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Elisabeth C. Miller Library

Keyword: Pruning

Hydrangea pruning

It’s January, and my hydrangeas look bedraggled and terrible. When should I prune them?

 

The answer will depend on which species of hydrangea you are growing. According to the American Horticultural Society Pruning & Training edited by Christopher Brickell (DK Publishing, 1996), Hydrangea macrophylla (big leaf or mophead hydrangea) should be pruned after flowering in warm climates but in colder climates it is best to leave the old flower heads on the plant over the winter, and prune in spring. This rule also applies to Hydrangea serrata. If your hydrangea is blue-flowered, it is probably H. macrophylla. In her Guide to Pruning (Sasquatch Books, 2006), local pruning expert Cass Turnbull of Plant Amnesty says this plant should not need much pruning, but if you want to remove the faded blooms, you can do this in February by looking for four or five pairs of plump buds below the old flowers, and cutting just above the lowest or second lowest set of buds.

Hydrangea paniculata should be pruned in early spring, before active growth begins.

Hydrangea arborescens needs little pruning, and any pruning at all should be done in early spring.

Oakleaf hydrangea (Hydrangea quercifolia) also needs little pruning, but may be pruned in spring.

The U.S. National Arboretum offered a good introduction, no longer available on their website, but excerpted here:
“Established bigleaf, panicle, oakleaf and smooth hydrangea plants can often benefit from regular pruning. Removing about one-third of the oldest stems each year will result in a fuller, healthier plant. This type of pruning is easiest to do in winter, since the absence of leaves makes it easier to see and reach inside plants.
Gardeners may also want to prune to control height or to remove old flower heads. The best time for this type of pruning differs between species. Bigleaf and oakleaf hydrangea, which flower on previous year’s growth, should be pruned shortly after flowering is complete. Panicle and smooth hydrangea flower on current year’s growth and can be pruned anytime from late summer until early spring. If pruning these two species in the spring, try to prune before leaves appear. Plants of H. arborescens ‘Annabelle’ have been known to produce a second flush of flowers if pruned lightly after the first flowering.
Stems of bigleaf hydrangea that have been damaged by cold should be pruned as soon as it is determined that they are dead. Watch for new growth at the base of the plant. If your plant has basal shoots that are 6 to 8 inches in length, but the upper parts of the stems are still bare, then the bare stems need to be removed. For bigleaf hydrangea plants that are subject to frequent weather-related dieback, other than removing the dead stems, you probably won’t ever need to do any other pruning–Mother Nature has been doing the work for you.”

Kitsap County Master Gardener Peg Tillery, in an article formerly available on the WSU Extension Kitsap County web site, recommends waiting until March to prune hydrangeas: “In our climate we need to wait until early March to prune roses and summer blooming hydrangeas. This way the tender new growth won’t be harmed by frosts.”

The Royal Horticultural Society provides general pruning recommendations.

Here is an excerpt from a Seattle area gardener’s response to a question about hydrangea pruning on Garden Banter, a British gardening forum:

“Different species of hydrangeas have different criteria for pruning. Some
need very little pruning at all,other than to shape, as with H.
quercifolia and H. anomala petiolaris. H. arborescens does well with the
dramatic pruning you describe. Pruning of H. paniculata would depend on if
you were training it to be upright like a tree or as a broad shrub, and need
not be dramatic pruning, just barely enough to induce new growth on which
flowers occur, though in your zone a more dramatic pruning might be needed
because of winter damage. Most hydrangeas prefer late winter pruning, but
H. macrophylla is better done in late summer when flowers are getting
scruffy and new shoots are developing.”

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Pruning Hellebores

I am noticing that the flower bud shoots for my hellebores (Helleborus x hybridus), are starting to push up above the soil surface. There is still a substantial stand of foliage in good condition.

My question is about pruning. I know I’ll need to prune about half the leaves away (I understand that the cut should be made at the base) to give the flowers more visibility. Does it harm the plant to prune it during this cold snap? Does it harm the plant to cut ALL the old leaves off in December as the bud stalks begin to appear?

I would appreciate any guidance you can give me, such as when and how extensively to prune them.

 

According to Hellebores: a Comprehensive Guide by C. Colston Burrell and Judith Knott Tyler, “all the hybrids maintain their foliage (…) throughout all or part of the winter (…) In any case, as the flower buds begin to stir in the center of the rosettes, it’s best to remove all the foliage to make way for the flowers. Nothing spoils the garden display like a tangle of flowers wrestling with winter-burned leaves. The juice is caustic and sometimes causes a rash, so take care when removing the old leaves.”

In The Gardener’s Guide to Growing Hellebores, Graham Rice and Elizabeth Strangman advise a more time-intensive method:
“The best approach is to cut off some leaves during the autumn and early winter when the garden is put to bed, concentrating on removing dead leaves and any showing signs of blackening (…) By Christmas time they should be thinned out sufficiently to leave a good circle. However, as our winters become windier it may be wise to remove them entirely at this stage. (…)Thin the leaves further as the flower stems emerge, then just before they are in full flower remove all the old leaves. (…) To compensate for the removal of the last of the leaves the plants deserve a good mulch.” They go on to suggest compost or a mulch of leaves for this purpose. The cold snap is unlikely to harm even recently pruned hellebores, as they seem to thrive in the cold.

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Pruning clematis

There is a very large evergreen clematis starting to devour my detached garage. How far back can I cut this and when should I prune it back? It’s one of the first early spring bloomers with white flowers, possibly armandii? But I am uncertain…I need help since I don’t want to butcher it and lose it, but it needs a big haircut!

 

Clematis armandii does have the reputation for taking over the world. According to the American Horticultural Society’s Practical Guide on clematis (Clematis, by Charles Chesshire, 1999),
you can prune it AFTER is has finished flowering, which in Seattle, it normally does by the end of March. While this type of clematis can be pruned in late winter, it flowers on the previous year’s wood, so pruning at that time may remove buds and prevent flowering that spring.

Step 1 – remove any dead, dying, damaged, or deranged shoots.
Step 2 – they suggest that no real pruning is necessary but you can cut it back to control its growth. But you do NOT want to cut it all the way back into old dark, woody growth.
Prune directly above a pair of strong side shoots.
Step 3 – you will need to keep after it each year to avoid a build up of tangled growth.

Fine Gardening has an article by Lee Reich on pruning clematis here.

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Pruning hibiscus

I have a small hibiscus that I would like to train into a
tree with the twisted trunk and I have no idea how to go about that.
Please advise.

When you prune your hibiscus into a tree-like form with a single trunk,
it is called a standard. There are even braided topiary forms. To achieve
the twisted shape, you will probably need to create a support or frame.

The following general information on pruning comes from Tropical
Hibiscus:

“While the tropical hibiscus can be pruned any time, probably the ideal is
the earliest where the resulting tender new growth will be safe from cold
damage*. For shaping purposes, some growers will prune the longest third
of the branches and return in 4 to 6 weeks and prune the next longest
third. Only sharp, clean shears should be used. A clean cut should be
just above and angled down and away from an ‘eye’ or node. (A node is the
junction of a leaf and the stem. There is a small bud in this junction
that is activated after pruning.) Cutting above outward pointing “eyes”
will encourage growth in that direction. The new growth resulting from
pruning invigorates the plant and will provide a source for many new
blooms.”

The American Horticultural Society’s Pruning & Training (edited by Christopher Brickell and David Joyce, DK Publishing, 2011) describes the technique for creating a braided stem:
“Form a braided stem simply by braiding together three flexible young shoots. Select the strongest three on a multi-stemmed young plant, and remove the remainder. Single-stemmed plants can be cut back hard to produce multiple stems.”
The book also describes what is called a “barleysugar stem,” which may be more like the twist or spiral you envision: in this technique, “use a sturdy wooden pole with dowel pegs inserted in a spiral along its length. Train one or two stems around the pole, holding them in place by looping them beneath the dowels. Remove the pegs and the pole in sections when stem growth has hardened.”

Here is a link to Brooklyn Botanic Garden’s article on espalier forms, Special Cases: Pruning for Particular Purposes.

The Miller Library has a good selection of books on pruning and training,
and specifically on topiary. You can search the library’s catalog by clicking this link.

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On wind-sail pruning

There’s a self-described tree service knocking on doors in my street, trying to get people to pay them to do “wind sail reduction” on their trees. My neighbor just agreed to have them prune 17 of her conifers. Bad idea, right? Can you point me toward resources so I can dissuade her from going ahead with this plan?

Yes. The Washington Department of Natural Resources published an article, “Trees Don’t Wind Sail, Do They?,” in their online newsletter, Ear to the Ground, 12/20/2011. Here is an excerpt:
“Some people claiming to be tree experts will tell you that ‘wind sailing’ is a great way to protect your trees from wind damage. You may have heard this fabricated notion of thinning limbs from trees in order to make them stable during wind storms. This improper pruning technique is promoted to supposedly make trees safer in the wind by allowing wind to pass through the canopy of a tree, thus reducing movement and strain on a tree. Not so!

“This may sound reasonable and may even seem to have some logic behind it. But beware–the truth is, there is no scientific study that shows thinning is wise or safe way to decrease resistance during a wind storm.

“Actually, many studies have shown that the outside limbs can divert some wind from the center of the tree and act as a buffering shield. Aggressive thinning, on the other hand, can make the remaining branches more vulnerable to failure; left isolated, these limbs must take on the elements alone. Pruning out a major portion of a tree’s canopy for the sake of staying upright during a wind storm harms most trees in the long run.”

The DNR has another, similar article from 12/6/2012 in their Tree Link News entitled ‘Windsail Reduction:’ A Northwest Controversy.’

You can also suggest that your neighbor speak to someone at Plant Amnesty, a local organization dedicated to teaching the community about proper pruning techniques (as well as informing them about ill-advised methods!).

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pruning hardy fuchsias

I have several hardy Fuchsias that are quite large, about 4 – 5 feet tall, that bloomed profusely this year. The leaves are gone now, but when should I prune them? How far back should I prune? Is there anything special I need to know about pruning Fuchsias?

 

Fuchsias are pretty tough shrubs, especially once established. You can prune just to tidy them up, but it is best to wait until the leaves begin to grow (between March and June).

Here are two links to more detailed information:

From Rainy Side Gardeners,
“Some years when we have an exceptionally cold winter, Fuchsias will die down to the ground. Before pruning in spring, wait until leaf buds swell, then prune out dead twigs, or prune down to the ground if winter knocked it completely back.”

Another site is the Hardy Fuchsia List from the Northwest Fuchsia Society.

pruning and propagating Dracaena

My indoor Dracaena is getting too tall. I’d like to prune it, and maybe use the cuttings to start new plants. How do I do this?

 

You should be able to do both tasks. The Complete Houseplant Survival Manual by Barbara Pleasant (Storey, 2005) says “when plants become too tall, cut off the cane at any height. New leaf clusters will grow from just below where the cane was cut. You can cut sections into 6-inch pieces and root them like stem cuttings.”

You might also find this discussion from University of British Columbia Botanical Garden’s online forum useful.

Here is more information, from University of Florida, which describes how pruning will result in two or more branches forming where the pruning cut was made: “Cut one or two of the stems to a point where new foliage is needed.”

pruning elderberries

I have two different elderberries that I would like to prune.

1. The first is a ‘Sutherland Gold’ (a cultivar of Sambucus racemosa) that is 5 years old, and I have never pruned it.

2. The second is a ‘Black Beauty’ (a cultivar of Sambucus nigra) that I just bought last year.

When should I prune? At what point on the stems? How far from the ground?

 

I consulted Peter McHoy’s Practical Guide to Pruning, (Abbeville Press, 1993), and he recommends cutting one stem in three in mid-spring on plants that have been established for three or more years. You would cut to just above the ground level, choosing to prune out the oldest and weakest shoots first. Continue with cutting out shoots that will open up the center of the plant or improve its shape. It may look sparse afterwards, but new shoots will grow and fill in the space.

If you are growing the plants mainly for their foliage, he suggests cutting all the shoots back to 1-2 inches from the framework of the old wood in mid-spring.

Below is some more detailed information from the website of the Ontario Ministry for Agriculture, Food and Rural Affairs, which assumes you are growing the plants for their fruit production.

Pruning:

“During the first two seasons plants should be encouraged to grow vigorously with little to no pruning required. After the second year, pruning should be done annually in early spring. All dead, broken and weak canes should be removed. Three-year-old canes should be removed as they produce less fruit and appear to be more prone to winter injury. Removal of older canes will encourage the growth of new, more fruitful canes.

“Mowing of all the canes in a mature planting may be a method of reducing labour costs while encouraging growth of new canes. The disadvantage of this system is that there is a loss of production in the season following mowing as there is limited production on the one-year-old canes.”

Clematis and hard pruning

We are tearing out an old wood fence and replacing it with a new cedar fence, 6 feet high. We have a mature Clematis montana rubens growing on the old fence, prolific in growth and bloom, that I would very much like to save. Can I save it? We will have to start taking the old fence down right away. The new one is being installed next week, so I cannot wait until fall, which would probably be a better time to cut it back. Where do I begin pruning? Where do I stop? Anything I can do to lessen the shock to the plant?

Clematis montana is in pruning group 1 (or A) which means they do not take well to hard pruning. However, if it is the only way to save your Clematis, it is worth a try.

This is what the British Clematis Society recommends:

Category 1 (or A): No pruning.

“This category includes: C. montana If you wish to prune these types because they have outgrown their space they should be pruned immediately after flowering. You may or may not lose your plant as a result of the pruning. You might want to reduce the plant size over two or three seasons rather than in one go.

How-to: Start at the bottom of the plant and work your way up the stem to the first pair of plump, healthy buds. Prune the stem above the buds and remove everything above the cut. Treat each stem in a similar way.”

Pruning is safer than transplanting:

“If a Clematis is to be replanted from an existing site, the late winter before bud break is the time to do this. However, it is only the large-flowered cultivars that generally can be replanted from an open ground position due to their large fleshy roots. The Clematis species and their cultivated forms have a very fibrous root system that usually breaks up when it is being dug up. The montana types are extremely difficult to replant once they have been established for more than two or three years.”
Source: The Gardener’s Guide to Growing Clematis, by R. Evison, 1998, p. 39).

on what causes plants to flop over

What causes my chrysanthemums to do the big flop? One even came out of the ground! We have had a lot of rain lately, and it seems like a lot of plants did the big floppy, from roses to sedum, and now the mums. Is it all weather-related?

Yes, certainly the weather contributes to the big flop. Certain perennials just can’t stand up to heavy mist and rain.

Some gardeners stake their flop-prone plants before they flop over, while others dig them up and grow things that don’t flop.

You can prune perennials to help prevent flop. Typically you cut a perennial back by 1/3 a few months before it flowers. This causes the plant to branch out, producing a bushier, shorter, less floppy plant. In The Well-Tended Perennial Garden (Tracy DiSabato-Aust, 1998), the author suggests that staking be done early: …after the first flush of growth but before full growth. The stems need to be sturdy, and flower buds should not be formed yet…[stake] without adulterating the normal habit of the plants. Follow the natural line of the stem. (p.63)