Wednesday, September 11, 2013

Where Did My Foxgloves Go? Over-wintering Tender Perennials; USDA Hardiness Zone Map; Swallow-worts

Foxgloves 2012

Where did my Foxgloves go? Biennials

Have you ever planted foxgloves (digitalis) only to have them die out the following year? When you go to a nursery to buy perennials you could possibly be buying biennials and not know it unless they are marked as such on the label. Some of the more popular biennials are: Foxglove, Sweet William, and Hollyhocks. A biennial is a plant that usually only lives two years versus a perennial that will live multiple years (most of the time). The first year a biennial will come up from seed, and form leaves and develop its roots. The second year the plant comes up, grows its leaves, flowers, produces seeds and usually dies after that season. Sometimes they might live another year or so. There also is a perennial form of foxglove, Digitilas grandiflora (yellow). 

The important thing to know about biennials is that if you want them to come back every year, you can't cut them back or pull them out after they are done blooming. You need to let the flowers and seeds DRY on the stalk and remain on the stalk until they are thoroughly dry. 

Dried seed pods on Foxglove.
This may appear quite unsightly (see photo of dried seed pods), but it's usually the only way you will always have a continuous supply of those specific flowers. Unless of course you want to purchase the seeds or plants every year. I have been growing our foxgloves and Sweet Williams for about twenty years using this method without purchasing any plants or seeds. When your new seedlings come up the following year you can transplant them to other areas of your garden or share with friends. After the seed pods are dry, I like to cut off the top stem of the foxgloves and sprinkle the seeds around other areas of my yard where I would like the new plants to come up. Also, you do not have to cover the seeds up with soil or compost. Hollyhocks will produce seeds this way as well, but if the original seed or plant was a double-flowering  hollyhock the seedlings most likely will not be a double flowering hollyhock but a single.

Another important fact about foxgloves is that they are poisonous. Foxgloves are the source for the heart drug (digitalis) which is poisonous in the event of an overdose. The plants are not poisonous to touch, only if it is ingested.  Some people might be more sensitive to this plant than others, but most people that I know that have this flower in their gardens have never had a problem with it.

More information on foxgloves:

Sweet William 2013
You can use this same method of self-sowing seeds for other perennials that you would like to re-seed such as columbine, rose campion, yarrow, Black-eyed Susan, and purple coneflower.  Perennials you should not let go to seed would be any hybridized plant. A hybridized plant is a plant that has parent plants that have been crossed pollinated with a different variety of the same plant. An example might be for different colors, stronger stems, taller plants, disease resistance, etc. If you let them go to seed it is possible that they will produce seeds quite different from the parent plant. An example of these hybrid plants would be the many varieties of daylilies.

Here is a Link to definition of hybridized plant: What is a Hybrid Plant

Coleus from my friends' garden (Mark & Linda Adams)
Overwintering Coleus

If you purchased some of the newer strains of coleus you might want to try bringing some of them indoors for the winter. Coleus is not hardy in our temperature zone (northern New York). They are very easy to over-winter inside. You can cut some side shoots off of your plant now (early September), remove the lower leaves, and bring them inside and put them in a container of water. They will need bright light, but not direct sunlight until they are potted up. Once they root, then you can plant them in a potting mix. Or if you prefer, and have a lot of room to store them, you can dig up the whole plant, pot it up and bring inside. Don't wait too long to bring them in or start cuttings because the first cold weather or light frost could kill your plants. Here is a link for more information on over-wintering your coleus: Info on overwintering your coleus

Here is a link to other plants that are not hardy in the northern climate and how to  store them for the winter (calla lily, caladium, canna, dahlia, Elephant's ear, gladiolus, and tuberous begonia). And at the bottom of this site are links to overwinter your geraniums and fuchsias: Overwintering Tender Perennials 

Peony, Seiboldiana Elegans Hosta, Climbing Hydrangea,
Sundrops, Foxgloves

Purchase Plants that are Labeled for your Temperature Zone

When you are looking for perennials to plant around your home be sure to check the labels on the plants for your hardiness zone. Some plants are sold in local stores that are probably not suited for your/our climate. And at the same time, you might have some micro-climates in your yard that will tolerate some more delicate plants. Also for me, it's trial and error as well. I've tried plants that were zoned for our area such as scabiosa and gaura and have lost them (I'm assuming because of our cold winters) so I just gave up on them after several tries.

To find out your hardiness zone here is an excellent Link to the US Department of Agriculture Plant Hardiness Zone:
You can click on each state to get your county and hardiness zone.

This is a link to Northern Gardening Guide to Hardy Perennials: Northern Gardening Plant Guide  The guide gives the lowest zone that a specific plant will tolerate.

Invasive Plants

Swallow-worts  Photo by Ted Link
Black and Pale Swallow Worts

"In New York state, swallow-worts pose a particular threat in alvar(*), where they out-compete a number of rare plant species and disrupt nesting by grassland birds. In general, insect diversity and abundance is significantly lower in dense stands, with cascading effects on the entire food chain." Michigan Department of Natural Resources, Michigan Natural Features Inventory, 4/2012 
* Alvar= commonly found near northern Great Lake shores where flat bedrock pavement is exposed.

Both the Black and Pale species of Swallow-wort develop pods that look like milkweed. They are very toxic to the monarch butterfly larvae and to livestock.  If the monarch butterfly lay their eggs on this plant the larvae will die.

Areas of known infestationSwallow-worts have been observed in nearly every county of New York, though a distinct epicenter exists in Jefferson County, where immense stands (100 to 500+ acres) of pale swallow-wort can be found on Grenadier Island and Stony Point in the town of Henderson. The plant is also established in the townships of Adams, Antwerp, Brownville, Cape Vincent, Clayton, Ellisburg, Henderson, Lyme, Orleans, and on Fort Drum.
Swallow-wort has slowly progressed outward from this epicenter. Management efforts are focused on preventing the spread toward Tug Hill and the Adirondacks and are therefore focused on Oswego, Lewis, and Oneida counties.    St. Lawrence Eastern Lake Ontario Partnership for Regional Invasive Species Management

Here is a link for the St. Lawrence Eastern Lake Ontario Partnership for Regional Invasive Species: Black and Pale Swallow Wort

It is recommended that if you come upon swallow-wort that has matured and has ripened seed pods like the milkweed, to stay out of it because you could actually end up spreading the plant to new, uninfected areas if you have the seed on you. If you have this plant on your property and would like to get rid of it you can mow it down when it is young. If the pods have matured, remove the pods before they open and burn them. Continually mowing the area will keep it under control.

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Early morning photo by  Ted Link


  1. great blog! I just love the pictures! Tell Ted super job....the best is the barn in the mist! :)

  2. Thank you Martha! I appreciate your comments and will share your message with Ted.

  3. Hi Sue, Got in but how do I know when new postings are up for viewing? I have an area where I want to naturalize with biannual and perrenials so I am taking the seed pods from my foxglove gloriosa daisy and coneflower and scattering the seeds on the long grass that is there now in hopes the rain etc.will get it to the ground so they will germinate next spring. Hopefully the plants will be lost on the grass so Bambi and family won't see them. Fight noe there is queen Anne's lace, goldenrod and extra day lilies growing there. I want things in there for color so anything the deer won't eat is a good thing. I have mowed a path through that area which I plan to keep there through the years. It is just a fun spot for me. That's about it as another thunder storm is overhead. Judy

  4. Hi Judy, There is a link at the top of the page that says "Follow By Email" and you can sign up there. Also, you can see the previous posts by scrolling to the bottom and clicking on "Older Post". Your plan for scattering your seeds should be nice. Sounds like a good idea, and the deer won't eat the Foxgloves because they are poisonous.