glechoma hederacea, a native of Asia and Europe. Most of the information we could find about it involved how to get rid of it, as it is considered an invasive weed, as seen in this University of Wisconsin article Controlling Creeping Charlie.  We learned it has very shallow roots in a mat right at the soil surface, which could well mean those roots are dead. 

And, finally, hydrangeas. There are two members of the genus Hydrangea native to North America, Hydrangea arborescens (wild hydrangea) and Hydrangea quercifolia (oakleaf hydrangea),  neither of which are native to California, being more plants of the Southeast, needing acidic soils which they wouldn't find in the normally alkaline soils of the American West. From the United States National Arboretum, here is an excellent article covering the cultivation of both native and hybridized hydrangeas,  Hydrangea Questions and Anwers, which not only covers many of the problems the plant may have, especially in alkaline soil, but also mentions that they are normally hardy to USDA Zone 6, so the damage of the cold should not be lasting. Again, we would recommend cutting the plants back severely and mulching against another Winter Surprise.

 

 

More Non-Natives Questions

Non-native fruit trees for eastern North Carolina
April 03, 2008 - Are there any good fruit trees to grow in eastern North Carolina? For example peaches, apples, plums? What are your recommendations? Thank you!
view the full question and answer

Planting location of non-native Japanese maple in Toronto
May 22, 2009 - Hi Mr. Smarty, I am in the region of Toronto, Canada. I just bought from nursery a "Red Select" Janpanese Maple, about 2' tall, still in its 1' pot. I intended to plant it in my front yard ...
view the full question and answer

Planting non-native sago palm and philodendron from Pflugerville TX
September 15, 2012 - I have a small/young sago palm and philodendron I'd like to plant. Do you advise to plant them now with fall/winter approaching or wait until next spring.
view the full question and answer

Smarty Plants on Pittosporum
August 05, 2005 - Need to know if "PITTOSPORUM" (TOBIRA VARIEGATA) will grow in my area of SE OK. I have purchased two of them and the nursery said that they would do great. Just needed an extra opinion. Than...
view the full question and answer

Obtaining information about non-native Maurandella antiffhiniflora seeds
February 26, 2007 - Mr. Smarty Plants: My Mother and I love to see all the beautiful Snapdragons blooming each year. We never know when to actually plant the seeds in order to have the Snapdragons come up and bloom by th...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center