Wednesday, March 25, 2015

Enjoy It While It Lasts - Winter Jasmine, Hellebores, Daffodils, 'Georgia Blue' Speedwell, Boxwood Flowers and More!

After a harsh winter (especially last month - 8th coldest February on record in Tennessee) we have been basking in above-average temperatures for the past couple of weeks.

Yesterday's high temperature was 77 (Fahrenheit). The previous day was 73. Last week, we hit 80.

As a result, leaves, buds and flowers have been bursting out all over, making for a lot of pretty pictures (see below).

Unfortunately, temperatures are supposed to take a nose dive later this week. We're expecting lows in the 20s (perhaps as low as 23) on Friday night and Saturday night.

Usually, I am what you'd call a Darwinian gardener - I let plans thrive or die with minimal intervention. (Well, I water them for a season to get them established, but I don't spray or coddle after that.) But in this case, I'm tempted to try throwing a sheet over the crabapple tree. It's loaded with buds and I'm worried that many of them will be killed in the cold snap.

For now, enjoy these signs of Spring!

'Honey Bee Blue' Agastache (I believe A. rugosa). Purchased three from a local nursery last year, they all seem to be coming back nicely.

I'm pretty sure this is Agastache foeniculum 'Golden Jubilee' (anise hyssop), but the leaves should be emerging a chartreuse color. So perhaps the original plant has died and the seedlings have reverted to the species A. foeniculum? (Prairie Nursery does call the species a biennial.)  I'll post an update later in the year as to the foliage color as these seedlings mature.

Shoots and flower buds on Ajuga genevensis (blue bugle, Geneva bugleweed)

Sedum telephium (I believe the 'Autumn Joy' cultivar)

I'll admit it, generally I think boxwoods (Buxus) are boring and overplanted. Yet, the thing I like most about boxwoods is probably what other people overlook - not their bland evergreen foliage, but their sweetly-scented spiky flowers that attract pollinators such as bees and (as you can see here) other insects including flies. Flies don't get much respect, but I'm sure they have a bigger role to play in the world than landing on our picnic lunches.

And here's a bee (honeybee?) buzzing in the boxwood.

Clematis 'Crystal Fountain' -- got to do some judicious pruning here...

Aquilegia (columbine) self sows with abandon here. I love it and encourage it. Originally I planted a few different columbine species including the European A vulgaris and a hybrid called 'Winky', but I've decided to focus on adding and encouraging reseeding by the native species A. canadensis (wild columbine)

Purple coneflowers (Echinacea purpurea) are coming up throughout the garden, both as returning perennials and new seedlings. Again, love and encourage the reseeding. I'm also happy that the new seedlings are easy to spot and identify, unlike some species where you have to wonder for a while whether you're growing a desirable plant or nurturing weeds.

Look closely at the base of these stems and you could spot new growth emerging on Baptisia australis (blue false indigo). Although B. australis reportedly prefers well-drained soil and full sun, it seems to have done pretty well for a couple of years now in our heavy clay soil with a bit of shade from a neighboring crape myrtle tree. Note that the new growth can look a little bit like asparagus, but there is evidence that Baptisia is poisonous (for people) and should not be eaten! So to avoid a potentially dangerous misidentification, don't plant this anywhere near your asparagus patch!

Beautiful foliage and buds on the 'Sugar Tyme' crabapple. This is the one where I don't know whether I should try to provide some protection from the upcoming cold snap or stay true to my Darwinian ethos.

First cheerful blue flowers are appearing on 'Georgia Blue' speedwell (Veronica peduncularis)


Most of the year I'm neutral-to-negative on daylilies (overplanted, high-maintenance, don't seem to have much wildlife value), but I always appreciate the lush, fresh new foliage in March that leaps out of the ground when many other perennials are still snoozing.

Dianthus gratianopolitanus 'Firewitch' (cheddar pink) - I was thinking of planting more cheddar pinks as a groundcover, but I'm a bit concerned that this one could be dying off in the center after a few years, which would not speak well for its potential as a long-term groundcover. I think I'll wait to see how/whether it recovers over the next few weeks...

Geranium sanguineum (bloody cranesbill) - planted three tiny specimens of the 'Vision Violet' cultivar last year. They struggled a bit as they had to compete with a rampant patch of cherry tomatoes, but they all seem to have returned bigger and stronger than last year, so that's a good sign.

Added a couple of hellebores to the garden last month. Of course, I planted them just before our temperatures crashed below average and stayed there for weeks with temperatures dipping into the single digits multiple times. Since these had been growing in an unheated greenhouse and hadn't had a chance to harden off, I assumed they would be goners. I covered them cardboard boxes (weighted down by bricks) that subsequently got soaked by rain and collapsed by ice. When I gathered the courage to remove the boxes after a few weeks, the hellebores looked fit as a fiddle. These are some tough plants!

Alchemilla mollis (lady's mantle)

Stachys byzantina 'Helene von Stein' (lamb's ear)


Philadelphus x virginalis 'Natchez' (mock orange) - Bought this from a sale section in autumn 2013 and got a great bloom last May. Then the plant just say there all last year, not growing an inch. I worried as to whether it had exhausted itself with the bloom and was on the road to ruin. Then late in the season, it sent up a sucker about six inches with fresh new leaves. Was that a good sign or did it mean all the old growth had died off? Well, so far, things look good. I'm seeing all the old growth (and the new sucker) leafing out. I'll remain optimistic on the mock orange.

I don't know much about mosses, but I think they're fantastic from both a visual and tactile standpoint, so I try to encourage them in the garden. I don't know how to identify this moss, but it seems to be entering its reproductive stage where sporophytes will release spores that will hopefully help the moss spread around the garden!

Symphyotrichum oblongifolium 'October Skies' emerging from under a winter blanket of leaves. I'm pleased to see that all three clumps of October Skies aromatic aster seem to have expanded nicely.

Phlox paniculata (garden phlox) 'David' - As with the daylilies, I think the sight of the fresh green foliage emerging in early spring may be my favorite think about garden phlox. The foliage always seems to get pretty tattered (and sometimes mildewed) later in the season. Still, it's a tough plant that has come back reliably year after year, so I should probably learn to appreciate it more. (I think there are some little Agastache seedlings growing alongside it this year.)

Viburnum 'Pragense' (Prague viburnum). I had five of them planted last year. This is the most impressive one of the bunch and I'm still not impressed.

Here are two of the less impressive Prague viburnums (Viburnum 'Pragense')

I'm pretty excited to see that this Salvia greggii (autumn sage) survived the winter. It's only marginally hardy in our zone and supposedly dislikes poorly drained soil (which is a big problem with our heavy clay). Still, it's one tough cookie and I'm pleased to see that it's back for another round. The other autumn sage I planted last spring seems to have died back closer to the ground, but I still see some new leaves near the base of that plant.

Native to the Mediterranean, Teucrium chamaedrys (wall germander) supposedly needs (prefers?) well-drained soil, but it seemed to cope pretty well in lightly amended heavy clay. All three clumps survived the winter and stayed partially evergreen. I cut off some of the damaged foliage to reveal this fresh new growth. The clumps seem to be expanding at a measured, moderate pace.

Myrica cerifera (southern waxmyrtle) not looking good. This is another marginally hardy plant in our zone. It's mainly native to sandy soils in the Coastal Plain of the Deep South. Perhaps I should have planted it in the spring to give it a chance to get established before it had to face near-zero winter temperatures and ice storms? I may have been doing a bit of excessive zone pushing with this one...(To add insult to injury, I walked by yesterday - after this photo was taken - and saw that deer had chomped off most of the branches. They didn't eat it, they just decapitated the plant, said 'Blech!' and moved on.)

Jasminum nudiflorum (winter jasmine). I'd read that winter jasmine might flower as early as December or January, and perhaps it would if we'd had a couple weeks of warm weather, but with temperatures at or below normal, it started flowering around the same time as the forsythia in mid-March. Bloom was sparse this year, with some of the buds frozen before they had a chance to open. The flowers are cheerful and I like the green stems, but the plant has a reputation for being aggressive in the garden. I'm not terribly enthusiastic after the first winter, but I'll take a wait and see approach and hope I'm bowled over next year (in a good way).

Friday, March 13, 2015

What a Creep!

Creeping raspberry not looking its best. Unfortunately, I've found this mass of dead stems to be a common sight in back-to-back Tennessee winters. Would the plant look prettier in a warmer climate? No doubt. But it would also probably expand faster, and that's a somewhat scary thought for a non-native species with few obvious wildlife benefits. I'd be especially wary of planting this next to any wild areas where it could expand and try to outcompete native vegetation. Oh and notice how despite its rampant growth, it has failed to block out all the love-in-a-mist seedlings poking through in the foreground.

I'm not talking about the iconic Radiohead song from the 1990s, but rather the creeping raspberry (Rubus rolfei, a.k.a. R. calycinoides or R. pentalobus).

I've reported on this plant twice before:

- In October 2013, I was over the moon with anticipation that I'd found the perfect groundcover. I waxed rhapsodic about its merits - the scalloped crinkly leaves, its supposed evergreen foliage, its rapid growth rate and its reported wildlife value (flowers for pollinators, berries for birds and mammals - including people).

- By April 2014, I was singing a different tune after the creeping raspberry died back to the ground in the winter of 2013-14 and took a long time to emerge in the spring. My dreams of a trouble-free evergreen groundcover disintegrated as I clipped back tough raspberry stems with dried dead leaves.

Now it's March 2015 and I've permanently broken up with creeping raspberry. After another colder-than-average winter (8th coldest February on record in Tennessee), creeping raspberry once again had lots of unsightly, dead stems.

After three growing season in the garden, the biggest plant had rooted all along its runners to establish a thick multi-layered patch that spilled out of a bed and onto a sidewalk. All the new plantlets grew so fast that they created maintenance work in the garden as I had to trim back the runners pretty frequently to prevent them from covering the sidewalk. (I'm pretty sure that left on its own, creeping raspberry would have crept right over the sidewalk and rooted into the grass on the other side.)

Creeping raspberry roots all along its nodes. These rooted sections send out their own runners, so the plant self-propagates and expands with ease. Too much ease for my comfort, especially when we're talking about a non-native plant with little obvious wildlife benefit and limited aesthetic appeal.

Those berries and flowers I'd hoped for to give the groundcover wildlife appeal (and provide a handful of fruit now and then for me)? Never saw them. (Well, I saw a single flower the first year I had the plant in the garden, but nothing ever bloomed after that. Perhaps creeping raspberry only blooms on old wood and thus can't flower or fruit in a climate where it keeps getting killed back to the ground?)

Creeping raspberry is a conundrum. Despite its wild and wandering ways, despite its multi-layered foliage, it still doesn't do that great a job of blocking weeds. In fact, I'd say it's least effective at blocking weeds than any of the other groundcovers I'm trialing in my garden (such as lamb's ear, perennial geraniums, creeping veronica, epimediums, ajuga or lady's mantle).

This is a Cambridge geranium (Geranium x cantabrigiense) called Biokovo. So far, I'd say it makes a much better groundcover than the creeping raspberry here in Tennessee. As you can see, it's stayed mostly evergreen through the winter with some nice reddish highlights in the foliage. Unlike the creeping raspberry that forms tough and wiry stems, I've never needed to cut back Biokovo. The last year's foliage slowly fades away and is superseded by fresh new foliage, plus Biokovo gives you weeks of white flowers with pink centers. The dense foliage does an excellent job of blocking weeds and the clump has expanded at a measured pace while staying dense in the center. 

So yesterday I decided it was time to give creeping raspberry the heave-ho. It did not go without a fight. That main clump which had only been in the garden for around three years had set some serious roots. In some ways, it was like trying to dig out a small shrub. To give you an idea, I had a much easier time digging out three (less-established) clumps of Amsonia hubrichtii (Arkansas blue star), no shrinking violet itself, than I did prying creeping raspberry out of the ground.

The trouble I had removing the plant convinced me that I'd made a very good decision to remove it when I did. Given another year or two, I fear this non-native groundcover would have insinuated itself throughout my planting bed, making it much harder to remove it without doing damage to some of the other perennials and shrubs nearby.

So what do I plan to put in its place? I have a couple of ideas. One possibility is Gaillardia x grandiflora (a hybrid between two North American species - G. aristata and G. pulchella - both of which are primarily native to the western United States, although G. pulchella's range does extend naturally into Southeastern coastal regions). Gaillardia x grandiflora has a reputation as being a short-lived perennial, especially on the sort of heavy clay soil that predominates on my property, but I have a few clumps that have fared very well on the other side of the driveway for a couple of years and I like the fact that it flowers profusely for many months during the growing season, attracting bumblebees and other pollinators. It's a very cheerful plant. Even the spent flower stems are attractive, so I leave them up through the winter and then cut the plant back to its basal foliage in early spring.

I may go with gaillardia as a replacement, but I do have a few other options I'm mulling over. Stay tuned!

Thursday, March 12, 2015

Fire and Ice

Well February was a bear -- eighth coldest February on record here in Tennessee, or so they tell me.

The last few days have been a breath of fresh air and I'll soon be posting photos of Spring busting out all over.

But for now, the most interesting garden photo I have on my camera card is from one of the ice storms we got a couple of weeks ago.

Sure ice storms are dangerous, damaging and inconvenient. They do, however, produce some beautiful impromptu ice sculptures...

Salvia greggii 'Flame' not looking so hot.

Monday, December 22, 2014

Slightly Famous -- Interviewed by Dave Ledoux on BackToMyGarden

A little while back, I had the honor of being interviewed by Dave Ledoux for his entertaining and educational BackToMyGarden podcast show.

In case you'd like to hear the dulcet tones of my mellifluous voice, here's a link to episode #61: Growing the Garden of Aaron.

Wednesday, December 17, 2014

Still Useful After All These Years -- Vintage Advice on Hedges from the 1960s!

Cat hedge
Wrap it up and put a bow on it.
Photo courtesy of Lance McCord

Sometimes I love the Internet.

How else could I stumble across a 1960s report from the University of Tennessee detailing the results of years of trials into hedging experiments with popular landscape plants.

Much of the report is still useful today, nearly 50 years from when it was first published.

I learned that Abelia x grandiflora (still very much in use today) and Spiraea thunbergii (fallen out of favor) showed no ill effects from a 7-week drought.

On the other hand, ornamental quince (Chaenomeles) was nearly completely defoliated by the drought, which is interesting since numerous sources list Chaenomeles as being drought tolerant.

(Of course, the report does not say - as far as I could tell - whether the Chaenomeles was permanently damaged or only temporarily set back by the drought. Some gardeners might be willing to accept a temporary defoliation is the plant is just trying to prevent water loss (transpiration) from its leaves, but if it will leaf out again once the drought passes or in the spring...)

Shark hedge
Something fishy going on with this hedge
Photo courtesy of Len Matthews

The study also details the effect of cold weather on the hedging plants, particularly due to the winter of 1962-63, which if my secondary research is accurate, reached an official low temperature of -5 degrees Fahrenheit in Knoxville (where the study took place).

The winter hardiness research showed that plants like Ilex vomitoria (Yaupon Holly) suffered hardly any damage, which is interesting since most sources only list Yaupon as being hardy to zone 7. (In other words, it should have suffered major damage below zero degrees Fahrenheit, but apparently it did not.)

On the other hand, the cold winter apparently killed Lagerstroemia indica (Crape Myrtle) to the ground, which was not surprising. What was surprising was that it also reportedly killed Pyracantha crenato-serrata (Firethorn) to the ground.

Now Pyracantha is not used much today around Middle Tennessee, probably due to those vicious thorns. To give you an idea of its relative popularity, I'd say more than 50% of the houses in my neighborhood have crape myrtles on their property (and yes, many of those did suffer major damage due to the -2 Fahrenheit temperatures we encountered last winter, particularly the crapes that had been pruned back), whereas I've seen a grand total of one property with a few Pyrcanthas (looking glorious laden with berries) by the front foundation.

But I don't think Pyrcacanthas fell out of favor due to lack of reputed cold hardiness. Most sources I've seen list Pyracanthas as being hardy to zone 6 -- so they should have fared better than the Yaupons. But they didn't. That kind of first-hand scientific reports of heat and cold tolerance is invaluable.

(I should note that most Pyracanthas sold today are P. coccinea, not the P. crenato-serrata species of days. past. Perhaps coccinea has greater cold tolerance? It's hard to find much information on crenato-serrata via Google these days.)

I believe in hedges - just like John Lennon did
I think John Lennon had a song about hedges...
Photo courtesy of NCM3

But what is also interesting about the 1960s guide is what it omits.

Guess how many mentions of bees?


How about butterflies?


Birds, moths, small mammals?


In fact, there are no mentions of pollinators or wildlife at all. It's as though they don't exist. The concept of planting a shrub / hedge for anything other than privacy or aesthetic reasons seems to have not even crossed the minds of the authors.

(There's also no mention of invasiveness, which could explain why the guide recommends Euonymus alatus, i.e., Burning Bush, which is still sold in many nurseries today despite its reputed invasive characteristics.)


Then again, the population of Tennessee in the 1960s was only a little more than half what it is today (~3.5 million Tennesseans in 1960 vs ~6.5 million Tennesseans in 2013).

My guess is that there was a LOT more open and wild space. People probably didn't feel the need to garden specifically to attract or support wildlife because it probably seemed as though most of the landscape already supported wildlife, ergo people could afford to devote their relatively small piece of the pie toward beauty or functionality (i.e., food, fuel, building materials for people).

The population of Tennessee, the United States and the planet continues to climb inexorably higher year after year. Even as human fertility rates drift lower, our demographic inertia carries us toward a planet more crowded with people with less space for all the other inhabitants.

Ergo, I believe it is incumbent upon all of us gardeners to do what we can to build and tend our gardens in a way that not only pleases our eyes and our palates, but also offers sustenance and habitat to the many creatures great and small who also call Earth home.

Thursday, December 11, 2014

Last of the 2014 Travel Reports - Fiery Foliage and Banana Trees in Delft!

Thanks for keeping me company as I've shared some of my favorite horticulture or eco-travel memories from Germany and the Netherlands over the past couple of months.

This is my final travel report for 2014 and it's a quickie.

Although I spent most of my time in the Netherlands in Amsterdam (plenty to see and do there!), I did take a quick day trip to the nearby cities of Delft and The Hague.

Both have their appeal. I think I'd like to head back to The Hague someday, if only to sit once more surrounded by Vermeers at the Maruitshuis museum!

As for Delft, we traveled there especially to visit the Royal Delft pottery factory (very nice and a great source of Made in the Netherlands souvenirs).

We then took a small detour (which turned into a longer detour due to my lack of navigational skills) to visit the Botanical Gardens at the Delft University of Technology.

Truth be told, the gardens were a bit of a letdown to me, although I didn't really have time to explore fully since we had to make our way to The Hague before the Maruitshuis closed, but I did find two noteworthy plants that I'd like to share with you all without further ado:

Banana trees in the Netherlands?! It sure looks like it.
Of course, these are in large planter boxes, so presumably they can be moved inside for the winter.
Botanical name is Ensete ventricosum, known as a Red Abyssinian Banana or Ethiopian Banana.
Kew says it serves as a staple food crop in Ethiopia.
This is actually the same plant that I saw growing in Kentucky this past August at Yew Dell!

There was no sign on this plant, but I'm fairly certain it's some sort of Fothergilla.
I couldn't say if it's F. major or F. gardenii, but I could say that the fiery multihued foliage is spectacular.

Thursday, December 4, 2014

Travel Report from Amsterdam - Hortus Botanicus Garden

One of the horticultural highlights of my three-week trip to Europe was visiting the Hortus Botanicus botanical garden in Amsterdam.

Though the garden is quite petite by U.S. botanical garden standards (only 3 acres), but it does manage to pack an impressive 4,000 species into that space. It also definitely has an edge over North American botanical gardens in terms of longevity since it was founded back in 1638, more than a century before the United States declared its independence from Great Britain.

Here are some of my favorite sights from the Hortus Botanicus in Amsterdam:

As soon as we stepped into the garden, my wife noticed this frog hopping across a gravel path. Always a good sign when the local garden ecosystem can support frogs!

New England Aster (Symphotricum novae-angliae), it's a pretty plant if you focus on the tippy-top and ignore the 5-6 feet of dead and dying foliage underneath. Also note that the garden had to corral the plants with a cord to keep them from flopping all over the place. In short, a vivid illustration of why there might be better ex-Asters for your garden. 
Honeybee hive hidden in a corner of the garden

This is Decaisnea fargesii, an Asian tree known colloquially (for obvious reasons) as Blue Bean, Blue Sausage Fruit or the unforgettable Dead Man's Fingers. Having only read about this in books, it was fun to see it in person for the first time! Not only does it make a eye-catching ornamental, but the fat long blue seedpods can be split open to reveal an edible and potentially sweet pulp (along with reportedly inedible seeds). I did not sample the fruit in Amsterdam. Unfortunately, Blue Sausage tree apparently cannot tolerate drought or hot summer climates, which I suppose explains why it's growing in cool Amsterdam and why I've never seen it in Tennessee.
Hortus Botanicus Amsterdam has a marvelous Butterfly Greenhouse. Here you can see butterflies emerging from their chrysalises. 

The butterflies are raised on site in a separate greenhouse that's normally off-limits to the public (although I was able to sneak a peak). These are some Very Hungry Caterpillars!
I had a chance to pet this fuzzy caterpillar and see the chrysalis that this species builds. The caterpillar felt soft as a teddy bear. (But don't assume that any fuzzy-looking caterpillar is safe to touch -- some of them can pack a hidden punch!)

I believe this is the same species of butterfly as in the photo directly above. Notice how the colors fade with age. 

Here are some amazing Glasswinged butterflies with transparent wings that appear to have just emerged recently from their chrysalises.

One of my favorites - the Owl Butterfly!

Another Owl Butterfly

Zebra Longwing butterfly, I believe

This was a rather interesting tree. First, as you can see, it's been grafted and the graft is quite obvious since the very bottom of the trunk looks dramatically different from the rest of the tree. I don't remember the identity of the rootstock, but the scion (the top part of the plant) is apparently a species called Manna Ash or Plume Ash (Fraxinus ornus). I'd never seen this kind of tree before and outside of its handsome ornamental characteristics, I was interested to read that the tree apparently produces a sugary sap (known as Manna) that can be used as a gentle laxative!

This is a robust clump of Kalimeris pinnatifida, also known as Double Japanese Aster. Highly recommended by Allan Armitage at University of Georgia. I hope to try this in my garden at some point. Clearly it seems to have a flopping problem, at least when grown in a somewhat shady spot. (Maybe it's more upright with more sunshine?) Regardless, the foliage certainly looks much better than that of the New England Aster.


This is Osmanthus heterophyllus, also known as False Holly for obvious reasons. I'd like to try some of this in my garden, but it's very hard (impossible?) to find locally except for the highly variegated "Goshiki" variety. Goshiki is nice and I may end up buying that by default, but I wish that some of the local nurseries started carrying one of the green cultivars.
Finally, I bring you a Plant Behind Bars!
Yep, it's a caged Wollemi Pine.
Don't worry - the plant is not dangerous to people!
Rather, it's people that might be dangerous to the plant, and since this is a very rare and endangered species -- once thought to be extinct -- the Hortus Botanicus is determined to protect it.
It was quite a neat experience to see this so-called living fossil, a link to a faraway era.