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Friday, May 17, 2019

How to Restore the Spring Flora of Oak Woodlands

A healthy, natural woodland is rich and rare. It has diverse, now-uncommon spring wildflowers, grasses, and sedges in every square foot, as summarized in this blog's previous post.

The spring flora provides the growing season’s first inspirations to woods lovers. More importantly, like the summer and fall flora, it is a crucial part of the functioning ecosystem. It provides the context in which new plants germinate and makes life-or-death difference for some pollinators, like the (federal endangered) rusty patch bumblebee. (For more on summer and fall flora, see “Fabulous Disclaimers” – below.)

This photo shows the spring flora of a restored woodland, 
Vestal Grove, where nearly all species but the trees had to be restored, starting in 1983. 
The easiest-to-recognize species here include wood betony (with its perhaps 
more-woodland-associated reddish color), large-flowered trillium, rue anemone, toothwort, 
bellwort, wild leek, spring beauty, trout lily, golden Alexanders, and yellow pimpernel – 
all spring species. Also present are starry campion (recognizable at mid-upper left 
with its paired leaves and dark purple stems) along with the sedges, grasses, 
and many summer and fall-blooming species that will be easier to identify later. 

This post reports on some successful (and unsuccessful) experiments with restoration in typical oak woods on rich soil (not sandy) that are not too wet or dry. (For woods that are dry, wet, sandy, etc., some of the same principles may apply, but the species lists would be different.) Much additional information is in Endnotes. (For example, see Endnote 1.)

Step one, if needed: Remove invasives possibly including many trees to achieve an “open canopy.” Otherwise the woods will be too dark. Indeed, in some woods you may need to remove many oaks as well. (For more on open canopy issues, see Endnote 2.) (If you’re starting in spring, you’ll want to gather seeds as they ripen. While gathering seed, you may also be able to eliminate most of the small invasives in late spring and early summer – so the pests and the herbicide will be gone before you start planting spring seeds in early July. But we often spray bad infestations of buckthorn seedlings and re-sprouts over a whole summer before we start seeding.)

Prairie trillium. Eye-catching – when dense like this – but not nature at its best. In the highest quality areas, competition is such that plants rarely make massive clumps. We come to treasure a coral-reef-like complexity. For those “super-plant” photos, go to a garden or a degraded (possibly recovering) area. 

Step two: Make a seeds plan. What species do you need, and how will you get them? One way to make the list is to look at the highest quality remnant woods nearby – but in most areas no very high-quality woods survive. Another source of info is any botanic history of your area. Compare notes with biodiversity conservation experts, if you can. Then decide whether to buy or gather seed. If your aim is a woodland that is significant to biodiversity conservation, you may choose the challenge and adventure of finding seed in nearby areas. On the other hand, given the reality of climate change, you may want to mix in seeds from 25 or 50 miles to the south. 

At Somme Woods we gather all our own seed, more than 200 species each year. (Of course, that includes the summer and fall flora – a much longer list of now-rarer species than the spring flora, that is the subject of this report.) In 2018 we collected 27 species for the “Mesic Intermediate” mix – the one we broadcast the parts of the woods with fewest trees and the parts of the savanna with the most. We gathered 26 species for the “Mesic Woods” mix – for the darker (but not all that dark) areas.

Step three: Make a burn plan. It’s not practical (and perhaps not possible) to restore health to a large oak woods without regular fire. That’s assumed, but not covered in this post.

Step four: Gathering Seeds – the major method of species restoration.
Well over 99.9% of the plants restored to Somme preserves are by seed. Even many rare and conservative species do fine if we just broadcast their seeds. 

How to recognize when seeds are ripe

Some seeds turn brown or some other distinctive color when ripe and remain on the plant for a long time. Those are easy. Most spring seeds are not of that type. Many fall off or explode soon after ripening. They may still be green at that time. You need to learn the species one by one. See tables, below. There are also references that help, for example the clunky table referenced in Endnote 4. Does any reader have other good recommendations?

Restoring by seed vs. by plug

We prefer not to do too much plug planting. Seeds are a better choice for most species, because you get orders of magnitude more plants per unit effort. But planting plugs has two advantages. For new stewards, it’s rewarding, because they hold a living plant in their hands and see its rapid success, if all works out. Also, for some species, plugs work better. But if seed planting works, it’s preferable for efficiency and ecology – because every generation that is produced by seed represents an evolutionary, biodiversity-promoting, gene-recombining event. For conservation, you want all the genetic alleles contained in thousands of seeds rather than the fewer in plugs. 

One major exception is when a high-quality area is being destroyed. In that case, with permission, we dig up sods of species that are otherwise difficult to propagate and install them in degraded areas we are restoring. Many other (often unnoticed, at first) plant species will hitch-hike on those sods, to the restoration’s benefit. Equally importantly, there is the chance that important fungi, bacteria, soil fauna, and other quality species will be restored as well. 

We also resort to plugs in the case of species for which we can gather very little seed. We germinate such seeds in pots and pamper the young plants for a year or two, however long it takes for that species to be able to compete in the wild. When we do plant plugs, we try to do it when the plugs (and the other vegetation) are dormant. 

By the way, if you want our advice on ethics, don’t ever dig up plants from the wild (unless on your private property, or with the owner’s authorization). It’s a short, slippery slope from a little plant poaching to evil, destruction, and damnation. 

Restored diversity: Here four species are blooming: wood anemone, cut-leaved toothwort, yellow wood violet, and common blue violet. But there's so much more.
Can you recognize plants by their foliage? If so, find these: Pennsylvania sedge, shooting star, wild geranium, grove sandwort, and white baneberry?
These nine are all spring species. Summer and fall species will emerge later.


The Easy Species

For these, all you need to do is gather the seed and broadcast it in the right place. We broadcast most early-ripening seed soon after we’ve gathered it. But the seed of some spring-blooming species will not ripen until fall. These include baneberry, green dragon, jack-in-the-pulpit, and broad-leaved puccoon.

The table below shows species that have been restored easily and in great numbers at Somme Woods. The “C” numbers refer to the natural quality of the species, higher numbers indicating higher quality or conservatism. Nature (and good restoration) includes species at all levels of conservatism. For “W” (wetness), lower numbers indicate species of wetter habitats, oddly. For more detail on C and W, see Endnote 3.

Common Name
Scientific Name
C
W
 When and How to Gather
wild onion
Allium canadense
2
3
 May produce black seeds, but most   people gather the green “aerial bulbs” that form.
wild leek
Allium tricoccum
7
3
 When they turn black and hard
wild columbine
Aquilegia canadensis
6
1
 When seed packet turns brown and the seeds black
green dragon
Arisaema dracontium
7
-3
 In the fall when bright red
jack-in-the-pulpit
Arisaema triphyllum
4
-2
 In the fall when bright red
wild hyacinth
Camassia scilloides
6
-1
 When seed packet turns brown and the seeds black
short-headed bracted sedge
Carex cephalophora
3
3
 When seeds turns brown and fall off easily
awned graceful sedge
Carex davisii
7
-1
 When seeds turn golden and fall off easily
curly-styled wood sedge
Carex rosea
4
5
 When seeds turn brown and fall off easily
long-beaked sedge
Carex sprengelii
9
3
 When seeds turn yellowish and fall off easily
toothwort
Dentaria laciniata
5
3
 When seed packet turns brown and the seeds black
shooting star
Dodecatheon meadia
6
3
 Mid-summer. When seed packet turns brown and the seeds loosen.
cow parsnip
Heracleum maximum
5
5
 When seeds dry
broad-leaved puccoon
Lithospermum latifolium
9
5
 In the fall, when the seeds turn hard as rocks.
common wood rush
Luzula multiflora
7
3
 Early summer, when the seeds start to dry.
wood betony
Pedicularis canadensis
9
2
 Early summer, when the seeds packets start to dry and open.
thicket parsley
Perideridia americana
8
5
 Early summer, when the seeds start to dry.
early meadow rue
Thalictrum dioicum
7
2
 Early summer, when the seeds fall off easily.
meadow parsnip
Thaspium trifoliatum
7
5
 Early summer, when the seeds start to dry.
golden Alexanders
Zizia aurea
7
-1
 Late summer, when dry.


Comments on selected species

Wild Leek: Although these seeds can be gathered easily in quantity, the trick is to map, mark, or remember where the plants are, as other vegetation is likely to hide them by the time the seed is ripe. Allium burdickii (narrow-leaved leek) ripens well before Allium tricoccum

It may be a stretch to put toothwort on the easy list. The seed is ripe for only a very short time, and you have to catch it before it falls. But once you do that and broadcast it, you’ll soon have a great many rapidly-spreading plants. 

Shooting star too requires a hedge on its “easy” rating. The Somme preserves have tens of thousands of restored shooting stars, and we didn’t put a lot of detailed work into them. The seeds are held high and are more-or-less easily visible when ripe, if you have recorded where to look. They won’t establish on bare soil; they need an open turf (whether annually burned bluegrass or big bluestem). And the last caveat is that it takes them ten years or so in the wild to flower. But then they’ll flower and seed year after year for decades or longer. Many spring species are slow starters. Woodland restoration for biodiversity conservation is not a mission for the short term.  

Medium list

Many species are on the “medium” list mostly because, for various reasons, only a few establish, despite our best efforts. But the populations then tend to gradually increase.

Common Name
Scientific Name
C
W
When and How to Gather
white baneberry
Actaea pachypoda
7
5
In fall
nodding fescue
Festuca obtusa
5
2
Mid-summer, when seeds dry
smooth wild licorice
Galium circaezans
10
5
Mid summer, when they detach easily.
wild geranium
Geranium maculatum
4
5
When they turn black
smooth Solomon’s seal
Polygonatum canaliculatum
3
3
In fall, when dark blue
feathery false Solomon’s seal
Smilacina racemosa
3
3
In fall, when red
starry false Solomon’s seal
Smilacina stellata
5
1
In fall
yellow pimpernel
Taenidia integerrima
9
5
In fall, when dry
large-flowered trillium
Trillium grandiflorum
8
5
Mid-summer, when fruits whiten
red trillium
Trillium recurvatum
5
4
Mid-summer, when fruits whiten
bellwort
Uvularia grandiflora
7
5
Mid-summer, when fruits whiten
yellow violet
Viola pubescens
5
4
When capsules fatten; check to see that seeds are black.


Comments on selected “medium” species

Baneberry and the Solomon’s seals present you with fruits containing many seeds. Is it worth it to separate the seeds from the gooey pulp? Or will natural processes (animals?) do that just as well? It would be great if some people experimented with both approaches and let us know the results. We sometimes broadcast whole fruits – and, if we have time, we sometimes separate the seeds. 

It takes careful marking or a good eye to find the seeds of woodland fescue. But if you find and broadcast, it should easily prosper. 

The seeds of wild licorice don’t do well in a seed mix; they’ll all stick together. We pick them when we see them and then move them to distant good habitats, where we walk along tossing out a seed at a time. Once a few have grown, animals will spread them for you. 

Trilliums and bellwort make fleshy fruits that turn from green to whitish when the seeds are ripe. We throw out whole fruits in new areas with the expectation that ants will then take over and distribute the seeds. (For more on ant dispersal, see Endnote 5.)

More Difficult

Some of these are among the more important spring species. Don’t hesitate to start with the easier ones. But in time, you’ll want to wrestle with these too – or identify a special person who’ll volunteer (or contract?) to rise to the occasion. 

Common Name
Scientific Name
C
W
When and How to Gather
wood anemone
Anemone quinquefolia
7
5

rue anemone
Anemonella thalictroides
7
5
Ripens over long period. “Massage” to remove ripe seed. 
smooth bank cress
Arabis laevigata
5
5

pussytoes
Antennaria plantaginifolia 
3
5

white bear sedge
Carex albursina
7
5

Penn sedge
Carex pensylvanica
5
5
When seeds are fat.
blue cohosh
Caulophyllum thalictroides
8
5
When fruits turn blue.
spring beauty
Claytonia virginica
2
3
May
Dutchman’s breeches
Dicentra cucullaria
6
5

robin’s plantain
Erigeron pulchellus
10
3

white trout lily
Erythronium albidum
5
5
Pods ripen on ground after leaves wither.
shining bedstraw
Galium concinnum
5
5

sharp-lobed hepatica
Hepatica acutiloba
6
5
Ripens in late May. “Massage” to remove ripe seed.
golden seal
Hydrastis canadensis
8
5

yellow star grass
Hypoxis hirsuta
9
0
When seedheads turn dry and fragile. Mark individual plants; otherwise hard to find.
false dandelion
Krigia biflora
7
3
Seeds blow away quickly on ripening. 
pale vetchling
Lathyrus ochroleucus
10
5
When seeds turn hard and dark
violet wood sorrel
Oxalis violacea
9
5

ginseng
Panax quinquefolius
9
5

broad-leaved panic grass
Panicum latifolium
5
3
Ripens over long period. “Massage” to remove ripe seed.
woodland phlox
Phlox divaricata
5
3
Seed heads explode. Gather when just drying (turning tan)
fire pink
Silene virginica
10
5
Seed capsules turn down shortly before opening and dropping seeds.
wood vetch
Vicia caroliniana
10
5



“Hey, Where’s the Flowers?”

Check out the above photo. Not all spring bloomers burst fourth at once. Yes, I’m inspired by lush flower photos. But I snapped this photo in honor of the inspiring past and future displayed here. The bloodroot (bottom right) bloomed a week ago and now has a seed pod starting to fatten. The shooting star (bottom middle) has buds and will bloom next week. The thicket parsley (finely divided leaves) will bloom in a few weeks, as will the golden Alexanders (bottom left and top right). Yellow pimpernel (top center) will likely bloom a couple of weeks later than the Alexanders. Trout lily (mottled, simple leaves covering much of the ground in the top third of the photo) would have already bloomed – but seems not to have flowered here this year. The competition was too great? Trout lily did bloom just off camera, nearby. In late spring, the cow parsnip (big leaves filling this photo’s center) will bloom, five or six feet tall, with a flowerhead a foot across. Blue-stemmed (top right) and elm-leaved (top left) goldenrods won’t bloom till fall. When you learn to know the plants by their leaves, you see the colors of past and future in your mind’s eye – and can be inspired by the richness of diversity – whether the flowers are in bloom or not! 
                                                                                                                             
Comments on selected species

Wood anemone: from seeds we’ve seen little result. But we haven’t tried hard. Though supposedly conservative, it’s fairly common in most of the woods where we work – in dense monotypic patches. We mostly “let it spread by itself.” We also “rescue” some plugs when a quality woodland is being destroyed. They can be planted out directly or installed in a wildflower garden, where they’ll spread and be a bountiful source of plugs. But in this setting, they seem to exclude most other plants, so we’ve been ripping them out. 

Rue anemone seeds are still ripe when green. Teasing the ripe ones out of the dense heads when seeds start to fall is challenging. Eriko Kojima recommends “massaging” the riper-looking heads to get seed. Even so, very few plants seem to establish from broadcast seed. We’ve had good if very slow results from rescued plugs. 

Many woods have surviving clones of pussytoes and may not need restoration help. That’s good, because our attempts to help have seen little success. The seeds blow around. Perhaps it just takes time.   

Blue cohosh seeds are easy to find but difficult to germinate. They are said to establish well from seed treated harshly for hours with acid. 

Spring beauty is already present in most woods. Controlled burning may well increase it as much as needed in a few years. If absent, it’s a challenge, as the seeds ripen and fall quickly – and are likely to be hiding down under everything else. It often grows in lawns but is mowed before seed set. If mowing is delayed, lawns can be a good source of seed. 

Though it’s common in many high-quality woods, we’ve had poor success restoring Dutchman’s breeches. Experiments continue. 

Robin’s plantain fares like pussytoes, above. Since seeds are hard to come by, we’re restored it through plugs.

White trout lilyis a very common species that may not need help, but if absent, it’s not one of the easy ones. We have gathered and broadcast them but not documented whether that has produced plants in new areas. 

Uncommon in our area, but very much present in the highest quality areas, shining bedstraw seems worth effort. We find little seed. 

Hepatica seeds fall soon after ripening. With seed broadcast, few plants emerge. 

Cx albursina: Seeds are hard to find, under cover, fall off easily.  They ripen in late May. 

Penn sedge produces few seeds, does not seem to establish easily. Can be readily established by plugs. Fortunately many areas have it, and it spreads inexorably. 

Wood vetch: H.S.Pepoon wrote in 1927: “Hillsides and dry open woods, frequent.” Now it’s rare. I’ve seen it only twice, long ago. Perhaps someone else can help with this one. 

Getting started

If you’ve read this far, you must be interested. Are you also concerned that this challenge is just too big? If so, we have a suggestion. Start small. The work explains itself and rewards us so deeply that we’re soon finding the ways to do more. 

Restoration contractors

In our experience, most contractors don’t know how to do this work for most species. Very expensive. Would become cheaper if there were more demand. 
Much seems to take the dedication that volunteers do.

Forming or working with a group

The group may be an existing land trust, or it may just be friends that are interested in this. This is the way to do it. The ecosystem is more complicated than a person can think, but we can get closer to what’s needed in this case by bringing together many people with different abilities and skills. Hunter-gatherer groups depended on a wide variety of skills, and we could emulate them. One person perhaps does the research. Other finds the best experts and mentors. Another makes plans. Another learns how to identify the more difficult species. (Everyone can learn most species.) Others may be good at and enjoy coordinating the collection of seeds, and storage, and broadcast. Someone may be good at helping everyone reach consensus and collaborate smoothly. 

Possible experiment

Some people report the impression that quality species establish well if broadcast into Penn sedge beds. Others report the opposite. Which is best? The same questions could be asked about dense patches of trout lily and other species. It would be helpful if a few people were to experiment and report. For example: broadcast seed into Penn sedge areas and bare ground (and tall goldenrod?) and see which species establish best where. 

Fabulous Disclaimers

1. As a number of reviewers reminded us: the summer and fall flora are much more in need of restoration than the spring flora. Yes, that’s true. Most stewards seem to know that, but it’s worth a reminder in a broadcast blog post like this. For posts on restoring summer and fall flora, see, for example: When and How to Plant Woodland Seed and Rediscovering the Composition of Oak Woodlands.

The point of the Why Restore Spring Flora post was that a few surviving non-conservative species, though beautiful, do not indicate a healthy woods – or even a healthy spring flora. So, spring flora deserves restoration help too. 
Some people perceive a scene like this as a “rich” spring flora. It is, instead, a superficially beautiful and admittedly precious but degraded “few culture” of mostly trout lily with a smattering of Penn sedge and a few other common early spring species. Trout lily survived and proliferated – perhaps becoming more dense than natural – as the summer, fall, and more conservative spring species were lost to such stressors as grazing, fire-exclusion, and (these days mostly) excess shade. 
2. Reviewer jwpboss helpfully pointed out: restoration should not focus only on rare species. We hope this post makes it clear that the whole flora merits restoration. But we can’t agree with jwpboss that the conservatives should be left till later. Some are easy to restore. Some seed sources are vanishing and may not be available later. The ecosystem may recover best with all elements present (even perhaps with a few especially common and aggressive species held back until later). And species that are rare today, after two centuries of stress and degradation, may once have been common and central to the community. Perhaps they will be once more, if given a chance. For more discussion of now-rare, once-common plants, see Plant Refugees.  


All Seasons Present and Accounted For
Unlike most photos in this post, the above shows spring, summer, and fall (also perhaps winter, if you include the handsome dead log). In bloom here are bellwort (yellow) and a smattering of spring beauty and toothwort. Later spring bloomers here include wild leek (wide leaves) and woodland puccoon (up against log). Early summer species here include the delicate long-awned woodgrass (bottom left and mid right).  Late summer species here include elm-leaved goldenrod (bottom mid right). By fall this plot will be deep under woodland sunflower, paired young leaves now showing here and there, for example, under the right side of the yellow-flowered bellwort. 

Endnotes

Endnote 1

From North Branch Restoration Project seed leader Eileen Sutter: 

Hello friends,
Just thought I would share with you my best knowledge about references for seed collectors in Cook county. There may be more that I don't know about. Here they are:

North Branch Restoration Project Seed Book:

Covers 15 grasses and sedges and 70 forbs from prairie, savanna and woodland habitats in the region with pictures and text. Lots of good information about when to collect, and what ripe seed looks like. Good section on diagnostic features which tells you how to differentiate lookalikes. No information on shrubs, trees. Limited number of species.

Field Guide to Seed Heads of Common Native Plants of the Tall Grass Prairie Region by Izabella Redlinski of the Field Museum

Covers 72 native woodland, wetland and prairie species, with clear pictures and helpful text on when a seed is ripe, best way to collect, etc. Emphasis on prairie species. No information on shrubs, trees. Limited number of plants.

More comprehensive (but challenging to access) is someSeed Collection Data from DuPage County-shared a few years ago on the Volunteer Stewardship Network listserv. It covers more than 500 species. See Endnote 4.

Endnote 2

If you look up in a woodland, on average you should be able to see 50 to 20 percent blue sky. If more than that amount of sky is obscured by leaves, the oaks and most of the other biota would not reproduce and thrive. A natural maple basswood forest would be darker than that, but the biota of that kind of forest does not magically appear when an oak forest is allowed to go dark. Instead, fewer and fewer oak woodland plant and animal species would thrive. Tree reproduction might be by wind-blown maple, basswood, elm, ash (formerly), box elder, etc., but in many cases, woody plant reproduction would largely be by multiflora rose, buckthorn, honeysuckle, and the like.  

How many and what kind of trees should you cut, if you want to restore health to an oak woodland? This is not settled science and perhaps will never be. Situations differ and times change. But a basic principle that many people now follow is to reduce the canopy sufficiently to allow reproduction and sustainability for the biodiversity-significant species. Thus the question is more, how many and what kind to retain. 

Bur oak requires more light than the others. If the old trees are bur oaks, then presumably the soil biota and other species are adapted to the amount of light that it takes for bur oaks to reproduce. In bur oak woods we cut out most of the basswoods and often most of the hickories and red oaks. If bur oaks have reproduced as dense stands of “pole trees” – we cut them too and let them re-sprout. 

White oak woods are thought to be naturally a bit darker. We’d leave a few more red oaks, but we’d especially open the canopy in areas where young white oaks were seeing their lower and mid branches being shaded out. 

One good way to reduce the canopy of large trees is to girdle them in June. That method requires no herbicide and “works over ecological time” rather than all at once. The decaying trees will be a boon to woodpeckers and many other species. They may fall gradually and burn up in the regular controlled burns. 

Dense small buckthorn (or dense anything) seems best to cut and burn in bonfires. The most practical and least damaging time to do that is fall and winter when the ground is dry or frozen. 

Also, if large numbers of buckthorn, maple, or ash seedlings are present, it may be most efficient to foliar spray them with herbicide during the growing season.

If large areas are opened up too quickly to bare soil, the result may be dense tall goldenrod, briars, or more buckthorn. These can resist next restoration steps, do not carry fire, and can lead to another round of small brush. Sometimes we open the canopy enough to allow the herbs of darker woodlands to thrive and reduce the canopy more later, so that we can seed into an existing turf. But there seem to be no simple solutions that work everywhere. 

Endnote 3

(wetness) and (conservativeness) numbers.

For fuller explanations of the C numbers check out Swink and Wilhelm (1994).

But, simply stated, a plant with a “W” of “-5” is found mostly in standing water or where it is very wet (like a cat-tail or a water lily) and a “+5” is found on the uplands. The other numbers represent the gradations in between.

Wetness rankings are more discriminating at the wetter end of the scale. On the dry end, prickly pear cactus and porcupine grass are ranked 5, but so are such mesic species as blue cohosh, Penn sedge and rue anemone.

A C of 9 or 10 indicates a species that would rarely be found outside of a healthy, high-quality natural ecosystem – but might be among the commonest plants there. A plant with a C of 0 or 1 would be found mostly in degraded areas like roadsides or recent bulldozings. The other numbers represent the gradations in between. A few 0 or 1 plants might be found in a high-quality ecosystem, for example on the edge of a coyote burrow. 


Endnote 4

A recommendation from Eileen Sutter, North Branch Restoration Project seeds leader: 

The Excel spreadsheet from DuPage County that was distributed by the Volunteer Stewardship Network. No pictures, only text. Most comprehensive species coverage in the region, with over 500 species, including trees, shrubs, and many sedges. Gives detailed habitat information, flowering time, flower color and seed collection time. No pictures, no diagnostic section. A bit unwieldy to use because of amount of data. Information on far right side of the spreadsheet covers post-collection seed treatment and uses abbreviations; difficult to decipher without a key in the spreadsheet. Yet, seed collection and flowering time plus habitat information for so many species makes this useful.

This impressive Excel spreadsheet would not paste into this post. We are looking for ways to link to it. We have a copy, if anyone could put it up on a website that could be linked to. We seem to be cyber-limited.

Of course, much of that info would not be helpful outside northeastern Illinois. Do people have other good sources that they could recommend to readers of this blog?

Endnote 5

Many species that mature seed in spring have an impressive adaptation. Attached to the seeds are little or big glistening "bodies of fat" (technically called elaiosomes). We also call them "ant candy." Once when I was planting a seed production garden, I stopped to explain this phenomenon to folks, and when I looked back at the planting, all my seeds were already moving elsewhere in the jaws of ants. People were impressed.

Part of our reason for planting such seeds as soon as they're ripe is to give ants a chance to put the seeds through this process. (But see the second to last paragraph.)

I don't know what it is that makes the spring species see this as such a good idea. Perhaps the literature has an answer to that somewhere. But one experiment we did long ago suggests one possible answer. We put trillium or bellwort seeds into a "pet" colony of prairie mound-building ants (Formica montana) that were living behind glass for observation. The ants kept those seeds underground (all summer?) and then suddenly put them all out into their trash heap. Perhaps the seeds give off a chemical that triggers that action. Perhaps the seeds benefit by being kept underground for a while.

Certainly a plant benefits from having the ants haul the seeds some distance away from the parent plant. Perhaps dispersal is the whole benefit. Some people have expressed concern that if the elaisome dries out, the reproduction of the plant will suffer. Is there evidence for this? There are numerous articles on elaiosomes that pop up on Google, but I couldn't find any about problems with planting with them dried out, so perhaps there's no problem. We seem to remember we've seen seeds germinate and establish just fine after eliasomes dried out. So, yes, we put out many of such seeds as soon as ripe, going with nature's flow. But we also save many (if we have a lot of that species) to put in later mixes, so they'll be more widely dispersed, with a belief that they'll do well. To become more sure that we're treating our seed as well as possible, research is needed (and perhaps the basic research has been done, so all we need is the book or web research by someone checking the literature?). Can anyone contribute?  

Jim Steffen from the Chicago Botanic Garden makes an interesting observation in his blog: "I often get questions from people who have planted ephemerals in their yard, but say they don’t see seedlings, while their neighbors are finding them on their property. It is more than likely that the neighbors have the ant colony that is harvesting the seed and sowing them at the neighbors'." Spring seeds are fun. 

Acknowledgements

Thanks to Eileen Sutter and Gayle Laboda for helpful suggestions.

Table basic info courtesy of the Universal FQA Calculator.

Thanks to Kathy Garness for generous, tireless, proofreading and edits.


11 comments:

  1. If trillium remain clumped after several years of blooms, does this suggest the right type of ant is not present?

    How do you recognize when it's time to collect seed from bloodroot?

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  2. To Ryan: In my experience, trillium clumps get bigger and bigger as long as there's little competition (and deer don't eat them). Their seeds are dispersed by ants. Wilhelm and Rericha (2017) list eight species of ants known to disperse the seed. Common yellowjackets also disperse the seed.

    Bloodroot pods get thicker than green beans before they're ripe. One way to get the feel for how big they need to be is to watch until a few begin to open by themselves. When ripe, the seeds are deep reddish brown. They too are normally dispersed by ants.

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  3. Thanks. You've prompted me to order Wilhelm and Rericha.

    This link says ants will disperse the seeds up to about 7 feet, while wasps carry them further.
    http://botany.thismia.com/2009/09/27/welcome-to-my-botany-blog/

    And a paper online suggests deer as a longer-range vector.

    I'm interested in the question generally, and also particularly for the trillium and bloodroot in our yard, both of which disperse < 4" / year. With 8 species of ant vectors, it seems likely most reasonable-sized preserves might retain 1 or 2. But probably not our yard.

    Our plants were here before we moved in, so I can't say they're locally native. I may try to hand-disperse as an experiment, but just in the yard.

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    1. Cripe. The "book" arrived. I guess i should have expected something the scale and style of the OED. Leafing through while it rests on my lap i can feel the strain on my ACL.

      I'm going to need to do what my grandfather did with his dictionary--get a dedicated stand with a lamp and magnifying glass.

      "Bouquets of trillium often emanate from the middens of ant nests." That's poetic for an encyclopedia.

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  4. On Bloodroots.
    I have gathered seed and planted the seed the same day several miles from where gathered. I planted the seeds on the edge of a driveway thru a hardwoods area. I watered them well for about a month to make sure they where kept moist. They germinated and still come up every spring but after 3 years no flowers yet. I do have other bloodroots in the area I transplanted that are doing fine and are spreading.

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  5. Any thoughts on burning woodlands. Once the woods are thinned the under story of small trees/shrubs takes off and keeps the fuel level low. Is the establishment of grasses and forbs on the ground an urgency so that there is fuel to keep the small trees/shrubs at bay with subsequent burns? Smaller trees/bushes are easy enough to remove before seeding but the really small say under 8" seedlings can number in the dozens per square foot. Manually removing these either with selective herbicide treatment or pulling is way too time consuming.

    I have found that Sugar Maple seedlings are easily eliminated by small leave litter fires in early spring before anything starts growing or late fall/winter after everything is dormant. Spraying with herbicide is a poor choice as many tree seedlings will not leaf out till well after early spring plants are up and going thus killing the few existing spring plants that maybe present.



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  6. To Anonymous May 23: I generally agree with your concerns and suggestions. We often spray buckthorn etc. seedlings in the summer or fall. Often the only surviving natural flora is the spring ephemerals - which would not be damaged by summer or fall spraying. If there are a few Culver's roots, wild coffees, or other natural summer plants surviving, we might cut them before spraying; they then re-sprout and thrive in the reduced competition.

    We don't have good experience in woodlands with efforts to rapidly establish grasses for fuel. Under oaks, the oak leaves are sufficient fuel, so the grasses and sedges are just a plus, as they increase slowly. But if there aren't enough oak leaves to carry a fire, we tend to have problems with brush re-establishing. We're experimenting with seeding "intermediate species" (not too shady, not too sun-dependent).

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  7. I noticed you omitted the most common of early spring flowers, the Mayapple (Podophyllum peltatum).


    Do you consider the poor Mayapple a thug like woodland sunflowers and not worthy of mention??

    Why no love for the Mayapple?

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    1. To Anonymous: May 26. We have sometimes thrown a few mayapple fruits around established areas that didn't have it. But we mostly don't restore mayapple for two reasons. The first is that it's already widely distributed in our areas. Second, yes, it is a thug - in the sense that it has the tendency to crowd out most other vegetation in some situations. In some situations, dense mayapple clumps look "bombed out" when the foliage dies in mid-summer. Perhaps in high quality areas mayapple doesn't behave that way? Or perhaps it's a natural and temporary phenomenon?

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  8. Blue cohosh. I'll give my anecdotal success. I gathered some seed from a very degraded site several years ago. I collected seeds in early fall, removed the pulp from the seeds, washed them. I immediately planted the seens all around our lot, poking the them 1/2 to 1 inch into the ground in places I thought they'd do well. They came up in abundance two springs later everywhere I planted them. The seedlings are robust. The same approach works for baneberry and horse gentian, though the latter has lower germination rates, and some seeds still germinate 3 and 4 years after planting...so maybe hot water or acid would help there.

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  9. Thanks for the good comment. Some people treat cohosh with acid. It's great to hear you had such good success - by just waiting for for natural processes to get these seeds ready. Woodland restoration is for the long haul. Waiting a few years for some species to germinate seems like a reasonable part of the process. I wonder what would have happened if you didn't remove the pulp. Perhaps just another year's delay? Or what?

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