Skip to content
Elisabeth C. Miller Library

Keyword: Vegetative propagation

Nandina pruning and propagation

I have a Nandina (heavenly plum blossom) that is getting really top heavy and I need to find out how to divide it or cut it back and root the cuttings. I’ve been reading up on it and there is very little information about propagating them.

 

The book American Horticultural Society Plant Propagation by Alan Toogood (1999) recommends
taking nodal greenwood (similar to softwood) cuttings in the summer. The shrub
can also be propagated by division but this is recommended in the early spring
and not in summer due to the increased risk of wilting and scorching.

Rainy Side Gardeners in the Pacific Northwest notes that fresh seed (as soon as it is ripe) can be germinated in six to eight weeks. Old seed may take up to two years to germinate. Semi-ripe cuttings can be rooted in the summer.

As for pruning the Nandina, the American Horticultural Society Pruning and
Training: A Fully Illustrated Plant-by-Plant Manual by Christopher Brickell and
David Joyce (1996) suggests that plants can usually be renovated by cutting back
old canes to ground level in the early spring when the older leaves have turned
from red to green. Rainy Side Gardeners suggest cutting the oldest canes down to
the ground, discouraging the shrub from getting top heavy and falling over. The
pruning will keep it growing a denser growth lower down on the shrub.

A Practical Guide to Pruning: How and When to Prune for Better Shrubs, Trees,
Fruits and Climbers by Peter McHoy (1993) suggests cutting one out of every
three canes to the ground. His recommendation is not to do this each year.

Paghat’s Garden (a website maintained by a local gardener) had this to say:

“Nandina thrives in considerable shade, but has a tendency to become leafless underneath unless it can get sunlight around the lower part of the plant.
Before I transplanted this one, it was in a lot of shade, & needed to be staked
because it became top-heavy. This did not necessarily harm its looks, because
the species’ tendency to lose leaves at the bottom gives it the appearance of a
miniature tree with long trunk, & I used the “empty” space around its base for
small ferns. But when transplanted to a sunnier garden, it became more broadly
bushy & the trunk became stronger, no longer needing to be staked.”

,

Snowdrop buds won’t open

I planted some Galanthus ‘Flore Pleno’ three years ago. For all three years, the foliage comes up, buds form…..and then nothing. The buds swell and begin to color, but they never ‘drop,’ and will remain on the plants for up to two months without change. They never open, but very gradually become desiccated. They do not turn brown like daffodils with bud blast, and I see no signs of fungal disease. The foliage appears totally healthy. They are planted in a north facing bed, soil is medium-heavy but not waterlogged. I have done research but have found no explanation. Any thoughts are appreciated.

 

A general article by Christopher Lloyd on snowdrops in The Guardian (2001) makes a brief mention of heat causing bulbs to go blind (i.e., not flower), but this is said in the context of growing them indoors. Lloyd also mentions that Galanthus bulbs “are at their happiest in a clay/humus-rich soil that will be damp in winter and spring and dry during the summer.” They do not thrive in soil which is too rich or too acidic.

Another possibility is that you may need to divide them. Seattle’s Dunn Gardens has a helpful care sheet for growing snowdrops. Here is an excerpt:
“In the garden snowdrops do best in a partially shaded situation. If you have a very sandy, free-draining soil, amend it with compost. They love damp ground especially in the winter/spring. After the plant has finished flowering, allow the foliage to fully die down on its own. Do NOT cut the foliage off early, nor twist or braid it. Yes it will be ugly, but if planted around later emerging perennials, it won’t be so offensive.
“The Narcissus fly is the bane of snowdrops. After flowering, the fly will lay eggs on the foliage. The eggs hatch and the maggots will eat their way down into the bulb, destroying it. We’ve found that siting this bulb, where it gets afternoon or full shade after flowering, greatly reduces the chances of infestation. There is little in the way of chemical control, and what there is, is nasty.
“To bulk up galanthus, liquid feed after flowering, with a half strength solution of a water-soluble fertilizer, every two weeks, until the foliage has died down completely. If you
notice that the clumps are becoming congested (bulbs are starting to push up out of the ground), divide immediately after flowering.”

I recommend Naomi Slade’s book, The Plant Lover’s Guide to Snowdrops (Timber Press, 2014). In it, she describes in great detail the Fibonacci series by which snowdrops multiply: some varieties do this quickly, others slowly, in a mathematically governed sequence. The result of this natural system of propagation is that you will eventually have a dense clump of snowdrops that needs splitting up every few years if the bulbs are to have sufficient resources to produce flowers.

, ,

Dividing and transplanting lilies

I have a question about what is the best time of year to transplant and
divide Asiatic lily bulbs? Is it fairly easy to identify where the bulb
should be divided? Also, someone told me to use a rooting solution on the
divided bulbs. Is this necessary? Is late October too late in the fall to divide
them?

 

Most sources say to divide lilies in the fall. You do not need to use a
rooting solution on the divided bulbs. Sunset’s Western Garden Book
(2001) says the following: “If clumps become too large and crowded, dig,
divide and transplant them in spring or fall. If you’re careful, you can
lift lily clumps at any time, even when they are in bloom.”

One rationale for lifting them when in bloom is provided in an article
from the Wisconsin Regional Lily Society, no longer available online, but excerpted here:

“After three successive years of making this futile pact, I finally
concluded that books were wrong! Fall isn’t the time to transplant
lilies. It’s a job best done in mid-summer when they’re in full bloom.
This eliminates most of the guess work, since at this point, the plants
are at their maximum height, making it nearly impossible to make the
mistake of planting the tall ones to the front of the border, the short
ones at the back. It also affords a crystal-clear picture of concurrent
bloomers. In fall, no matter how carefully one does the job, when digging
dormant bulbs at least one bold orange always manages to get itself
placed directly beside the brightest pink. The clashing colors burn
themselves into your retinas nearly as well as flashbulbs-blink quickly
and the image reappears!

“The maximum size of the plants in mid-summer is another advantage. When
autumnal plants have shrunk to a mere fraction of their former selves,
it’s too easy to misjudge your space placement. Who hasn’t heard the
disheartening ‘crunch’ of a spade slicing through the most expensive bulb
in the bed? How it knows the price, I’ll never know.

“Spring is the only time I’d actually refrain from moving lilies. The
delicate new shoot is easily broken, and once gone, the poor bulb has
only two options: It will either die or spend an entire year below
ground, depleting its energy reserves as it forms a new shoot for the
following spring. All the while it’s caught in a perilous game of Russian
roulette. Without aboveground parts to warn of its existence, it can
never quite be sure when a spade might suddenly come slicing down.
Crunch! -The second most expensive bulb gone?

“Certainly no plant will be thrilled at being dug up and moved in full
flower, but if it’s kept well watered and blooms are removed, almost any
perennial will have recovered fully by the following season. One of the
best gardeners I know says that the best time to move any perennial is
when you have the time!”

, ,

Dividing and transplanting iris

When is the best time to divide and transplant Irises? I have Japanese, bearded and yellow flag (I think) irises.

Rhizomatous irises (the kinds you have) are best divided in midsummer:

Lift rhizomatous kinds, such as bearded iris, in midsummer and cut rhizomes into sections, each with roots and a fan of leaves; replant, with tops barely covered, 6 inches apart. Flowers will be sparse the next year, but good thereafter.
(Source: American Horticultural Society Plant Propagation, ed. by A. Toogood, 1999, p. 202)

“The optimum time..is six weeks after flowering. This is usually in midsummer, allowing time for the new rhizome to become established and make sufficient growth to produce fans to flower the following year. New roots that began growing immediately after flowering will then be strong enough to help anchor the new plants. Early spring is another suitable time, just as the other main period of root growth is about to start, but flowering may be forfeited, and if flowers are produced the stems will almost certainly need staking. Bearded iris cultivars are tough, and if the rhizome is large they can survive out of soil for many weeks. This is not an ideal situation, but it makes transport of the plants easy.”
(Source: The Gardener’s Guide to Growing Irises, by G. Stebbings, 1997, p. 93)

Good instructions can be found in these articles:
Digging, Dividing, and Replanting Bearded Irises
Garden Experiences: Dividing Bearded Iris

, ,

Dividing Calla lilies

Can I divide my Calla lily? When should I do this?

According to Sunset Western Garden Book (2007), Calla lily (Zantedeschia) should only be divided if it shows signs of decline. The Royal Horticultural Society suggests dividing in spring, if needed:

“Propagate by division, in spring. Small rhizomes that have been overwintered in pots under cover can literally be cut up into sections, each with a visible bud.

Large overwintered clumps in the garden can be divided in the same way as other perennials, by lifting the plant before there is much top growth, and chopping through the roots with a spade and dividing into smaller sections.”

Moving and dividing hydrangeas

I have a very large hydrangea that has been in the ground at least 15 years. I’d like to move it, and have heard that it can be divided into several bushes. Are there any special details I should consider when performing this task?

I found a reference to the technique you describe in Hydrangeas: A Gardener’s Guide by Toni Lawson-Hall and Brian Rothera: “DIVISION. Sometimes, when moving a large H. macrophylla cultivar, the plant falls apart during the operation. It has been found that, provided each section has good roots, planting the separate pieces is totally successful.” This is similar to the process of layering, where branches are nicked and then pinned down into the soil to allow roots to form, and then severed from the parent plant with a sharp shovel six months to a year later. The small plants will be genetically identical to the original plant.

dividing Phormium

Can I divide New Zealand flax without killing it? When should I do it? My adult plant, about three years old, has two very healthy looking youngsters that I would like to move.

The best time to divide Phormium is spring, according to American Horticultural Society’s Plant Propagation (DK Publishing, 1999), but what you are describing are new offsets, so you will not be splitting the entire crown of the plant, but instead separating them from the parent plant. Wear gloves when working with Phormium. You may be able to use two garden forks to separate the youngsters from the parent.

propagating yew from cuttings

I planted a Taxus baccata ‘Fastigiata’ roughly 10 years ago and it grew to about 1.5m. Unfortunately it was cut down by mistake. Is there any way I could take a cutting from the tree or some way to preserve any part of it? It holds great sentimental value.

According to The Complete Book of Plant Propagation, edited by Charles Heuser (Newtown, CT: Taunton Press, 1997), your yew can be propagated by cuttings, but it is recommended that the cuttings be taken in fall. It’s worth a try to take some now, though, since the tree is already cut. You want upward-growing, semi-ripe cuttings (that is, there should be some bark at the base and some green stem at the tip), and they should be pulled off with a downward motion so that you get a “heel” of bark from the main shoot. Treat them with rooting hormone and place in a pot somewhere where it can remain cool and moist for several months. Take plenty of cuttings to increase your chance that at least one will survive.

American Horticultural Society’s Plant Propagation, edited by Alan Toogood (New York: DK Publishing, 1999), has more specific suggestions. They suggest a 4-6 inch cutting from 1-3 year old wood that is still green at the base.

If your yew made seeds, you might try planting them, but it takes a long time for them to germinate and grow from seed. To grow from seed, the AHS Plant Propagation recommends mixing the seeds with damp peat or sand and keeping them at about 68 degrees for 4-6 months, then at 34 degrees for 1 month before planting. If the seeds germinate in late summer, though, they won’t be ready to winter outdoors that year. For this reason, the AHS also suggests simply sowing the seeds outdoors and waiting for germination in 1-2 years. If you do this, be careful not to lose your sown seeds while waiting for them to grow!

propagating lilies by stem bulblets

My Easter lily died, and as I was removing some of the soil I saw a small green bulb (less than an inch long). The tag that came with it said they can grow year round, and I live in Florida where it always stays warm enough. I decided I wanted to try to salvage that bulb and regrow it. Can I safely remove that bulb from the stem of that dying plant and replant it?

I also have recently planted some small Asiatic lilies (which are growing like mad, I planted the bulbs less than a month ago and they are already over 6 inches tall!) and want to be able to do the same when they die. I hope you can help me out, I love lilies and want to be able to keep these going and then add more and more. Thank you!

The Complete Book of Plant Propagation (edited by Charles Heuser; Taunton Press, 1997) gives these instructions for growing on “stem bulblets” like what you see on your Easter lily (Lilium longiflorum):

“Pick off the bulblets carefully, to avoid damage to any small roots that may already have formed. Plant bulblets at twice their own depth in a prepared pot a layer of sand. …Grow on in a cold frame [I guess that would be outdoors for you, but shaded]. The following fall, pot up individual bulbs separately, or if growth has been vigorous, set … in
the flowering site. …will take 2-5 years to flower.”

The same process should work for your Asiatic lilies (Lilium hybrids), if you have stem bulblets there, or you could try “scaling.” Scaling involves breaking a bulb into individual scales, throwing out any soft or wrinkly ones, and bagging them up in a sand/peat mixture (inflate the bag with air) at 61-77 degrees Fahrenheit for 4-12 weeks. Each scale should sprout bulblets, which you can treat like stem bulblets, except leave them attached to their scale (as long as it is firm) and don’t bury them so deeply while the bulblets are small: 1/4 of sand over the scale bulblets is enough.