Hello! I live in Stow, MA and my container garden is located on a roof deck which is 20 feet above the ground. The deck is 24' x 11' - it gets bright sun and moderate wind. Temps here in the winter range from 50 degrees on a warm day to -10 F with low max -20 F. Windchills can be a bit lower. The weather oscillates between freezing and just-above-freezing temps every few weeks. My fair-weather plants that enjoy the sky garden in better weather, are now indoors (either in the sunroom or non-heated basement), or they are overwintering in a large pile of leaves in the forest. This is the first season I am going to attempt a winter garden on the deck. I have aquired several lovely zone 2-4 hardy plants and my intention is to keep them alive on the deck throughout the winter and likely living in pots for 1-2 more years before being planted in the earth. Their uninsulated pot sizes range from 4" to 14". They include: Shrubs: Red Sprite Winterberry, Pyracantha Mohave; Small Plants: Boulevard Cypress, Gold Threadleaf Cypress, Blue Star Juniper, True Dwarf Norway Spruce; Young Trees (3-6'): Pine Japanese White, Pine Eastern White, Pine Blue Spruce.
I've been told 2 different opinions on the care of the blue spruces, norway spruce, juniper, and cypress plants: 1 garden professional tells me they will not need any insulation "they are zone 2 hardy", the other professional tells me I should insulate all of the plants to minimize the freeze/thaw oscillation that will eventually break down the roots - for example - the tiny dwarf norway spruce - now in a 4" containter - "should have a ball of insulation around the roots that is approx 2-3 feet in diameter". Regarding the japanese white pine, the winterberry and pyracantha, the professional tells me I should plant these in the ground "for the guarantee" - I would like to keep these as part of my sky garden, 20 feet above the ground. How can I best insulate them to ensure their survival?
Right now, I have built around the bare pots (roots with soil in a thin plastic pot) the following types of insulation:
1. Japanese white pine (bare pot = 9" diameter) - 3 pot approach: bare pot set inside a 1" thick double wall plastic pot, with straw mulch as insulator (5" below root base, 2" on sides) - this set inside a 2" thick, 21" diameter foam insulated pot with straw mulch insulator (3" below pot base, 2" between pots) .
2. Dwarf Norway Spruce (bare pot = 4" diameter) - 2 pot approach with lots of insulation on all sides: bare pot set inside a 12" diameter foam insulated pot with straw mulch insulation (4" below root base, 4" on all sides).
3. Pyracantha (bare pot = 9" diameter) - 2 pot approach with less insulation on all sides: bare pot set inside a 11.5" x 11.5" square tin container with straw mulch insulation (6" below root base, 1" on sides)
4. Blue Spruce (bare pot = 14" diameter) - 2 pot approach with less insulation on all sides: bare pot set inside a 18" diameter 1-layer plastic pot with foam pellets, peat moss, straw mulch insulation (4" below root base, 2" around sides)
Hunches/Questions
Is there some type of solar blanket insulation for these less hardy - or perhaps all - of my sky garden plants? I'd like to maximize the plentiful sunlight energy I get on the roof deck and direct it towards the stablization of the insulation/soil temps within each pot to minimize freeze/thaw root breakdown.
I'm thinking I should probably put a cloak of plastic over the top of each container and tie it at the base of each plant to keep out the rain and snow which will ruin the dry insulation I have right now.
I'm wondering about the advantages of putting a layer of water heater insulation or other type of building insulation (with holes drilled into the bottom for drainage?) beneath/around each pot...
Thoughts? Lessons learned from previous winter sky garden experiments? Thanks!
Mary
Winter sky garden experiment
Nobody answered this, so let me put in my 2c worth... the leaf dessication is something you havent mentioned and it could be a very big deal. The pyracantha will be affected the worst, with the spruces following. The tips of each needle on the southside might bleach out if you have a full winter...frozen everything with full sun. Not sure on the white pine. Wilt Pruf will maybe take care of the dessication. The plastic will not be good, I don't think. I was kind of thinking rain and snow would be good for them. You could use fabric remnants, but then what's the point of a winter garden if it looks bad?
The other thing you haven't mentioned is the plants being rocked by wind which has the same consequences as freezing and thawing, but if it happens when the soil is frozen, you could get very badly ripped roots or the whole plant uprooted. The blue spruce because it is so full and thick will be the worst affected because the wind doesn't sort of rush through it. Make sense?
Insulating pots - use straw or potting soil. Just get some big foam pots from a discount big box store -- and drill some holes in the bottom if they don't have them. Fill them with sand, potting soil, rocks, whatever is cheap and easy. I might look into shredded hardwood bark mulch because I think it looks good, but sand or rocks are nice because they're so heavy. Straw is good in theory, but it looks like hell and will trash up the place and really doesn't weigh enough to hold those pots down and keep them from flying. It's ok if the insulating agent gets wet. Freeze dried coffee and freezer burn and what I see here make me think freezing actually dries things out. Not ponds, but soil.
Some advice: stay away from styrofoam peanuts unless you want to waste time picking them up when they spill. Your pots could fall over, be pushed over by vandals, or you could forget the peanuts are in there and tip them over to transplant. Somehow, at least at my place, they always end up on the ground for me to pick up. One time I got them in a garbage bag and out to the street and dang if the trash guy didn't snag the plastic garbage bag on part of his truck and sliced it open. He drove off and I picked up the peanuts from the middle of the street. This is of course, if I don't dump them myself.
Hope this helps,
Suzy
Suzy: Thanks so much for your reply! Yes, The garden professional did make me buy the wilt pruf and suggested I apply it once now, and once again in Feb. I hadn't thought about the wind... You make an excellent point. Luckily, I am a bit sheltered by bigger trees around the building I'm in...that should cut down on some of the windiness. The trees also have the deck railing for support/fly away guard, which will cut down on tip-overs. Thanks for the advice re: styrofoam peanuts. I'll stick to the foam pots and straw.. maybe I'll pick up some bark mulch.
Thank you very much for your insight,
Mary
I'm not sure if I can add much. I've never had a project like this but I really like the idea and would love to see some pictures. I was wondering if you would put your individual pots together in groups and use large Styrofoam boxes to hold them. Put several pots in each box and put wood chip mulch under and around the pots. It could be attractive and the mulch could be reused in the spring. You can buy Styrofoam sheets and cut them to the desired size and shape. They can be painted and you can even add dimension and embellishments. You’d be surprised how nice they can look. Holly
Mary...well...what's been done is done already I imagine.. I've a few questions and a few comments and an account of what I've found here.. I too have a roof I garden on.. I was raised just south of you there... Iwas in in Southborough..it does get cold there..
Questions..
you said you were on a roof deck.. now does that mean you are on a roof top.. on a deck on the roof.. or you have a deck above the roof.. or you have a deck at the height of your roof...all real important to me..
What's with the straw.. it's between your pots and the outer pots ...why..straw..when it gets wet it has zero insulation value..well some what aproaching zero anyway..
the nurseryman was right in sayng your biggest problem maker is the warm winter sun hitting the plants/pots and warming them up in the late afternoon..thawing the plants and planters.. getting the fluids flowing.. then a hard freeze in the night .. freezing the moisture.. which expands when frozen..and ruptures the capalliarys the water is in..turning the plant material to mush.. if you are on a roof it's self ..like on tar or rubber... this will give you the most warmth here.. if there is a deck.. like wooden 2 x's.. or the 5/4 decking... spaces in between the deck boards.. to bleed of heat that will be some insulation from the roof it's self... ..see the root balls are about out in the air.. in the planters.. the roots will be about the air teps adveraged over time..day/night /warm day cold day.. the soil has an eaualizing nature..solar mass.. USDA zones only consider winter low..AIR temperatures..and they are thinking for a given zone the ground freezes to a certain depth.. I forget what it is there in Mass... below that the water in the plant roots is liquid all year long...likea big pine will have 100's of gallons of liquid..flowing day and night all year long.. below the freeze line...now their water is in the sap...which raises the freexing temperature..as it will freeze at a lower temp than water alone.. so with your plants up in the air...always below freezing... it could lower your zone appreciably.. plants planted in the ground... have the entire solar mass of the earth to warm them... below the freezing line in the soil..you'll get none of this with them in the air.. that's why they winter mulch... to keep the heat in.. and raise the freeze line.. mulching these things all in the air... will do little more than make your pots prettyer..but they will keep the sun off the soil.. and keep them colder.. and help them from warming up.. like reverse of how it works on the ground..but that's good.. as the warming is the killer here remember..
ok... I use 1"" to 2"buildersfoam..on the outside or the inside of many pots/planters.. that aren't already made of solid foam..[ the best ] I use broken up styrofoam in the soil to help with drainage.. a frozen drain hole is like a basin of water.. all water ..no air..[ suffication ] you want to keep the drain holes open..summer or winter.. keep everything frozen till it is really spring.. keep the sun off the deck...the pots.. and the trunks of the trees.. if possible.. and have the biggest root ball you can to keep up the mass of the unit.. keeping it cold and taking longer to thaw out..
keeping this mind set in whatever you use..will help them survive..
now me.. I have planters on the rubber membrainne it's self... some are above it if possible.. In the summer if it's 80*F in the air.. the roof deck is at 145*F..by measurement here.. the same goes for the winter.. but not as high... it canstill be 30-50*above the air temperature... foam in the bottom of thte pots helps this also.. I like the chunkey broken up styrofoam.. which the roots will actually grow into and through.. seeking watertrapped in the fizzzures of the foam.. this anchors the roots to the soil.. like nothing else will... preventing movement by the wind... I have a fewJapaneese Maples.. holly.. eueonomeous.. hostas..a vaigated pine..called dragons eye.. roses.. cypress.. and a hoast of others.. well into their second decade ...give it some thought... and keep them cold... till spring...
I do get alot of squrels planting their nuts in my planters.. they know they will thaw out weeks before they can get their nuts out of the frozen ground... for that late winter meal.. they climb the 60' up the fire escape to do this... with the nuts they give them in the park... as peanuts aren't found growing about the city here..I get a few pounds outof the planters every spring as I refomulate and fluff up the planter dirt.. in the empty planters..for annuals and veggies..
best of luck with it all... Gordon
This message was edited Dec 30, 2006 11:55 PM