Dividing Perennials

by Andrea Laine EMGV

There’s a saying among gardeners: Sleep, creep, leap.

The first year that an ornamental plant is in the ground, it sleeps. Above ground it looks like nothing is happening. All the action is underground where it is creating strong roots. A quality root system is essential for absorbing water and nutrients to deliver to the rest of the plant.

The following year, the plant creeps. We may notice new leaf buds, an elongated stem, and we are content (or relieved) that the plant is still living.

Then, finally, in its third or fourth year, the plant really starts to get showy. It leaps! There are new leaves and bold flowers. The plant is noticeably taller and/or wider and we gardeners are filled with pride and joy and our enthusiasm for gardening probably leaps, too.  

Stokesia ‘Blue Danube.’ Photo by A. Laine.

This is so true of herbaceous perennials! Before you know it, it is time to divide the perennial into smaller plants. Division can control a plant’s size and invigorate the original plant, assuring that it continues to flower abundantly. (If your perennial no longer flowers very well, that is a sure sign that it is crowded and needs to be divided.) Another benefit is that you will have new plants to place in another part of the garden or share with a friend or neighbor.

Time of year
The best time to divide herbaceous perennials is early spring, however bearded iris and Asiatic lilies prefer later summer to early fall and some plants like black-eyed Susan are so resilient they’ll accept division in spring or fall. Choose a cool or cloudy spring day or an early fall day. Dividing or planting most perennials during a hot and/or humid day, such as we tend to have during a Durham summer, is generally not advised. Also, do not divide or dig around plants the same day they have been watered.

Step-by-step guide

Step 1.  Prepare by putting in place everything you may need to complete the task: a long-handled spade or digging pitchfork, a sharp knife (I use an old steak knife from the kitchen), a full watering can or hose, and newly dug holes in the ground. If you intend to gift your divisions to other gardeners, then also have containers, a small spade and potting soil by your side.

Step 2.  Survey your plant(s). From afar, it looked like I had two giant clumps of Stokes Aster (Stokesia ‘Peachies Pink’). See photos below. They had  been in the ground four years. But upon closer inspection, notice that there are actually multiple small clumps growing close together.

Step 3. Dig and separate the plant. Use the spade or fork to dig deep on all four sides of the plant. In the case of these asters, I need not dig up the whole planting, just the smaller clumps that I wish to relocate. If the plant’s divisions are growing closely together, as may be the case with a Daylily or a Bearded Iris, you may need to dig up more, or all, of the plant. When that is the case, gently pull the division away from the original plant. Tease it with your fingers. If this is difficult, as it may be with plants that are overdue for dividing, it’s okay to cut through the clump using the knife. Just be sure that each smaller clump gets three to five shoots and part of the root system.  

Digging to divide a perennial into multiple plants. photo by A. Laine

Step 4. Replant the divisions, with proper spacing and depth (the crown at soil level), as soon as possible into your previously dug holes or at-the-ready containers. The goal is to minimize the amount of time that the roots are exposed to the drying effects of air. Water the new planting well.

As you can see in the photos above, the new divisions look a bit forlorn 10 days later. They will need nurturing equivalent to any new planting; that means vigilant watering through their first year. It is also helpful to snip new flower buds off the first year or two, if any even develop, so the plant’s energy can be concentrated on developing its root system. Remember: sleep, creep, leap!

Step 5. Pay attention to the original plant. Rebury its roots if any were exposed during the division. Enrich the soil with compost or soil conditioner. Even just loosening it will help; Plants dislike growing in compacted soil. Having some garden soil or compost on hand is helpful but not necessary. It’s okay to add the compost later in the growing year when social-distancing may not be as critical as it is this spring.

Exposed roots of Stokes aster following separation and division. photo by A. Laine.

Follow similar five steps if you wish to relocate a plant: Prepare, survey, dig, replant, nurture. I divided the asters last spring and the new plants are doing very well. I will divide and move some hostas to shadier places this year. My landscape has changed (we took down some larger trees) and the hostas are no longer planted in the right place for their needs.  

Early spring days are excellent for separating, dividing or relocating perennials. And, these are tasks you can accomplish with equipment and material already on hand. Perfect for gardeners sheltering-in-place.

1Perennials not recommended for division

  • Baby’s Breath (Gypsophila)
  • False Indigo (Baptisia)
  • Balloon Flower (Platydocon)
  • Flax (Linum)
  • Bugbane (Cimicifuga)
  • Lupine (Lupinus)
  • Butterfly Weed (Asclepias)
  • Monkshood (Aconitum)
  • Clematis
  • Russian Sage (Perovskia)
  • Poppy

Divide Only to Propagate

  • Bugbane (Cimicifuga)
  • Tall Sedum (Sedum “Autumn Joy“)
  • Garden Peony (Paeonia)
  • Yucca
  • Red-Hot Poker (Kniphofia)

Resources  

1. Some plants need dividing more often than others. Scroll to the bottom of this link for a list of perennials and their division requirements.
https://extension.psu.edu/dividing-perennials

http://chemung.cce.cornell.edu/resources/dividing-perennials

Further Reading

A glossary of gardening terms
https://content.ces.ncsu.edu/extension-gardener-handbook/glossary

The many ways to propagate plants are described in the Extension Master Gardener Handbook: https://content.ces.ncsu.edu/extension-gardener-handbook/13-propagation#section_heading_5641

December: To do in the Garden

by Gary Crispell, EMGV

How did it get to be December already? Wasn’t it 100 degrees and October yesterday? Unbelievable! So, I was looking at last year’s December calendar and I can’t think of how to improve it. Therefore, y’all get an encore! Heck, come next year it might be a new tradition.

The holidays
Are upon us.
It’s cold enough
To prune the euonymus.

Most of the leaves
Have fallen down
And into the compost
Raked and blown.

The door is closed
On the potting shed.
Most of the garden
Has been put to bed.

But before the year
Turns over anew
There are a few more things
Left to do.

Ilex x ‘Nellie R. Stevens’ Little Gem Trees CC BY-ND

Lawn
Mow the fescue
One more time.
Remove the leaves
To keep it fine.

Planting
Landscape plants
Can still be planted
There in that space
Where you’ve always wanted.

Prune
Prune the nandina
And red-berried holly.
Arrange them on the table
To make it look jolly.

Herbaceous perennials
Can still be cut back.
While weeds and “bad” trees
Can be thoroughly wacked.

Spraying
While some of us think
Spraying is fun
In the month of December
There should be none.

Other Stuff That’s Mostly Fun
The Christmas tree
Really needs water
And will appreciate
Being away from the heater.

To keep your poinsettias
Cheery and bright
Put them in the room
With the sunniest light.

As to your soil recommendations
Apply the lime.
Save the fert
For the warmer springtime.

If it’s viticulture
Or an orchard you seek
Order plants now
To plant by March’s second week.

For your strawberries
A sweet straw bed
Either wheat or pine
A blanket for their heads.

May your holidays
Be blessed and merry
As bright and cheery
As the holly’s berry.

And may next year’s garden
Be like my Grandmother’s
A bounty for you
And a bounty for others.

Further Reading
December is a good time to explore the NC Extension Gardener Plant Toolbox: https://plants.ces.ncsu.edu/

Getting Back to Basics

September is synonymous with school. So, this week we are getting back to basics with a post that defines foundational gardening terms. The better you understand these terms and phrases, the easier it will be to identify, select and care for plants in your landscape.

Growing season:  The period between the beginning of growth in the spring and the cessation of growth in the fall.

Hardiness zone:  Expressed as a number and letter combination from 1a to 13b, the US Department of Agriculture has assigned a zone to every geographic area of the United States based on the average annual minimum winter temperature. Tags on plants sold commercially often identify the zone(s) in which the plant will grow.   

Microclimate. Climate affected by landscape, structures, or other unique factors in a particular immediate area.

N-P-K:  Acronym for the three major plant nutrients contained in manure, compost, and fertilizers. N stands for nitrogen, P for phosphorus, and K for potassium.

Coreopsis major, blooming along roadsides now, is a native perennial hardy in zones 5a to 9b. It attracts butterflies and songbirds and is deer resistant. The flowers are large (for coreopsis) and the stems are tall. Photo by A. Laine

Annual: Plants started from seed that grow, mature, flower, produce seed, and die in the same growing season.

Biennial: Plants that take two years, or a part of two years, to complete their life cycle. By freely reseeding, a biennial plant may seem to come back year after year, but you are actually seeing new plants.

Perennial: A plant that lives more than two years and produces new foliage, flowers, and seeds each growing season. Tender perennial:  A perennial that is not tolerant of frost and cold temperatures. Applying a winter mulch can help it survive It may die off above ground and regrow from the roots.

Woody perennial: A plant that goes dormant in winter and begins growth in spring from above-ground stems. Herbaceous perennial: A plant that dies back in the winter and regrows from the crown in spring.

Exotic: A plant of foreign origin or character; not native; introduced from abroad, but not fully naturalized.  Naturalize: The process whereby plants spread and fill in naturally.

Native plant: A plant indigenous to a specific habitat or area. Nativar: A plant that is a cultivar of a native plant. Cultivar: A cultivated variety of a species. Propagation of cultivars results in little or no genetic change in the offspring, which preserves desirable characteristics.

Integrated pest management. A method of managing pests that combines cultural, biological, mechanical, and chemical controls, while taking into account the impact of control methods on the environment.

Invasive. Growing vigorously and outcompeting other plants in the same area; difficult to control.

Noxious weed. Weeds that have been declared by law to be a species having the potential to cause injury to public health, crops, livestock, land, or other property. Noxious weeds are very invasive. There are 124 plants in NC that meet the legal criteria.

When a gardening term has you stumped, refer to the glossary chapter of the Master Gardeners Handbook for a definition – there are hundreds of entries — and a small dose of continuing education.

— A. Laine

Resources & Further Reading

Glossary Chapter of Master Gardener Handbook: https://content.ces.ncsu.edu/extension-gardener-handbook/glossary

Find your plant hardiness zone:  https://planthardiness.ars.usda.gov/
USDA Plant Hardiness Zone Map, 2012. Agricultural Research Service, U.S. Department of Agriculture.

Noxious weeds in NC: https://plants.usda.gov/java/noxious?rptType=State&statefips=37

https://plants.ces.ncsu.edu/plants/coreopsis-major/

Growing Well in the Garden

It’s August and my garden (and myself) are showing signs of weariness. So I turned to my fellow Extension master gardener volunteers to find out what is growing well in their gardens. There are plant picks and care tips in the vignettes that follow to inspire us all; and if too late for this year, then definitely for next year! All photos were taken by the master gardeners.  — Andrea, Blog editor

Missouri Primrose

I seeded these indoors in early 2018 and planted outdoors after April 15th in 2018. For the past six weeks I have awakened to new blooms every morning and they have exceeded five feet in height. As a bonus the solitary pollinators sleep in them at night to be ready for the morning harvest! Missouri Primrose will have a perpetual place in my garden. – Brandon W.
 

Caladium and Coleus

My front porch plants are doing well. I have been planting caladium and  coleus every summer for 30 years. I love the combination and it also goes really well with the pink knockout roses in front of my porch. I think this year I will try to save my caladium bulbs for the first time ever. — Kerry H.

Coral bells and hostas

Coral bells (Heuchera sanguinea) loves the shady side of my house. It has thrived in this spot for about five years and never fails to surprise and delight. It’s an evergreen plant with maximum height of a foot-and-a-half and a spread of slightly less. The hostas are doing well, too!  — Carol T.

Zinnias

Almost all of the plants in my garden are perennials. For the first time since I was a child living in hot and dry Texas, I decided to plant Zinnia seeds this year- as a nod to a childhood long past. Thank goodness I did; It is practically the only flower blooming along the edges of my mostly shade garden. It is definitely drought tolerant and deer resistant and planting them will make every child feel like a successful gardener! Also, it is a simple delight to see what color might unfold on top of their tall  sturdy stalks during the course of this hot dry summer.  — Cy G.

Agastache

Both Agastache foeniculum (anise hyssop) and Agastache rugosa ‘Golden Jubilee’ are in this photo. I wish you could see the multitude of bees and butterflies that are feeding on the spiky blooms. Throughout the blistering heat wave, these plants have been alive with pollinators. This is my second year with them. They get a bit “floppy” late in the season, so I’m going to try aggressive deadheading this year and see if I get more new growth and less flop. During the hot, dry weather I make sure they get one good soaking a week. — Tina F.

Cleome

Cleome or spider flower (Cleome hassleriana) is a fragrant, sun-loving annual. Mine are still growing tall, producing blooms and lots of seeds. – Cathy L.


Lesser known

Solomon Seal (Polygonatum spp.) on left, is a native herbaceous perennial that grows well in shady areas. Quarter-inch blue-black (poisonous) berries dangle from the stem in the fall. Pictured here is one with variegated leaves. Weeping love grass (Eragrostis curvula), on right, is an ornamental grass whose leaves turn yellow to bronze in winter. It is used as erosion control on highway right-of-ways. – Beth A.

Learn more about the characteristics of each of the above mentioned plants at https://plants.ces.ncsu.edu.

Fennel

Year after year our bronze fennel is host to swallowtail caterpillars. Since rethinking our lawn care routine, the fennel has a bigger following than ever with a variety of bees, other insects and even a praying mantis who’s motives might be suspicious. The fennel is easy care with an occasional drink and it readily reseeds to keep the patch going strong. — Lynne N.

Beginner’s Luck?

My gardening interests are primarily focused on creating an aesthetic and pollinator friendly landscape, along with a few herbs. This year I decided to try a tomato plant. I bought a golden tomato shrub plant at the farmer’s market. It is doing so well! I’ve lost two tomatoes to blossom end rot, but have harvested a dozen already and have 30 more on the plant.  — Kerry H.

Tomato ‘German Johnson’

Here is one of my German Johnson tomatoes, a really sweet, pink variety. I planted some in the garden and put one plant in my homemade self-watering bucket. I really like the self-watering bucket. All month (July) I have had tomatoes. This is the first time ever I have had an indeterminate really continue bearing. It is eight feet tall and blooming. I think having uniform moisture is the best thing about the self-watering bucket. – Linda D.

Coming up on Thursday, more “Growing Well.”

Ten Plants That Can Take the Heat

by Andrea Laine, EMGV

Come July, I am unlikely to be outdoors — much less gardening—unless watering or weeding is absolutely required. I dislike the heat of a North Carolina Piedmont summer. Luckily for my garden and the birds and insects who visit it, there are perennials and annuals that do just fine despite the heat and even when rain is not plentiful.  

I’ve been noticing those plants more lately as it has been almost two weeks since a measurable amount of rain has fallen on my garden. And, we’ve had some very hot days, with heat indexes of 100 or more. I watered six days ago and again this morning (July 20).

Plants begin suffering physiological damage at 86 degrees and above1. Keeping up with watering is important, especially for the newer additions to the garden or those recently transplanted. An established tree, shrub or plant will fare better due to a stronger, more settled root system.  

Here are 10 plants that tolerate sunny, hot, and dry conditions reasonably well:

Perennials

Blackberry Lily or Leopard Flower (Belamcanda) This is my first experience with this semi-hardy summer bulb. It prefers morning sun, but this plant is doing very well in afternoon sun in well-drained soil. The dainty flowers began blooming in July atop stalks 30 to 36 inches high. Blackberry refers to the black seeds that follow flowering. Store corms in dry sand at 35-41 degrees.


Catmint (Nepeta ‘Walker’s Low’) This is another plant I had never grown before this year and so far I am very pleased. Lavender spikes of flowers (10 inches high) appear late spring to mid-summer and flowers are always crowded with bees, moths and butterflies. It is deer resistant. Photo credit: Debbie Roos


Lantana (Lantana Camara) The ‘Miss Huff’ cultivar is a generally reliable perennial in the Piedmont region of NC. Treat all other cultivars as annuals here. Miss Huff is a woody evergreen shrub that will grow 4’ high and wide in full sun. It blooms from late spring to fall and flowers are a mix of orange, yellow and pink. Cut it down to four to six inches in the spring before new growth begins.


Garden Sage (Salvia Officinalis) This plant is the star of my herb garden – good-looking, evergreen and productive all year. It is planted in well-drained soil and receives four to six hours of sun; that’s about as ‘full’ as my heavily wooded property allows, but obviously it has been good enough for this plant.  


Purple coneflower (Echinacea purpurea)  Being native to the southeast United States, it’s not a great surprise that the purple coneflower tolerates heat and drought. But it also tolerates humidity and poor soil and can grow in full sun or part shade. Pinkish-purple flowers appear from May to October. It is deer resistant, too. Photo credit: https://plants.ces.ncsu.edu/plants/echinacea-purpurea/

Annuals

Summer snapdragon (Angelonia angustifolia)  For years now I have relied on this annual to add color and grace to my front walkway. I choose white and purple flowering cultivars but there are pink and variegated ones, too.  It grows at a medium rate and flowers from June through September. I bet it would do well in a container. Actually, most plants that tolerate drought probably would.


Begonia x ‘Dragonwing’ This has long been my favorite begonia because it fills out so nicely. I don’t readily think of begonias as being heat and drought tolerant, but I’ve included this one because of my firsthand experience with it under exactly those conditions. I love its drooping clusters of flowers. I usually plant this in a container on my deck which receives morning sun. This year I put it in the ground outside my front door,  a western exposure that also receives a good bit of shade. As you can see, it is doing well.


Evolvulus  glomeratus ‘Blue daze’ It was serendipity when I spotted this plant in a nursery in Mebane last summer. I was through with my planting for the season (or so I told myself) but just couldn’t resist its charms. I do like plants with blue flowers. I brought it home without knowing anything about it. I put it in the ground in full sun among some perennial grasses and it proceeded to take over! I eventually learned that it is a ground cover in the morning-glory family. It’s flowers close at dusk or on cloudy days. If planted in the ground, it forms sprawling mounds nine to 18 inches tall2, which was precisely what I experienced. I would plant it again, but in a more open space. It was yet another lesson in “right plant, right place.” Photo credit: JC Raulston Arboretum


Mandevilla (Dipladenia sanderi) Every summer my mother planted this tropical vine in a container (with trellis for climbing) on her deck in Southeast Pennsylvania. In a short time, it looked spectacular. I’ve often considered doing the same, but the vines have become more expensive than I care to spend for a one-season plant. So, imagine my glee this spring when I noticed a new compact mounding cultivar for $6 in a big box store. I planted three in the ground; I mulched but have not been aggressive with water. They attract hummingbirds and butterflies. NC State Extension says they can be wintered indoors in a container.  


Portulaca grandiflora This is an old favorite of mine that I have not planted in a great while but is such a crowd pleaser. I think it might come to own this sloped spot (therefore, well-draining) among the native pink muhly grasses. There are varieties that flower in a single color, but I enjoy the ones with a variety of colors on one plant. So cheerful! Like evolvulus, the flowers close on cloudy days.

I’ll be looking to add more of these plants to my garden in future years. I am so grateful that some like it hot!


Footnotes, Resources & Further Reading

1. https://www.ahsgardening.org/gardening-resources/gardening-maps/heat-zone-map

2. https://plants.ces.ncsu.edu/plants/evolvulus-glomeratus/

https://extensiongardener.ces.ncsu.edu/extgardener-salvias-for-the-sage-gardener/

https://www.uaex.edu/yard-garden/resource-library/plant-week/begonia-dragonwings.aspx

Learn more about other plants listed above: https://plants.ces.ncsu.edu/

Unless otherwise noted, photos taken by A. Laine