A whole family of California Quail totter over the garden: daddy stands watch on top, upper right.
There is no better way to ensure you finish designing a new basket than to put all of your eggs in one.
This winter I have been building a 1000 square-foot (100m2) greenhouse to produce hardy native and rock plants and replace my backyard hoop nursery. I was unable to find anyone who has already tried to make a passive solar (self-heating and cooling) greenhouse but using traditional materials that nursery people are familiar with. (Most passive solar greenhouses are serious things, framed in wood like a house or shed whereas most production greenhouses are metal frames wrapped in plastic film.
I aimed to create a hybrid: something economical enough for a business- like my own- to reasonably use. This means lighter materials. (versus concrete floors, glass roofs, et al, of a long-term and serious greenhouse). There are also no utilities on site, so being off-grid is not solely to prove a point.
The dark truth and problem with greenhouses is twofold: They consume prodigious amounts of energy to heat and cool (usually propane of natural gas). In America, the average greenhouse costs four times that of a house to heat/cool. Secondly, a traditional greenhouse is a needy, fussy, fragile bastard teetering on disaster all the time. A brief over/under-heating, usually from a power outage or vent catching or door left open, can result in damage or loss to everything in there. This shit kept me awake at night when I worked in commercial greenhouses.
So the drive to create something better is both environmental and mental.
So we built it from scratch in the old-school way that the last generation of Colorado nursery-people did: bending fence rail into hoop ribs and building the ends by hand. A hoop-house on steroids kind of deal. It is inside of such things that my mentors have produced all of the cacti, native plants, and trees… where I worked for years and where for years later I have purchased the plants for my gardens. These humble greenhouses are the workhorses behind all the things we love.
Anyhow, I found myself inventing a wheel- a prototype and F.O.K: First of a kind. I have not finished and I don’t have the answers. Yet. But I want to share some main lessons so far.
Heating:
For economy and sanity, it’s not dug in. It’s powered only by water. IBC totes. I hadn’t seen anyone use those before so I’d like to take credit for that idea if nothing else and the rest of this folly ends in tears. 20 of them gives me 5500 gallons (21,000L) of water as a north wall, well above (50%) the average used in passives. (per square foot of growing space).
Insulation:
I was going to make a straw-bale wall as the north side’s insulation but that grew more painfully more complex than useful. Instead, there are 2”-thick rigid styrofoam boards (salvaged) which would have cost $600 new, half that of using straw. Next winter I want to try hanging infrared reflective foil behind the water totes and measure the efficacy.
One of the most heartening surprises has been how well the size, proportion, and two layers of film are working, getting me off the hook for further insulation. Usually, insulating the ground around the perimeter of a passive greenhouse is important, but the proportions of this one seem to be mitigating that. This is a huge win towards my goal of creating something that is not a complex pain for other growers to do.
The floor is simply black (heat absorbing) groundcloth on top of compacted gravel fines. Wherever possible, I’ve used salvaged, used, or free materials. While it’s an experiment, it needs to pay itself off some day.
Glazing:
For sanity the outside skin is one whole piece, as it will have to be replaced every 4-8 (or 10) years. The proportions are about 50x25, (15x7m) so the ends are theoretically big enough to vent it without side or peak vents. There is no electricity, so no extractor fan per se, but I will try solar-powered circulation fans which can be directed toward aiding the convection cooling.
The Biggest pain in the Ass and one tentative regret
Two film layers. Traditionally these are laid together and a fan inflates them apart, operating perpetually for the whole life of the greenhouse, creating that critical insulating and structural airspace. Without electricity on site and a learned shyness to risk so much on electronics, I avoided that and had to build an interior wooden intra-structure to hang my second layer. It’s been a pretty flexible, easily adaptable system but a hell of a job to do: lots of hours and lots of exercise climbing ladders with a drill. I think if I were to do it over, it may have actually been easier to engineer a solar-charged battery-powered blower fan, rather than engineer the whole greenhouse.
The Regret?
At the moment, I feel that if I were to do it over, I’d use a kit greenhouse (without the heaters and motors) and retrofit one for ease of framing. But I’d shop around hard to see what brand or design would be sanest to retrofit. After all, more and more growers are not building their own from scratch but using modal kits. So far, materials have cost exactly what a kit greenhouse would cost of that size. ($6700) I’m taking that as a win. Hell, it’s bigger than our house.
Snowload:
Most of the greenhouse sheds it fine, but there is one hoop whose curve isn’t right, and it accumulated a heavy snow in part also to an interior purlin acting as a dam. I’ve moved that purlin to solve my problem, but to any future builder I’d recommend going gothic shaped for any film structure wider than say 10’ (3m).
-Ventilation is yet to be seen. I’m building these now, and their proving time is spring and summer. Stay tuned.
-Cooling will be a multi-part thing. Wax-opener powered and convective Passive vents, shadecloth (on the outside of the greenhouse- this is critical) over the growing area, a shadow over the water wall, and we’ll see what evaporative cooling happens from plants and floors.
All the water and two layers of plastic are doing the trick. Outside temps around 5F (-15) made it freeze inside the unfinished greenhouse, sending a tomato plant, a “canary crop”, to its maker. Even when unfinished and before I sealed air leaks, the greenhouse’s coldest was 22F (-6C), which to its credit is 20F (10C) warmer than a 2F(-16C) outdoor temperature, and no sun for days. It’s sealed up snugly now.
I wonder if it would have frozen had it been fully glazed. The water tanks have never frozen, lingering in the 40-50 (4-10C) range so far. A tray of cilantro is growing like a chia pet even through the solstice. Hardy woodies and semi hardy agaves are all sleeping like beauties so far. The greenhouse refuses to go below 35F(1C) which is pretty ideal for sleeping hardy plants. Without ventilation it peaks at 75/80F (24/27C) on a very sunny 45F (7C) winter day.
Cherries on top:
The greenhouse project became a village affair to finish in time for snow and deep cold; I had some back trouble that required friends to help out a day or two now and again, which led to having a thank-you solstice party with the aid of my friend Marla, which in turn led to a sort of a decorative Altar/shrine (after all, it is a plant-church!).
The greenhouse’s landlord insisted we re-use an old woodstove which had been sitting around gathering snow. While, for reasons of physics, a woodstove cannot actually heat a greenhouse in earnest, it will be useful to warm a corner of the greenhouse next to the potting bench on winter mornings (which might otherwise be 40F(4C) in there) to something comfortable for me to work sowing seeds and potting plants. It’s also just really nice.
{Well, I say it’s no way to heat a greenhouse, but what organically came up in conversation and now sits in my mind like an inevitable, potent, explosive seed, is the concept of running a passive water radiator coil from the stove and through the water tanks, which could hold the BTUs of heat from a single stove firing for weeks... Yet another passive system with high payoff that may be too fun not to try, even though the greenhouse will probably not need additional heat… stay tuned for that madness next winter}
I want to end with thanks: To my endlessly supportive greenhouse landlord. My ex-coworker did lots of tedious prep work on materials throughout her year working for me. I’ve also received generous advice on many occasions from folks including Kelly Grummons, Mikl Brawner, Jeff O, Dare Bohlander, Shane Smith, my neighbor orchid-Steve, John Stireman, the three musketeers of Minneapolis (you know who you are) and especially Tony Urschitz. My bible has been a gift from my other neighbor Steve: the cookbook for making passive greenhouses, Lindsey Schiller’s “The year-round Solar Greenhouse” Thanks to that second Steve, as well as Iain, Trina, JC, Hannah, Eric, and my endlessly patient partner Tori for lending a hand when I really needed it. I owe you all plants now.
2023 so far:
Manhattan Chapter NARGS (Zoom) Jan 16: Crevice gardens but mostly plants for them.
Utah Green Industry Conference (Salt Lake City) Jan23: Back to back crevice and no-water talks.
Christchurch Botanic, New Zealand, Jan 27, afternoon crevice workshop in the Rock Garden with Grant.
Landscaping with Colorado Native Plants Conference (zoom) Feb 25 Real Unwatered Landscapes
High Plains Landscape Workshop (Fort Collins, CO) March 4 Home Meadow Gardens
Durango Botanic's Gardening with Climate Change Seminar: Mar 9, 11 or 16 tbd, How to make a Future-proof Crevice garden
Spring Fever Symposium, Iowa Arboretum, Des Moines, IA April 15 2 talks: Crevice gardening for the midwest and favorite plants
Tucson Cactus and Succulent Society, Tucson, AZ Nov 2: Desert+Cactus Crevice Gardening
Buddies: Isaiah, Jacob, and John during conferences last year.
These are species I have grown without irrigation, in crevice. I am sure there are more. There are a few things that seem to require being in either/both crevice and unirrigated.
Know that a "rock garden plant" is subjective, and usually comes down to size and habit being appropriate with your rocks. Plenty of these are too large for a small crevice garden with small rocks and are noted as such. As with any unirrigated garden, performance and show will vary with rain and weather year to year... just like nature.
Keep in mind that different parts of a crevice garden receive/repel more or less runoff, so plants specific to those are noted. Soil type effects things, too. Generally silt and clay hold more water longer. Also know that all plants will need supplemental (at least weekly) irrigation the first season to get established.
Also know that Bob Nold’s ‘High and Dry” is basically an encyclopedia of plants that can grow without irrigation in Denver (and this classic book has a rock garden plant chapter). We are a little more limited over here in the hotter/drier Grand Valley.
So here it is. I'm listing possible sources after some and at the end listing several plant sources.
Plants for the unirrigated crevice garden in Colorado.
(below 6000’asl, like Grand Junction and Denver)
Flower power
Castilleja integra, sessiliflora. C. miniata in shade/wetter. (seed mailorder, or DBG sales)
Physaria ovatifolia, fendleri, arizonica, and most others but alpina. (Harlequin, Alplains, Nargs)
Phlox nana (not a tiny plant, it creeps.) (High country, etc)
Phlox hoodii (tiny) (rare)
Scutellaria resinosa (in a wetter spot, Denver not GJ, not tiny) (wholesaled by bluebird)
Melampodium leucanthum (not tiny) Plants of the SW, etc.
Zinnia grandiflora (spreads a lot, large gardens only- it will eat your small CG for snack) Plant Select.
Arenaria desertorum hookeri (seems to like afternoon shade) (Nargs, Waterwise, Chelsea)
Astragalus utahensis (short lived with organics in soil) NARGS seed
Astragalus spp, so many other western ones. Nargs, Alplains
Heuchera pulchella, abrahmsii, rubescens, even ‘Firefly’ (in deep shade and or with good runoff)
Ephedra minima/monosperma/regeliana in Denver, not GJ. Spreads by rhizome! (Chelsea, etc)
Liatris punctata- maybe too large for small gardens. Plants of the SW, seed, etc.
Phemeranthes (Talinum) brevifolium, parviflorum, calycinum, sediforme (capricious, sometimes brief.)
Lewisia nevadense (Nargs, etc)
Oenothera caespitosa (up to 1-2’, some forms are rhizomatous, most are short-lived)
Oenothera howardii (up to 1’ wide) Alplains, Harlequin
Atriplex corrugata (Hates water, ultimately a short shrub, plant in early/late winter) Chelsea
Woody lilies
Yucca nana (mailorder)
Agave toumeyana bella (mailorder)
Agaves, most hardy sp, let’s be honest.
Nolina greenei is the smallest/hardiest “Beargrass” but big: best behind the CG. (Coldhardycactus, high country, Chelsea, etc)
Lil yellow daisies
Stenotus acaulis (seedexes)
Haplopappus armerioides (alplains, seedexes)
Tetraneuris (Hymenoxys) acaulis, scaposa, and argentea
Calylophus lavandulifolius, C. serrulatus
Heterotheca jonesii (seed, nargs)
Heterotheca ‘GoldHill’ (available on front range of CO)
Erigeron liniaris (may need to be low/wette)
Lil other daisies
Townsendia hookeri (the best/longest-lived), T. glabella (big-ish), T. spathulifolius, T. incana, etc.
Erigeron tener (super) (nargs)
Aster ericoides ‘Snow Flurries’ can be 2’ or more wide. (bluebird wholesales this)
Erigeron compactus (come. to. daddy.) Nargs
Artemisia frigida- will get too big for some gardens. (seed, Little Valley, etc)
Eriogonum caespitosum, kennedyi, wrightii (small ssp), jamesii, pulchrum, and more. (NARGS, Harlequin, Waterwise, etc)
Eriogonum umbellatum (ie Kannah Creek) in wetter/shadier spots in Denver (commonly sold)
Eriogonum ovalifolium, all spp except niveum. (seed)
Eriogonum heermanii (ie, var sulcata) - fantastic. (nargs, alplains)
Some Eurasians for ya
Acantholimon spp, especially blue leafed ones, not alpine or green-leafed spp. (nargs, wrightman, etc)
Limonium minutum (nargs seed)
Goniolimon sp that fit in size. (harlequin, nargs)
There are surely countless others species yet to be tried…
Aloinopsis spathulata (Ethical Desert, etc)
Nananthus transvaalensis
Lil Cactus duh
Escobia sneedii, leei, orcutii, villardii, and probably any hardy sp. (Coldhardy Cactus.com, etc)
Escobaria missouriensis, vivapara especially. (many cactus retailers)
Mammillaria heyderi/maeiacantha (cactus retailers)
Echinocereus, most sp, where they fit. In Denver and wetter places, a slope or a rise help keep these drained.
Opuntia fragilis, small forms like the “potato cactus”
Coryphantha sulcata- delicious.
I know there are more small cacti. South Americans tend to want irrigation.
P. pachyphyllus
Penstemon
P. laricifoius, tiny, long-lived, hard to find. (Alplains, mailorder)
P. alamocensis, barbatus, - big plants with wee shadows (Plants of the SW, etc)
P. moffatii (nargs?)
P. pachyphyllus (alplains?)
I know there are many more...
Choice things/Crown jewels/hard to source/Oddballs
Astragalus spathulifolius (rare, seed)
Castilleja scabrida (rare, seed)
Penstemon acaulis- don’t you dare go pester this in nature.
Leptodactylon spp. (rare, seed)
Lepidium nanum (rare, seed)
Chaetopappa ericoides- good luck, witches.
Sphaeralcea caespitosa
Chaemachaenactus scaposa- long lived, hard to find seed.
Linum kingii- way cool.
Hoffmanseggia (Caesalpinia) repens.
Cymopteris bulbosus. Takes years, hates water.
Worth a shot, I haven’t tried them (enough).
Lewisia rediviva (NARGS)
Artemisia assoana.
Erigeron elegantulus (NARGS)
Penstemon linarioides. (NARGS, penstemon society?)
Stachys, fuzzy ones
Sideritis sp. (plant select...)
Salvia… most fuzzy asian ones will probably do, but most are too large
Pterocephalus spp. Not in GJ.
Petrophytum caespitosum of desert provenance.
Convolvulus boisseri, tragancanthos, etc.
Phlox ‘Lemhi Gem’
Achillea, miniature spp. like serbica, ageratifolia.
Penstemon petiolatus- perhaps on a north side as it happens in nature.
I have not trialled enough Grasses
Bouteloua hirsuta (Denver, not GJ?)
Bouteloua ‘Zig Zag’ very worth a shot in Denver. (Waterwise, High Country)
Lycurus pheoides (oh no, this one is good) (seed)
Muhlenbergia torryi, pungens. (seed from reveg folks in TX, etc)
Eremeoruruefurususus something. Fluffgrass. Annual or nearly so.
Aristida purpurea/longiseta. Often short lived and bad in dog fur. (seed)
Acnatherum hymenoides (1-2’ if you have space. Great. It’s been weedy for a rare few) (seed)
Hesperostipa comata- big translucent plant, no shadow.
Buffalograss can work as a “skirt” but will invade/cover rocks in a rainy summer.
I know, I know, there is ruby muhly at Apex, but there is ample space and it gets a little water.
Koeleria macrantha - someone should try it
Things you’d expect to go without water but won’t (usually)
Arenaria ‘Wallawa Mtn’ (it’s alpine and probably European, actually!)
Arenaria alfacariensis
Delosperma (with some exceptions… or they look bad when stressed. They need sun to be happy but need regular irrigation to be in sun…)
Thyme
Sedums (lanceolatum, and a few others allegedly have done it)
Sempervivum (also been a report or two but I am dubious. They are usually alpine plants)
Half the Mesembs/Aizoaceae/Iceplant family, generally. They just haven’t persisted without regular, if minimal, irrigation.
Erigeron scopulinus
Manfreda maculosa
Zauschneria (Epilobium), generally. I wish they did.
Coldhardycactus.com CO (Mailorder)
Ethicaldesert.com, CO Mail-order
High Country Gardens (mailorder)
Arrowhead Alpines (MI, mailorder)
Wrightman Alpines,(NB, Mailorder)
NARGS seed exchange (every Dec 15th)
Edelweiss Perennials, Canby, OR (mailorder)
Some of these are not pinned down for exact time or event yet.
Kenton’s Lectures 2022
Jan12:
Boulder City NV Garden club,
online 8pm MST
the Modern Crevice Garden
Feb 1-3:
ProGreen Denver, CO
Crevice garden construction for professionals
Sead Meadow panel discussion with Ross Shrigley and John Murgel
Feb 19: NARGS Rocks: Meadow Gardens conference, host.
Click to visit page and buy tickets!
March 16: Home Garden Club of Morristown, NJ? online?
March 19:
Watnog Chapter NARGS, 10:30 EST online:
the Modern Crevice Garden
April 13:
Evergreen Arboretum: 7pm online
the Modern Crevice Garden
April 4-8
Far Reaches Conservancy
Pt. Townsend, WA
Crevice garden annex build
Possible program TBD?
June 9
Plant Select, Denver
June 11th
Berkshire Chapter NARGS with Paul Spriggs
The Crevice Garden
June 20-24
APGA: Crevice Gardens
with Paul Spriggs and Jeremy Schmidt
Workshop/Build at Cistus Nursery
September 14-16
Urban Growth Conference, Malmö Sweden
Modern Crevice Gardens & Hardy Succulents
