Why you (probably) shouldn’t be starting seeds yet

As a beginning gardener I learned that to give plants like tomatoes and peppers more time to grow and produce the largest possible crop, it was best to start the seeds early indoors.

gazaniaseedlingsAs soon as I learned that, I wondered: Well, if starting my tomatoes 6-8 weeks before transplanting them outside is good, surely 10 weeks would be better, right? Or 12? Or 16?

Turns out, earlier isn’t always better, and here are some of the reasons why.

First, you probably don’t have enough light. If, like most home gardeners, you are starting seeds under florescent bulbs, it is difficult to give sun lovers like tomatoes and peppers enough light. Light intensity drops off rapidly as you move away from the bulbs, so you know to keep the bulbs right above your seedlings. This works great when the plants are small, but as they grow it becomes very difficult to give both the tops and the bottoms of the seedlings enough light. The result is dying lower leaves and spindly, unhealthy growth.

rootboundSecondly, you are almost certainly going to get some crappy root systems. If you’ve followed this blog for a while, you’ve no doubt read Bert and Linda talking about all the potential problems with the root systems of container grown trees and shrubs. Well, most of the same problems develop with other plants grown in small containers. The roots start circling and they are slow to grow out of the rich soil of the container and into the native soil around them once transplanted into the garden. The longer your transplants grow indoors, the more likely they are to develop problematic root systems. Keeping transplanting them up to larger and larger containers can help mitigate the problem, but that quickly takes up far more space than most home gardeners have for there seedlings.

How big and impact that circling root system will have on the health of the plant varies by species. My personal experience growing zinnias, for example, is that they handle circling, pot-bound roots so poorly that plants from seeds sown directly in the garden quickly over-take and out-perform plants started weeks earlier indoors.

So follow the recommendations for the timing of seed starting. It really does work better. You should be able to get advice on when to start seeds from the catalogs you are shopping, extension offices, or you can use Margaret Roach’s excellent seed sowing calculator.

If you DO decide that earlier is better, that you can provide the light and generous pot sizes to avoid problems, there’s no harm in giving it a shot. But if you do, try starting a second batch at the later, recommended, time and growing the two side-by-side in the garden so you can really compare and see which perform best in the actual conditions of your garden, and if all that extra time and space under your lights or in your greenhouse was really worth it.

Joseph Tychonievich

Why some plants are “fooled” by a warm December and some aren’t

Here in Michigan – and, it seems, most of the Eastern US – we’ve been having unseasonably warm weather and there are odd things afoot in the garden. Some plants that would normally be dormant coming back into growth. But perhaps odder is that while some plants have been “fooled” by the unseasonable heat, others are still resolutely dormant and not pushing any growth at all despite the warmth. Why is that?

A wild rose with buds still tightly dormant despite unseasonable warmth
A wild rose with buds still tightly dormant despite unseasonable warmth
A 'Knock Out' rose pushing growth during a warm spell.
A ‘Knock Out’ rose pushing growth during a warm spell.

There are a lot of factors that determine when a plant is dormant and when in active growth, a key one in this context is whether they have a vernalization requirement or not. In simple terms, some plants, once they go dormant for the winter, will refuse to come back into growth until they’ve experienced a period of cold temperatures. Once they’ve been through that cold, the plant is termed to be vernalized and will then burst into vigorous growth as soon as the weather warms up again.

You’ve probably run up against a vernalization requirement in terms of bulbs like tulips. That requirement is why you need to give tulip bulbs a cold treatment in order to force them to bloom indoors, and why southern gardeners without sufficient natural winter cold have to pre-chill their tulips in order for them to bloom. The adaptive advantage of this is obvious in a year like this, as it prevents plants from jumping the gun in a mild December and getting damaged by the real cold when it arrives.

So why do are some plants lack this adaptation and come into growth in a freak warm spell? Some are adapted to life warmer climates and sometimes it is the work of humans. Modern hybrid roses, for example, have had their vernalization requirement bred out of them. The downside is that this makes them more susceptible for winter damage sometimes, but the plus side is that it is part of what causes them to bloom all summer long rather than just once in the spring the way most of their wild ancestors do.

Another good reason to mulch

Posted by Bert Cregg

Researchers often get accused of concluding the obvious.  At some point we’ve all scoffed at headlines like, “Study finds cell phones and driving don’t mix” or “Researchers discover high heels make your feet hurt.”* But even when a study demonstrates something we already know, sometimes there is still value in being able to put hard numbers on the scope of the problem – and hopefully spur some action.

A case in point is a recent study by Justin Morgenroth, Bernardo Santos, and Brad Cadwallader at the New Zealand School of Forestry, “Conflicts between landscape trees and lawn maintenance equipment – The first look at an urban epidemic” Urban Forestry and Urban Greening 14:1054-1058.  Morgenroth and his colleagues surveyed over 1,000 trees in public greenspaces (parks, cemeteries, campuses) in and around Christchurch, New Zealand (pop. 375,000) to assess the amount of damage to trees by lawn equipment.  Their conclusion: Lawn equipment is hell on trees.  This conclusion, of course, surprises absolutely no one that has ever looked at trees near turf in a public place on this planet.

lawn mower blight 2

 

Morgenroth et al. claim their survey is the first systematic look at this issue and their data are staggering.  Nearly two-thirds (63%) of the trees they surveyed had at least one wound.  The proportion of trees with wounds was fairly constant regardless of type of planting (i.e., park, campus, cemetery, roadside verge), though trees in parks and campuses tended to have more wounds per tree than trees in nature reserves or roadside verges.

Not all the news was bad, however.  Morgenroth et al. found that grass cut-outs or mulching around trees significantly reduced the number of wounds per tree.

So, not a conclusion that should take anyone by surprise, but some sobering data to put some scale on the size of the problem.

 

*actual conclusions from real studies

Just post some pretty pictures or something

Posted by Bert Cregg

A little over six years ago Jeff Gilman called me out of the blue and asked me to be part of a new blog about the science of horticulture that he was embarking on along with Linda Chalker-Scott.  I was reluctant – I didn’t know much about social media at the time and was plenty busy already.  Jeff explained that he was recruiting others and how we would rotate posts. I asked Jeff, “What if I don’t have anything to write about?”   Jeff replied, “Just post some pretty pictures or something.”  So with that long ago conversation as backdrop, here are a few photos from this week’s trip to Hidden Lake Gardens near Tipton, Michigan.

Sugar maple fall color
Sugar maple fall color
Entrance to the Harper Collection of Dwarf and Unusual Conifers
Entrance to the Harper Collection of Dwarf and Unusual Conifers

Taxodium distichum "Pendens' cones

Taxodium distichum “Pendens’ cones

Pinus contorta "Chief joseph'. With apologies to Joseph Tychonievich...
Pinus contorta “Chief joseph’. With apologies to Joseph Tychonievich…

Sassafras albidum fall color

Sassafras albidum fall color

The long and winding road...
The long and winding road…
Sciadopitys verticillata 'Joe Kozy'
Sciadopitys verticillata ‘Joe Kozy’
Abies koreana 'Icebreaker'
Abies koreana ‘Icebreaker’
Taxodium distichum 'Pendens'
Taxodium distichum ‘Pendens’

 

Native vs Exotic: Not as simple as it seems

Lots of discussion recently over on the Facebook side regarding the recent publication in Ecological Letters by Karin Burghardt and Douglas Tallamy, “Not all non-natives are equally unequal: reductions in herbivore β-diversity depend on phylogenetic similarity to native plant community.” http://onlinelibrary.wiley.com/doi/10.1111/ele.12492/full
While there are certainly some things to nitpick in the paper (see Linda’s comments on the Facebook discussion), I think this paper may go a long ways re-shape, and possibly even begin to end, the debate over native versus exotic.

How was the study conducted. In 2006 Tallamy’s group established a series of test landscape plantings. Each planting fell into one of four groups: non-native congeners (species that are not native but have native relatives in the same genus); non-native non-congeners (plants from non-native genera), native congeners and native non-congeners. In 2008, when the trees were about 6’ (1.8 m) tall, they conducted a census to identify and quantify the adult and immature insect herbivores they collected. They analyzed the data to determine the amount of insect herbivore diversity within each planting type. Specifically they looked at what ecologists refer to as beta-diversity, the amount of species diversity among sites. If you’re interested and want to learn more check out https://methodsblog.wordpress.com/2015/05/27/beta_diversity/

So, what did they find? Like every good study on host-insect interactions; the answer is, “It depends.” (BTW, if you’re following along at home the key figure in the paper is Fig. 3). When Burghardt and Tallamy looked at the differences in diversity between adult herbivores on native and non-native congeners, they found no difference. When they looked at differences in diversity between immature herbivores on native and non-native congeners, they found no difference. When they looked at differences in diversity between adult herbivores on native and non-native non-congeners, they found no difference. When they looked at immature herbivores on native and non-native non-congeners, they found a small but statistically significant difference, with higher total diversity for native non-congener.

As an aside, it is also instructive to look the version of Figure 3 presented in the article’s supplemental materials, which has been re-scaled to include zero. Including zero on the scale helps to give a better perspective on the actual variation among means. It’s a little like the “Truth in lending statement” that comes at the end of your credit card bill.

tallmay re-scaled

So, a possible alternative title for the paper could be, “Do native or non-native plants increase herbivore diversity? Most of the time it doesn’t matter.” That said, I think this paper makes a number of contributions and will start to shift native versus non-native debate, and perhaps even signal the beginning of the end. First of all it demonstrates that that non-native species of native genera contribute equally to herbivore diversity. However, I think some of the most insightful information in the paper is buried between the lines and in the supplemental information attached to the online version of the paper. The authors briefly mention that they also looked at guilds (i.e., chewing insects, sap feeding insect, xylem feeders, etc.). Once again the answer of whether natives contribute more to species diversity is, “It depends.” For xylem feeders, for example, diversity was the same for congeners and non-congeners.

To me, this is the level of resolution we need to work to gain a true handle on the situation. I’m not an entomologist and I’ve never played one on TV but I’ve been around these questions long enough to know that different types of insects are attracted to or repelled by different plants by different mechanisms. In one case it’s an attraction pheromone, in another it’s a defense chemical, sometimes it’s leaf toughness or a tree is able to produce enough resin to drown boring insects. An old axiom states that ecosystems are not more complicate than we think; ecosystems are more complicated than we can think. As this paper demonstrates, to think that all the complex interactions between plants and insects can be boiled down to something as simple as native or exotic is hopelessly naïve.

Pretty in Pink

It’s October. Fall is such an underrated time in the garden, and much pink can be found. In fact, flashes of pink are everywhere!! Got my ma’ams grammed last week; thanks for the reminder, NFL.

Muhlenbergia ‘Pink Flamingo’.
Aye yi yi. Alleged hybrid between M. capillaris and M. lindheimeri. Five feet tall and as wide, huge plumes of pink. Looks like nothing important the rest of the year, then, blammo!!! Sorry, folks north of Zone 6. Actually, it only works here  (Z. 6a) because of outstanding drainage; it’s planted in a pile of gravel. Mine has lived through two winters with -20 F days.  Place where the sun will rise or set behind it for maximum effect. Bunny the Whippet not included.

muhleypinkflamingo

Salvia involucrata – Rosebud Salvia
Big ol’ gal that will not favor you with blossoms until September. Absolutely not hardy here, or anywhere north of Zone 8.  Take cuttings, ’cause baby she’s worth it. The furry, hot pink flowers will thrill any hummingbirds left zipping around (I read ours the riot act this weekend, they have GOT to hit the road soon). Note there is some hullabaloo as to S. puberula vs. S. involucrata vs. some hybrid amongst the two.  Will report back.

salviapink

Chrysanthemum x whatever ‘Venus’ .
Am so tired of the taxonomic uncertainty. ChrysanthemumDendranthemum…  Whatever you call her, ‘Venus’ is a wonderful “real” garden mum (not those heinous meatball things) that brings the pink blooms in September, then fades to palest of pink, but not before every bee in the neighborhood visits.  Fairly compact (2-3’) and pretty darn hardy (Zone 5). Tuck Venus amongst things you know will be done before fall – bee balm, phlox, etc. to keep the show going!

chrysvenus

So there you have it, some pink for our October gardens.  In loving memory of my sister Carlene.

Mitchella repens … Partridge Berry … an Evergreen Native Groundcover for Shade

NaturalSetting1

Partridge Berry in its Natural Setting

One of the questions that came up regularly when I was working the hotline at the local county Extension office, is a recommendation for an evergreen ground cover for shady spots.  I had the same issue when I created my own shade garden … something that would have year round interest, but complement my desire to emphasize native species, although that was only one consideration.

The solution was literally right next to me, as a walk in my woods revealed with the lovely plant Partridge Berry, or Mitchella repens.

Not only is Partridge Berry (Mitchella repens ) beautiful, evergreen, shade-loving, and native to Eastern North America, but there’s also a fascinating aspect about its flowers and fruit, from a botanical, and evolutionary point of view.

According to the U.S. Forest Service Celebrating Wildflowers website, the “… genus name Mitchella was given to this plant by Linnaeus for his friend John Mitchell, a physician who developed a method of treating yellow fever. The species name repens refers to its trailing or creeping habit.”

Berry1

Here’s the part I found fascinating: The plant is dimorphous, meaning “occurring in two forms”:

In late spring, two beautiful white flowers (with one calyx) each open their four petals to entice insects to collect their nectar. Each blossom has one pistil and four stamens. The pistil in one is short and the stamens are long. In the other it is just the opposite. … Because of this no flower can fertilize itself–all flowers must be cross-pollinated by insects, and both flowers must be pollinated to get a single healthy berry. A berry will stay on the vine until after the blooms appear in the spring unless a hungry bird finds it nestled among the fallen winter leaves.

How cool is that?  The twin flowers produce, together, only one berry.

Berry2

Here’s a closeup, where you can see residual evidence of the fusion.  The berry is edible, and persists through the winter, assuming it is not consumed by “ruffed grouse, northern bobwhite, sharp-tailed grouse, and prairie chicken.

The fruit is also “frequently eaten by raccoons and red fox” and it has been reported that “partridgeberry made up 2.9 to 3.4 percent (dry weight) of the summer and fall diets of white-tailed deer.”

June2014Bloom1

Here’s a picture of the two flowers in bloom.

It’s easiest to spot the plant in its natural setting while hiking in late Fall, or early Winter before snowfall, or early Spring after snowmelt.

Back to the Forest Service article:

Some gardeners consider Partridge Berry a must for winter gardens. During the cold days of late winter Partridge Berry is a treat to the eyes with its deep, dark-green leaves and occasional scarlet berries. In a garden setting this evergreen prefers shade, accepting the morning sun. Partridge Berry is extremely difficult to propagate from seed.

The best way to introduce this native into your garden is through 1 year old cuttings or by division. In the garden situation they will form a thick, substantial ground cover. Once established they are relatively trouble free with the only required maintenance of keeping garden debris from covering the mats.

As always, do not wild collect plants from public lands and only from private lands when the landowner grants permission. Partridge Berry is a commonly available plant from native plant nurseries especially those who specialize in woodland plants.

I love the symmetrical variegation in the evergreen leaves, a bright, light yellow line bisecting each leaf, and the delicate, less visible veins.

It’s a great alternative to Vinca, an introduced species from Europe that appears on invasive species lists in our area.

A Google search will reveal many potential on-line sources for buying Partridge Berry plants, or check with a local nursery, or independent gardening center in the native plant section.