Bulbs for Continental climates, Upper Midwest--TOW

Mary Sue Ittner msittner@mcn.org
Mon, 21 Apr 2003 07:32:05 PDT
Dear All,

This weeks topic of the week continues our theme of discussing which bulbs 
can be easily grown in the ground in different climates. We started with 
Bulbs for the Pacific Northwest and followed it with Bulbs for 
Mediterranean climates. Cynthia Mueller has promised to organize something 
for Texas in the future and if any of the rest of you want your situation 
discussed and are willing to organize an introduction please contact me 

Boyce Tankersley has provided the Introduction for this week's topic with 
an extremely interesting and complete picture of what has been successful 
in the Chicago Botanic Garden. Thank you Boyce and I look forward to 
hearing from the rest of you in this area about what grows well in your 
gardens. It always fascinates me what parts of the country are included in 
the term "Midwest."

Mary Sue
PBS List Administrator and TOW Coordinator

Bulbs for Continental Climates: Upper Midwest

As an avid gardener, I am constantly attempting to expand the list of bulbs 
hardy to this area through experimentation (or to grow better looking bulb 
displays of bulbs known to be hardy than my neighbors). The thrill 
associated with 'documenting' a new species of bulb hardy in this climate 
is similar to the thrill of seeing a new species in the wild for the first 
time (or getting the first kiss). It only happens once; it is a source of 
great pride (and no little bragging); and it is a memory to relish when the 
years get long and the joints start to get stiff. For the purpose of this 
introduction however, I am only going to cover the bulbs reliably hardy at 
the Chicago Botanic Garden and will depend upon other members of the group 
to relate their triumphs.

Bulbs grown out-of-doors, regardless of where the garden is located, are at 
the mercy of the local environment. For the most part those that survive 
and thrive originate from environments with similar climatic extremes.

The climate of the upper Midwest of the United States is described as 
having a continental climate. In brief, this means there are no large 
bodies of water sufficiently close to the area to moderate climatic 
extremes. This area enjoys seasonality with large changes in temperature 
(approximately 100 degrees F difference between winter lows and summer 
highs), length and intensity of the photoperiod (10 or less hours in 
winter, 14 or more hours in summer), precipitation (16 inches annually 
along the western edges of the area, 40 or more inches in the wetter 
eastern areas), relative or atmospheric humidity (on any given day can 
range from near 0 to 100 percent) and wind speed (from calm to hurricane 
force winds). An anonymous native remarked to an immigrant in the 19th 
century that if they didn't like the weather all they had to do is wait a 
few hours and it would change.

For readers interested in learning more about the climate that dictates 
what bulbs we can easily grow, I recommend two sources.

For those with short attention spans, the USDA climatic zone map is based 
upon average winter low temperatures. It identifies the area of the Upper 
Midwest as falling into zones 6 (south) through 3 (north).

A more in-depth description of the climate can be found in the Sunset 
National Gardening Book. The zones in this publication are based upon a 
wider range of criteria and the information accompanying each zone 
description is very good. For the Upper Midwest, zones under discussion are:
·       35 (Ouachita Mountains, Northern Oklahoma, Southern Kansas to 
North-Central Kentucky and Southern Ohio)
·       39 (Shoreline Regions of the Great Lakes)
·       40 (Inland Plains of Lake Erie and Lake Ontario) on the east.
·       41 (Southeast Nebraska and Northeast Kansas to Northern Illinois 
and Indiana, Southeast Wisconsin, Michigan and Northern Ohio)
·       43 (Upper Mississippi Valley, Upper Michigan, Southern Ontario and 
·       45 (Northern Minnesota, Northwestern Wisconsin, Eastern Manitoba, 
Northern and Central Ontario and Quebec)

Any garden within this area can experience the full range of any of the 
climatic variables within a short period of time (hours).

The data I am reporting in this introduction comes from the Chicago Botanic 
Garden. This Garden has been open to the public for 31 years and has had a 
garden devoted to the growth of bulbs since 1983. A recently adopted Plant 
Collections Policy identified the goal of creating a nationally recognized 
collection of Narcissus and regionally significant collections of Iris and 
Allium. Much time and many resources will be needed before these goals are 

For the purpose of this introduction, I am giving a synopsis of the bulbs 
that relatively perennial. A full inventory of all of the bulbs in the 
Garden can be obtained by using the Searchable Database within the Living 
Plant Documentation department on the Chicago Botanic Garden website 
(http://www.chicagobotanic.org/). Also available on this website is a list of 
'What's In Bloom' that is updated every two weeks throughout the year.

The name Chicago is derived from a local Indian tribe name for 'stinking 
onion' and the Garden displays a number of Alliums used in our ornamental 
displays. In general our cultural practices do not encourage the 
naturalization of this genus and we do have problems with rot where Alliums 
are interplanted with summer annuals that require high levels of 
irrigation. Even in the areas that have the least amount of summer 
irrigation the taxa from Central Asia are not long term perennials.

Alstroemeria 'Sarah' is one of our bragging points. Initially planted as an 
annual in the mid-90's, several plants missed the rototiller and have 
happily survived our winters and rewarded us with flowers ever since. The 
need for more research is suggested. Anyone else have Alstroemeria that are 

The genus Anemone is represented by native and introduced taxa. In this 
Garden the introduced taxa (blanda cultivars) are heavily predated by 
chipmunks and squirrels. The native taxa are wonderful features of our 
natural areas but can be a pest when in seed.

Arisaema, other than the native triphylla, are relative recent additions to 
the Garden but are proving more hardy than the literature suggested. Their 
tendency to come up later in the season may be a key attribute in their 
hardiness in this area.

The Arums, with their tendency to start growth in fall and carry it through 
the winter get beaten up by our cold dry winter winds when snow cover is 
lacking, and, I suspect, resent the summer monsoons that accompany the 
remnants of hurricanes that have landed on the Gulf of Mexico. They hold 
on, but just barely, and are much more attractive in the more southern 
reaches of the Upper Midwest.

Belamcanda and the closely related Pardancanda are at best biennials in 
this climate. Seed production is key to keeping good displays of either 
genus in our Garden.

Brimeura amethystina has suffered from use only in annual displays. Having 
said that, it appears to be winter hardy, surviving fall plantings and 
blooming well the following year.

Bulbocodium vernum is one of those bulbs that I did not know before moving 
to Chicago, and after checking the references, I am surprised that it grows 
as well as it does. It doesn't appear to reseed but the bulbs have grown in 
our Bulb Garden since 1993.

The Camassia's are native to this region and all of them perform very well. 
They apparently appreciate the heavy clay soils and the summer moisture.

Cardiocrinum, an addiction of mine since I first saw them in flower at 
Inverewe Gardens on the northwest coast of Scotland, still elude us. In the 
best of gardening traditions, we continue to order small quantities and try 
them in different areas of the Garden. Other gardeners in this region boast 
of success and I anxiously await their descriptions of the conditions under 
which they get this queen of the bulb world to flower and naturalize.

Chiondoxa thrive, reseed, hybridize, and perennialize in this Garden 
despite being predated by deer, rabbits, chipmunks and squirrels.

Claytonia virginica, harborer of early spring, is a native of our 
woodlands. Unfortunately it is missing from our Garden flora.

Colchicums deserve to be more widely planted. They are reliably hardy, 
resistant to predation, and can be either fall blooming or spring blooming. 
The spring bloomers are not as large as the fall bloomers but the masses of 
flowers more than make up for the smaller size (a little larger than hybrid 
Crocus). Colchicum kesselringii spawned hundreds of seedlings several years 
ago and their growth is much anticipated this spring.

Corydalis that form bulbs or rhizomes have both proven to be hardy in the 
Garden. Those that have not survived in the trials have either suffered 
from frost-heaving or from predation by rabbits. Corydalis pumila has 
reseeded around the trial plants.

The Garden has not experimented with any Crinum outdoors.

Crocosmia deserves a more intense evaluation in our Garden. A number of 
corms have escaped the rototiller and have reappeared for a number of 
years. The range of new colors available and their ability to survive over 
time suggests an opportunity.

Crocus are a charming part of the Garden, but must be supplemented to 
maintain good displays. Predation is certainly a factor but heavy wet 
summer soils and late spring frosts also take their toll. In the southern 
end of the region Crocus tomasinianus naturalizes and survives in spite of 

Cyclamen dislike the heavy mulches used to control weeds and are 
particularly sensitive to heavy wet layers of large deciduous leaves in 
late fall and through winter. An informal trial is underway to see if they 
survive long term under a grove of Juniperus virginiana, and initial 
results are promising.

Eranthis thrive and reseed, though not vigorously. The seedlings apparently 
prefer the bed on the other side of the path.

Eremurus have survived and thrived in select locations and we continue to 
search for additional locations that they will live in. They seem to favor 
south and west facing walls and locations where the tender growing point 
will not be trampled during the dormant season.

Erythronium when in a 'good' location increase in size of clump and are 
good perennials. Unfortunately there are a number of not-good locations 
where they would be spectacular if they would only survive. They don't 
appear to reseed.

The Fritillarias appear to be much more tolerant of our conditions than 
their native ranges would suggest. The tetraploid selections of imperialis 
are much better perennials than their diploid cousins. This suggests that 
perhaps a little colchicine on some of the other species might result in 
some interesting improvements for the Garden.

The snowdrops, Galanthus, are reliably hardy in this Garden. The plants 
supplied by commercial growers in the past have been a random mixture of 
species. This makes for a prolonged display but drives documentation staff 
like myself bonkers.

Hyacinthoides or whatever name this bulb currently passes for, is a short 
lived perennial. It would be interesting to obtain some seed from native 
populations at the extreme edge of this taxon's range to see if hardier 
clones could be found for this climate.

Ipheion, subject of recent discussions on the listserve, are hardy but do 
not multiple readily. The cultivar/undescribed species 'Rolf Fiedler' has 
not been tried outdoors.

The bulbous Iris thrive in this climate. Clumps increase to delightful size 
and the blooms/foliage is not heavily predated. Incredibly tough, the 
flowers fly through late cold snaps and snows with little damage.

The bearded iris suffer from Iris borer but yet thrive. Amazingly tough and 
adaptable plants.

Iris bucharica is the only Juno that has successfully been grown for a 
number of years. In the right location it clumps up nicely. No viable seed 
has been found to date, perhaps the Garden needs a second clone? Several 
other species are informally under evaluation and the jury is still out on 

Siberian iris thrive where many of the Japanese cultivars do not. Louisiana 
types survive but do not flower with the same vigor as they did in the 
southern end of the range.

Leucojum are reliable perennials and increase clump size over time. No 
seedlings have been observed.

Lilium is the subject of a new breeding program at the Garden. Most lilies 
are hardy to this climate and if the deer, rabbits and viruses can be held 
at bay are great garden plants. The tetraploids are resistant to viruses, 
so far, but still favored food for deer.

The Lycoris are much hardier than their native ranges would suggest (or 
perhaps our knowledge of the climate in their native range needs to be 
improved). At the Garden, only Lycoris radiata has not proven to be hardy. 
Taxa that produce winter foliage are not as vigorous as those that produce 
foliage in the spring.

Muscari, with their strong tendency to produce leaves in the fall and carry 
them through the winter are not as nearly as vigorous as they are in the 
southern end of the Upper Midwest region. Flowers are good, reseeding does 
not happen.

Narcissus, particularly trumpet, large cup and small cup are well 
represented in the collections. Almost all clump up nicely over time. At 
least one of the species, Narcissus asturiensis, has grown well in the Bulb 
Garden for the last ten years. Narcissus bulbocodium and cultivars do not 
survive well, and rarely flower a second year.

Nectascordium siculum has graced the Garden for the last five years.

Not many Ornithogalum have been tried. O. umbellatum is only slightly less 
weedy here than it is in the southern end of this area. O. balansae from 
the Caucasus is showing great promise.

Puschkinia and Scilla all are good perennials and reseed, in a nice way, 
around the original plantings. Deer and rabbits graze them but the sheer 
numbers guarantee success.

Tulips are beautiful annuals and some can form perennial clumps that 
produce flowers over time. In areas with sandier soils in Michigan tulips 
are grown commercially. Outside the Garden, where the mandate to interplant 
with summer annuals does not result in frequent summer irrigation, some 
species and their cultivars show promise of becoming true perennials.

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