Cold greenhouse growing thoughts & ideas for zone 8b?

[bibliofloris]

Hello!

I'm new to this forum (apologies if I'm posting this in the wrong spot!), and I'm just coming back to growing tiny treasures after a busy few years focused on other life areas, so I was very glad to find you.

I have a lot of work to do to get my garden back in shape (and most of it isn't the fun parts, sigh). But, to treat myself, I've bought a cheap polycarbonate greenhouse kit, and am planning to set it up as a (very small) cold greenhouse.

I expect to have it put together by the end of the summer, in between other projects (and work and all that), so I have a couple of months to figure out what to grow in it. I'd love to hear what you suggest, and any thoughts or tips you have. (I've used cold frames, but never had a greenhouse before.)

I live near Seattle, in Washington state, USA, US zone 8b. Minimum winter temperatures can get as low as 10 degrees F (-12 degrees C), but usually for only a night or two; 25 to 40 degrees F (-4 to 5 degrees C) is more typical for the cold part of winter. Summers tend to be cool and dry (it's about 60 degrees F / 15 degrees C here today, in June.) I believe the latitude is similar to Paris, and day length is an issue November through February.

Here's what I've been thinking about so far:

I love growing tiny treasures, and they get lost in my garden (or gobbled up by slugs or chickens.) I'd love to have pots of small hardy bulbs and perennials bloom in a cold greenhouse in fall, winter, and spring. Maybe cyclamen species, galanthus, and small species fritillaries, narcissus, and tulips? And some small primulas? I have Cyclamen hederifolium, coum, purpurascens, & graecum (the graecum is currently inside my house), some auriculas, and various small bulbs. I love slightly peculiar flowers more than pretty ones, so I tend to collect things like Arisarum proboscideum and Galanthus 'Blewbury Tart' -- and they'd be much more fun to visit if I didn't have to crouch down in a cold, wet garden!

I'd love to have a spot to overwinter dormant potted plants that are borderline tender here -- I have a few eucomis, for instance, and I'm looking for Begonia sutherlandii again. Has anyone tried a cold frame or styrofoam box inside their cold greenhouse for the really cold days, for things like that? Any better ideas? I know I could use a heater on a thermostat, but it seems a little silly to heat a whole greenhouse just for a few dormant pots. Though I'm tempted to try some begonia cuttings too...but I think I'd better have backup cuttings inside my house for those, and consider them an experiment. (I can grow things inside, but all the good spaces are already full of orchids.)

I'd love to try some lachenalia, but I'm worried they'll get too cold in a cold greenhouse, and too warm/dry in my house. Has anyone tried growing them in a cold greenhouse and bringing them into a cold room inside for the days/nights when it's below freezing outside? Or a heat mat in a cold greenhouse?

I love growing things from seed, so it will be nice to have a slightly protected environment for seedlings like cyclamen and primulas.

Most of my backyard is shaded April through November by huge maples (Acer macrophyllum) -- including the best spot for a greenhouse. So, I think I'll probably move anything that wants sun outside for the summer, give the greenhouse a good clean, and use it to repot my houseplants and give them a little bit of almost-outdoor living in summer.

Given these conditions, anything you'd suggest I grow? Anything seem like a really bad idea? Thanks in advance!
Kelly

PS Sorry for the long first post -- dreaming it all up is the fun part!

[brianw]

Hi Kelly. Welcome. If you like peculiar flowers, especially if they are usually white and green, you could not be in a better place.

Here in the southern UK temps. as low as yours occur, but only rarely. I over winter "ordinary" Eucomis outside in pots against the side of the garage just covered with a "tarp" so they are dry, but most are planted out in the garden. But winter growers like Lachenalia are different and I keep them in a frost free (nominally 6C min). I think you will need to protect them in some way that is practical to you, either with a mini greenhouse on the floor inside your other, or take them into a frost free place when threatened. Some lachenalia flower earlier than others. Maybe stick to those and accept they will get their leaves frosted of at the end of their growing season, then put the bulbs somewhere frost free.
My problem this year is it is just too hot and my losses will be quite high. The shading in just not enough. Now they are threatening restricting water supplies and my rainwater storage is getting low.

[Maggi Young]

Hello Kelly, welcome to the forum as well as to SRGC membership!

Sounds like you have lots of  fun ( and work!) to come.  I'd say that the best way to find what might work in your conditions is to  grow lots from seed and  discover that way what likes to grow there.
 The use of styrofoam boxes  to house  more tender plants in very cold weather is  done quite often - and the use of the lid of such boxes  can be added  for the worst times, with perhaps  just a layer of horticultural fleece  for  milder spells so you are on the right lines there.

It'll be great to keep up with your progress and experience with this project. Wishing you lots of  happiness from it!

Maggi 

[bibliofloris]

brianw, thanks for your thoughts on the eucomis and lachenalia. L. viridiflora is my favorite, and luckily it’s an early bloomer, so perhaps I’ll start there.

Maggi, thanks for the info about styrofoam boxes - I’ve never seen them used here, but I couldn’t see why it wouldn’t work? Glad to hear it’s already been tested! And yes, I’m looking forward to starting lots of seeds!

Thank you both for the warm welcome!
Kelly

[Diane Whitehead]

It's important to keep bulbs in pots from freezing.  I lost many pots of South African bulbs that were
up on a bench in a small greenhouse on an unusually cold night.  Potted plants outside on the ground
survived - I guess the soil has residual heat.

A few ways to protect your pots:  sink them into a sand bench, cram them into styrofoam boxes, huddle them together
on the ground.

I was impressed with the sand-filled benches at Lohbrunner's alpine nursery.  They were filled with small
clay pots of plants, and when one was removed, an empty pot was immediately popped in to maintain
the hole.  So organized!

[bibliofloris]

Good point, Diane — I hadn’t thought about them not being in contact with the ground. Sand does seem helpful that way, if I build something that supports the weight.

Thanks!
Kelly