A few years ago, I successfully winter sowed some penstemon, California poppies, and columbines by sprinkling the seed on potting soil in clay pots, and then covering the seed with a layer of fine gravel. I prepared the pots in late December and then put them outside on our front porch, up next to the short brick wall on the east side of the porch. They got a good dose of morning sun every day (Denver has lots of sunshine, even in winter), and when it snowed, they ended up with anywhere from a light dusting of snow to a few inches of snow that melted off in a couple of days. I didn't cover the pots with anything to help hold in moisture and only watered them two or three times if they were starting to look particularly dry.
Has anyone else ever tried this method of winter sowing, and if yes, was it successful? I've been away from gardening for a couple of years now but getting back into it again and am particularly looking forward to trying the clay pots with gravel again this winter to see if will work again. I'm also considering trying some of the other types of containers (e.g., milk jugs and whatever else I can lay my hands on) that will provide a bit more of a greenhouse effect and will put them in the same semi-sheltered location on the front porch. Because it is not as open to the elements as just plunking everything in the backyard, I'm sure I'll have to provide a drink now and then, especially if we have another dry Denver winter. I'm kind of concerned about being too zealous with the watering though. How dry do you all usually let things get in your containers, especially before the seed has germinated?
I remember reading (think it was on Trudi Davidoff's site) that the way to tell if your WS-potting mixture was too dry was if it looked light-brown. Otherwise the potting mix should look "like a brownie," e.g., dark brown, and moist but not soggy. This is how I judge my milk-jugs, which usually don't need much if any supplemental water until I've removed the tops in late spring. Then I can easily observe the soil drying out. The beauty of the closed tops is that they trap moisture inside and you don't really have to water them much --you can see the drops running down the sides whenever the temps warm up a bit.
I've never tried the idea of topping up open the pots with gravel. Sounds like you're creating a mulch over the seeds, which Mother Nature also does naturally with dirt and then snow in regular flower beds. I can see how this would keep birds from making off with the seeds, as well as protect them from wind & water runoff. And the seeds you sowed were pretty hardy ones that perhaps didn't need the temporizing effects of a protective "greenhouse" cover as much as other more tender plants would.
I think you should try both methods this winter and see which you prefer! And report back to us here on the WS forum!
CapeCodGardener wrote:I think you should try both methods this winter and see which you prefer! And report back to us here on the WS forum!
I think that's what I'll do, if I can gather enough empty milk jugs and pop bottles. I've already got my seeds ordered to experiment with, so it should be interesting to see if there's any significant difference in the germination rate for each type of seed using both methods.
I tried seeding into pots with a plastic colander as cover to keep critters off.
My results were not as good as the milk jugs.
The colanders cut down the light and allowed moisture to evaporate.
Covering with sand is okay for seeds which do not need light.
I sometimes seed small seeds onto a layer of sand,
as the sand keeps them in place and they don't wash to the sides.
Just looked at a video this morning on a well known garden center in northern Va. area where the horticulturist has a tuitorial on how to make a container planting. She showed using about a 6 in. square piece of landscape fabric over the drainage hole to keep the soil from going out the drainage hole, then she added about 1 inch of pea gravel over that, then her potting mix, fertilizer(Osmacote) and she showed others(Flower tone) and she suggested added more of the pea gravel on top of the soil because squirrels and chipmunks like to dig in fresh soil and the pea gravel helps keep the moisure in. She also put the pea gravel in the container saucer so the pot wouldn't be sitting in water, and pot feet. Check Merrifield Gardens website. Watch her video on container gardening if you are interested. I love tuitorials. I find them very helpful and informative.
With this pea gravel on top of the container, would seeds be able to penetrate through all that gravel and germinate? What about using that same soil the next year in your container; what do you have to do, pick each piece of pea gravel out or just mix it on in with the potting mix afterwards?
I use large 14 inch and 20 inch pots so they would be heavy with gravel.
I use vermiculite or perlite in the bottom. Some plants like a gritty layer on top.
Iceland poppies and alpines like gritty material.