Monday, January 12, 2015

Dirty Little Greenhouse Secrets

I wrote this a year ago when Imaginary Friends were planning greenhouses in 2014. These are the things experts do not tell you about hobby greenhouses.

Too much is never enough. When the last plant was tucked in last fall, He Who Mows said he thought I needed a bigger greenhouse. Perhaps I need to limit what I grow and bring inside.

I frequently look at Pins of Greenhouses online. Favorites of Pinners run to ancient ruins that could never be heated with obviously rotten window frames and tendrils of vines growing through gaps. Favorite accoutrements are chandeliers, upholstered chairs and tables with seating for eight. Rarely do the faves have an abundance of plants, mostly just a palm and some nice pots or even Bunny Mellon's famous greenhouse with all the trompe l'oeil. My tables for 8 are mostly for 8 pots of something.

Last year's Kalanchoes are now 14 inches high and budded. They graduated from here to  the back shelf of the potting bench for more light. 
They are so top-heavy they'll need cachepots to keep them upright.
(2015 note: I planted the Kalanchoes outside last summer and took cuttings, starting over in the fall.)

The primary components of a working greenhouse are damp and dirt. A dry greenhouse does not make for happy plants, so everything must be water resistant. In dry climates, some kind of mist system makes for very happy plants and helps with the tendency of a green house temperature to quickly rise to 30 degrees higher than the outside on a sunny day. Where the water from the mist settles determines placement of certain components, like a potting bench, painted items and electrical panels.

Dirt is a given. Potting soil does not stay in pots; transfer of potting medium from a bag to a container makes for dust and spills. Dead leaves and blossoms tend to fall or need removing. I can't sit and drink tea; I have to pinch dead blooms and sweep up.

I have not found it possible to store enough of daytime heat generated by the sun to keep the greenhouse warm all night, but ample thermal mass helps to mediate daytime heat and nighttime loss. Thermal mass in the form of water, concrete and brick must be carefully utilized. My water barrels support a broad shelf across the east end of the greenhouse. Sunny days mean a ventilating fan runs to try to keep temps down to 90 degrees. When we got back from Rose City this morning, it was 51º outside and the closed greenhouse was 81º -- quick, open the door!

Believing that every little bit helps, I fill 6-8 one-gallon jugs early afternoon that I use for watering the next day so they have time to absorb heat from the sun and give it up during the night. The floor is covered with a square path of concrete pavers with brick, urbanite and loose pebbles in the center, more mass and kind of decorative too.  You cannot have too many stones and brick. I have pots sitting around full of stones waiting for homes, absorbing heat in the meantime. If I can't have plant pots close together, they may be separated with a pot of stones or some other heat retaining mass.

Yeah, I do a lot of hand watering. Just directing a hose-end sprayer toward some pots doesn't work for me. I need to pull that plastic pot from its ceramic cache pot and check the heft of it, note if some mean bug has gotten on a plant and see if I need to do anything else after I make sure the plastic pot drained before I put it back in the cachepot so it doesn't sit in water.

Cachepots are not just for decoration, they help keep cheap plastic pots from falling over when foliage gets top-heavy and provide more thermal mass and a bit of space between the plastic pot and the outside one where little frogs can keep warm.

Heaters take space. I use two electric heaters turned to low. They need floor space where they don't blow directly on plants. During a warm spell they get moved away from the electric panel and back when it is cold again .

Seasons change. Pots that were prominent at Christmas lose their blossoms and need to move to make room for late winter plants in bloom, in turn replaced with spring seedlings. It's fruit basket turn over much of the time: making room for bulbs, moving some pots to the sun or in the shade.

Frog Poop, did I mention frog poop? It's everywhere in places like bromeliad leaves. Large commercial greenhouses spray for everything. I spritz around a little soap and olive oil sometimes for white fly but mostly I depend on critters' help. Little green peeper frogs are everywhere. One usually leaps on my head when I open the door at night or early morning. Green frogs leap out of cachepots when I pull out a pot to water.

I have to watch for toads making themselves a home in moist potting soil. Critical plants have to be up high, not at floor level if they haven't room for a toad. Anoles and eastern fence lizards roam freely. Insecticides are not on my agenda. Once you start, the critters are gone and spraying has to be kept up. Rare sick plants get tossed here. I discarded a diseased Amaryllis the other day. Things like scale get rubbing alcohol swabbing.

I've seen complaints about greenhouse mice. A greenhouse cat means no mice, but the cat has to have space. Ike the cat claims part of the potting bench, which needs to be cleared anyhow and a space back behind the potting bench that is a little shadier. I leave him a clear path to get where he thinks he must go and take care to block where he just wants to climb over plants chasing anoles.

I do make one exception: I use chemicals outside in the war against fire ants to keep them out of the greenhouse. I've become a little more benign against armadillos when they're digging into fire ant beds ahead of the chemicals.

The really odd thing in a greenhouse is that plants tend to grow. I'm always giving something a bigger pot. Pieces just will break off and I am not about to toss something that might take root, given a little pot and a bit of soil. What started as 6 different Schlumbergera were soon 24 at summer's end. It's like finding homes for puppies -- you want them to go, but to good homes.

Faced with an abundance of spider plants, begonias and foxtail fern at the beginning of fall, I jammed them in pots together.  Dozens of Alternanthera cuttings will fit into a coffee mug. Persian Shield and Purple Heart share a long planter. They'll be handy in spring when I need lots more purples and chartreuses outdoors.

Happy New Year. I hope you get a greenhouse, a big one.
If you have a greenhouse, I wish for you accoutrements.
Be prepared for dirt and damp but it isn't really work.


  1. I love this post. What it's really like having a green house. Yours sounds great. Wish I could visit. I'd never thought about people have the frogs and such. It is an ecosystem after all. Thank you for sharing.

  2. A great post! Thanks for sharing it again - got a chuckle thinking of you and the frogs jumping on your head. So many good things to remember, especially about the greenhouse getting too hot!

  3. Despite the challenges, it does sound like a lot of fun to putter about in your greenhouse. I would love to share space with some frogs, even if they occasionally landed on my head.

  4. I missed this one the first time around, so glad you re-printed it. Great advice! Happy 2015. P. x

  5. I don't have a greenhouse and doubt I ever will unless I move, which isn't in the cards. But I really really want one. Sigh.... I don't want a chandelier, either. Frogs and plants are so much better. :o)

  6. Great post, I now realise I do miss my greenhouse, must try and make room for one.

  7. One of the best posts I have come across, especially since I do not have a greenhouse but romanticize about having one. Bet it took some time to write this and compose it.

  8. A great reality check for all those romantic greenhouse pinners ;-) !

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  10. Thank you all for coming by. I hope I did not discourage anyone from any romantic notions. My greenhouse does have a 3-light fixture. I forgot the pic of it.

    I had friends once who installed a greenhouse next to their swimming pool. Naturally everything curled up and died as soon as hot weather arrived in Atlanta. Undaunted, she went to yard sales, bought pots of plastic greenery and flowers, decorated her greenhouse and closed the door. -- I left out the part about the flowers being faux in the previous comment.


I look forward to comments and questions and lively discussion of gardening and related ideas.

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