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

Crossing borders with houseplants

I live in Seattle, but am going to Canada for an extended stay. Can I bring my houseplants across the border?

Generally, Canada allows houseplants from the mainland United States, but you may be asked to provide proof of origin at the border. The Canadian government page on guidelines for visitors and seasonal residents spells out the details. Here is an excerpt:
“Houseplants are defined as plants commonly known and recognized as such, which are grown or intended to be grown indoors. Bonsai plants are not considered to be houseplants. If you are importing houseplants from the continental United States as part of your baggage or household effects, you do not need phytosanitary certificates or import permits. For all other plants from the United States, you may require a phytosanitary certificate from the U.S. Department of Agriculture and an import permit from the CFIA.”

Spacing and growing butternut squash and raspberry

We’ve bought some butternut squash starts, and from what I’ve read online,
they require a lot of space. This will be my first time growing them. We
have 4′ x 6′ x 1′ raised beds, and I’m wondering if one bed will be big enough to plant 1 butternut squash start. Also, I’ve read that they require staking?
Is this true? What should we do with the other 2 starts that we got if we don’t have room for them in our raised beds? Try planting them directly into
the ground? I’d hate to throw them out…

We also bought a raspberry plant, and I’ve read that they should have 14-18″
for their roots. Again, our raised beds are only 1 foot deep. Would we be
better off digging a hole in the ground?

There is conflicting information in different sources about the amount of space butternut squash needs. Most sources say (as Seattle Tilth’s Maritime Northwest Garden Guide does) the gardener should allow 18-24 inches between plants, which would mean you could plant all 6 starts in one 4′ by 6′ raised bed. Steve Solomon, however, says in Growing Vegetables West of the Cascades that winter squashes require much more space, so that you could only plant two in your 4′ by 6′ bed.

Staking winter squash can be done to save space. There is a pretty good description of how to do it in Mel Bartholomew’s book, Square Foot Gardening. Basically, the vines are planted 4 feet apart in a trench prepared with “large-mesh wire fencing” on 6-foot posts, and twined through the fencing as they grow. He says the stems are strong enough to support the heavy squashes. The technique is also mentioned in Vegetables, Herbs & Fruit: An Illustrated Encyclopedia by Matthew Biggs, Jekka McVicar, and Bob Flowerdew.

As for your raspberry, it will grow faster and better with deep, rich soil. However, raspberries have a tendency to spread by underground runners, so it is often a good idea to contain them in some way. Depending on what is under your raised beds (i.e., soil, sand, concrete) you may wish to plant them there despite the shallow depth, or dig/mound up within the raised bed to improve the soil depth, or plant the raspberry elsewhere.