Skip to content
Elisabeth C. Miller Library

Archives: Plant Answer Line Q & A

Plant Answer Line questions and answers.

Propagating vernal witch hazel

Do you have any information on how to propagate vernal witch hazel?

To propagate vernal witch hazel (Hamamelis vernalis), Michael Dirr’s Reference Manual of Woody Plant Propagation (Varsity Press, 1987) says the following:

From seed:
70% germination after 3 months cold stratification,
75% after 3 warm months/3 cold,
81% after 4 warm months/3 cold,
85% after 5 warm/3 cold.
Fall planting improves success.

From cuttings:
Easy to root and keep alive.

Grafting is not used much as a propagation method.

The American Horticultural Society’s book, Plant Propagation (DK Publishing, 1999) says that softwood cuttings do not overwinter well. One should take early nodal stem-tip cuttings as soon as new growth in spring is 2 3/4 – 4 inches long. Provide bottom heat and rooting hormone to speed rooting in 6-8 weeks. Layering can also be done in spring. Grafting can be done in late summer.

The following is from the Royal Horticultural Society:

“To propagate by seed, harvest as soon as the fruits mature in late summer to early autumn and sow in a cold frame promptly before they have a chance to dry out. Fresh seeds may take up to 18 months to germinate. When the seedlings appear, prick them out and pot them up for overwintering in the greenhouse for their first year. They can be planted out late the following spring and will reach flowering size in about six years.
Witch hazel suckers freely and also can be propagated by layering in early spring or autumn. Layering works well, but the process will take a year.
Softwood cuttings can be rooted in the summer. Volunteer seedlings can also be potted up and transplanted.”

Transplanting Hydrangeas

I want to move my Hydrangea to another location. It is about 3 feet high, and doesn’t have enough room. What is the best time of year to transplant this Hydrangea?

The key to moving your Hydrangea successfully is to do it when the plant is dormant. According to the North Dakota State University Extension Service, it should have no leaves on it when you move it. If you missed the chance to do this in the late fall, you could still do it in early spring before it has new growth. It is a good idea to apply compost on and around the new planting site. There is a Hydrangea website that has a more detailed discussion of the Hydrangea’s transplanting needs.

On the sweet smell of katsura leaves

One of my favorite autumn things to do is shuffle through the leaves of every katsura tree I pass. What causes that enticing burnt sugar smell? Are there other trees that smell like this?

As the leaves of katsura trees (Cercidiphyllum japonicum) begin their process of decay, they are releasing molecules of maltol into the air and conjuring up scents reminiscent of toffee, cotton candy, or—as the German common name Kuchenbaum and the French arbre à caramel suggest–baking cake and caramel.

Maltol is also found in pine needles and lark barch, but it is most famously noticeable in katsura trees as they begin to turn color and the complex sugars in their leaves break down.

Salmon DNA in trees

Does salmon DNA end up in trees?

I saw a show about decomposing salmon being great for riparian ecosystems and that DNA from salmon could be found in the trees. Well, I shared this information with kids and a smart teacher fact- checked it with a scientist who said, no way! Nitrogen and carbon can be found, but not DNA.

It would certainly be cool if there were salmon DNA in trees, but is this true?

It seems obvious that decomposing salmon left by bears around forest trees would leave detectable traces of salmon DNA. Perhaps, along with the nutrients that are being added to the soil and taken up by the trees, there might be a detectable amount of salmon DNA in the trees, too. Certainly there is salmon DNA in salmon carcasses, the carcasses provide nutrients taken up by the tree, but does a test of the tree show traces of salmon DNA?

Let’s see what scientists in the field have to say. T.E. Reimchen is in charge of the lab at University of Victoria and is in charge of the Salmon Forest project there.

Here is a brief excerpt from their research:
“Conifer trees adjacent to salmon rivers on the west coast of North America incorporate marine-derived nitrogen from the carcasses of salmon carried into the forest by bears and other scavengers. We demonstrated (Reimchen et al. 2003) that small samples of wood (30 mg) extracted from cores of ancient trees contain detectable levels of 15N [nitrogen]. Comparisons among watersheds differing in number of salmon show that 15N levels in wood of trees are directly proportional to the present numbers of salmon entering the streams.”

When asked directly about the DNA question, Reimchen said, “I presume that the nitrogen that the tree is sequestering has come from the breakdown of the nucleic acids in the salmon. Have not heard about the incorporation of salmon DNA or RNA into the roots.”

Ray Hilborn, Professor of Aquatic and Fishery Sciences at the University of Washington, said, “I don’t know anything about the DNA — I doubt that very much. However what you do find in trees near salmon rivers is what are called ‘marine derived nutrients,’ that is, nitrogen isotopes that the salmon brought in their bodies back to freshwater.”

It certainly sounds catchy to say there’s salmon DNA in the trees, but it is probably just shorthand for a more complex concept.

On harvesting Asian persimmons

When should Asian persimmons be harvested? Do they need to be fully colored and soft? I’d like to pick them before the crows and raccoons get them this year!

The answer to your question depends on whether you are growing an astringent or non-astringent variety of Asian persimmon. For example, Hachiya and Saijo are astringent, while Fuyu, Izu, and Jiro are non-astringent.

Asian persimmon (Diospyros kaki) can be picked when completely colored but still firm, as this link from University of California Master Gardeners of Napa County describes:
“When harvesting persimmons, allow the fruit to remain on the tree until it develops good color. Use pruning shears to cut the stem, leaving a short stem and the green calyx attached to the fruit. If the fruit is snapped off rather than clipped, the fruit may bruise.

“Astringent types such as ‘Hachiya’ can be left on the tree until they become soft-ripe, or you can harvest them when they have reached full color but are still firm. In that case, let them soften at room temperature before eating.”

In your situation, I recommend not leaving the fruit on the tree to soften if you want to keep the critters from harvesting it!

The California Rare Fruit Growers website has a thorough guide to growing Asian persimmons.

Nagami kumquat hardiness

I live in Redmond, WA and I recently noticed that we have been classified as Zone 8A – 8B instead of 7B. Most sources I read state that year-round outdoor planting for Nagami kumquats is recommended only for Zone 8 and above. What is your take on this? I’ve had a Nagami since November, but it has acted differently from what sources I read indicated. I also have a Meyer Lemon that I bring indoors and it did fine over the winter, but the Nagami shed all its leaves within 2 months starting from January. The peculiar thing was that the leaves shed were all green and healthy, leading me to believe it had entered dormancy. It started to grow new leaves in April, but I’m still puzzled why it entered dormancy in indoor conditions even though the less cold-tolerant Meyer flourished.

Long story short, if the Nagami sheds its leaves every winter, will it ever have enough time to produce mature fruit even if it did survive outside?

If you have any particular kumquat or citrus experts you could recommend, that’d be great! Thanks!

According to a local nursery (Raintree), the Nagami kumquat is hardy to 18 degrees, and may produce fruit here. So if we have a cold snap, as we occasionally do, it may be hard on the tree if it’s growing outdoors–unless you can provide it with protection. A friend of mine has grown kumquats before, and they produced fruit, but I believe a long period of subfreezing temperature killed her tree one winter/early spring.

Growing Citrus by Martin Page (Timber Press, 2008) says that kumquats (Fortunella japonica or synonymously Citrus japonica) are prone to zinc deficiency which results in smaller leaves and shorter shoots. They are considered very hardy, but this may be “due to their long winter dormancy.” Nagami grown in a pot will reach about 4 feet, but outside, it can get to 13 feet tall. Fruit is harvested October to January.

It’s possible your Nagami kumquat dropped its leaves because it was entering dormancy, but there are other causes to consider as well. According to the source cited above, leaf drop in citrus trees can be caused by:

  • sudden environmental changes (temperature, humidity, etc.)–bringing a plant inside to overwinter is likely to expose it to dry air
  • underwatering (don’t overcompensate by watering a leafless plant because it has no way of transpiring the water without its leaves; prune it the next spring by reducing shoots by about a third of their length)
  • overwatering (make sure container drains well; soil that doesn’t drain well can lead to yellowing leaves and leaf drop)

You may want to speak to a local expert at the Western Cascade Fruit Society, or the Home Orchard Society.

Also the nurseries that specialize in fruit trees are good resources:
Raintree

Cloud Mountain Farm

Burnt Ridge

Storing bulbs in colder climates

Do you have to dig up shell flower bulbs in the fall in New Hampshire?

Just to be sure we are talking about the same plant, when you say shell flower are you referring to Tigridia pavonia? It’s also called peacock flower and tiger flower, just to make matters confusing!

A publication from the Brooklyn Botanic Garden, titled Summer-Blooming Bulbs (edited by Beth Hanson, 2001), says that Tigridia is hardy in zones 7-10 but in colder areas the corms can overwinter in the ground with heavy mulch or they can be lifted in fall “to ensure their survival.”

This information from University of Minnesota Extension (an area with winters that may be cold like yours) gives suggestions on how to store bulbs:

“Most tender materials should be dug after the foliage dries up or is killed by frost. […] Tigridia pavonia (peacock flower) corm [Storage temperature:] 35 – 40 degrees F. Dig 6 to 8 weeks after bloom or after frost. Cure and store like gladiolus.”

It sounds as if it is safest to dig up the corms and store them, but you could experiment and leave a few in the ground but heap mulch over that spot in the fall.

Rhododendrons with winter flowers

Aside from ‘Christmas Cheer,’ are there types of Rhododendrons that have winter flowers and flourish here? I am imagining planting a couple in an island beneath some hybrid elm trees, so they would be in part shade. I have plenty of irrigation, and there is a slight slope to the location.

Another variety which is early to bloom is ‘Nobleanum.’ American Rhododendron Society’s blog has a post by a Pacific Northwest author who lists several others:

  • ‘Bo Peep’
  • ‘Seta’
  • ‘Snow Lady’
  • ‘Cilpinense’
  • R. mucronulatum ‘Cornell Pink’
  • R. dauricum
  • R. moupinense
  • R. strigillosum

One can also search the American Rhododendron Society site for varieties of Rhododendron which meet various criteria, including bloom time.

Meerkerk Gardens on Whidbey Island lists rhododendrons by month of bloom.

The Rhododendron Species Botanical Garden might be another good resource. They mention that they have just a few species which flower early.

Pseudovivipary in plants

I have grown Festuca glauca for many years. While they have an annoying propensity to seed themselves everywhere, I have never seen Festuca send off many little plantlets, as one of mine is currently doing. Of all the Festuca that I grew, this one got the least amount of sun, and was near other taller plants, and it was also probably exposed to the most humidity.

Is this really a sign of the Apocalypse, or just another result of a crappy summer?

We had lots of theories put forth by library staff and professional gardeners, but according to plant ecophysiology professor Soo-Hyung Kim, your plant is demonstrating vivipary (or in the case of plants like Festuca, which are in the family Poaceae, pseudovivipary). I found information about vivipary in an article by Thomas Elmqvist and Paul Alan Cox, published in Oikos, vol. 77, no. 1, pp. 3-9, October 1996.:
“Vivipary in flowering plants is defined as the precocious and continuous growth of the offspring when still attached to the maternal parent. Two main types, true vivipary (involving sexually produced offspring) and pseudovivipary (asexual offspring), may be identified. Vivipary has been described from slightly less than a hundred different species of flowering plants, of which we classify approximately 50% as having true vivipary, with the remaining species being pseudoviviparous.”

There is additional information in Flora of North America, vol. 24, p.392:
“Under adverse conditions, many species [of Festuca] may proliferate vegetatively, where leafy bulbils or shoots form in place of some or all spikelets. Some populations of Festuca are largely (or completely) sterile, reproducing almost entirely through such bulbils, a process termed pseudovivipary. Pseudoviviparous plants may be common or even abundant in certain areas and habitats.”

Some scientists (cited in Elmqvist and Cox article) suggest that pseudovivipary is an evolutionary response to a short growing season (as in arctic, alpine, or arid areas). Perhaps your plant is in its own microhabitat!

Japanese maples that tolerate full sun

Is there a Japanese maple of any variety which will withstand full sun without leaf scorching or color alteration?

I consulted Japanese Maples, 4th edition, by J.D. Vertrees and Peter Gregory (Timber Press, 2009), which has a guide to uses and characteristics of different cultivars. Below is a list of the ones whose preferred light conditions are listed as “sun,” as opposed to “shade” or “any.” However, that probably doesn’t mean that they will withstand absolutely searing sun with a lot of reflected heat from pavement, etc. The authors say that green varieties and their cultivars take full sun very well, but may sunburn in late-summer heat. You can prevent this if the tree is planted where it will get afternoon shade, and if you are vigilant about watering. Avoid variegated forms, which will need semishade. Also, red-leaved cultivars require full sun if you are to obtain the best color from them.

  • Amagi shigure
  • Aoba jo
  • Aratama
  • Autumn Red
  • Beni hime
  • Beni yubi gohan
  • Bewley’s Red
  • Bloodgood
  • Boskoop Glory
  • Chirimen nishiki
  • Crimson Carol
  • Deshojo
  • Dissectum Nigrum
  • Dr. Tilt
  • Eddisbury
  • Emperor 1
  • Fireglow
  • Garnet
  • Glowing Embers
  • Hagoromo
  • Kiri nishiki
  • Kogane nishiki
  • Margaret Bee
  • Masu murasaki
  • Matsugae
  • Oshu shidare
  • Otome zakura
  • Pendulum Julian
  • Pink Filigree
  • Red Filigree Lace
  • Red Flash
  • Samidare
  • Sekka yatsubusa
  • Shaina
  • Shigure zome
  • Shikage ori nishiki
  • Shojo
  • Shojo shidare
  • Stella Rossa
  • Summer Gold
  • Sunset
  • Taki-no-gawa
  • Tennyo-no-hoshi
  • Trompenburg
  • Vandermoss Red
  • Villa Taranto
  • Waterfall
  • Watnong
  • Yezo nishiki