A little late in the year.

[cyberdan]

I just finished a greenhouse. I know it is late in the year but we had other projects that needed to be done first. We built new just over a year ago.

One at the top of the list was get rid of gophers. Have not seen a new mound in a month.

So here is my question for the new 10 x 11 greenhouse. I leveled the ground as best as I could and then put down a weed barrier from Home Depot. (black porous plastic on a roll 3' X 50') then put the frame on top of that. (I don't want to have to mow the grass in the greenhouse.

What do you put on the floor? I could buy a yard of pea gravel or sand but that might be too much. The local garden supply has red mulch 2CF at $3.33 each. Do you think it would be wise to use mulch? I know it has a lot of moisture in it and will eventually dry out. Would that cause mold problems?

It never gets hot here 62 - 65* is about normal. 70* is a heat wave.

Thanks, Dan in very northern California coast.

[Nan_PA_6b]

Dan, are you going to be growing in-ground in the greenhouse?

[cyberdan]

No my wife want containers only. nothing on the ground

[bower]

I think one advantage of gravel or sand is a non slip surface. And of course it will allow water to percolate down below instead of pooling inside the greenhouse. A third reason is for the heating/cooling economy of the greenhouse.

In a cool climate where you may want to close the greenhouse from time to time, to keep your plants warm, you don't want any standing water, puddles or pools which vaporize as it gets warmer and then as it cools, ultimately condense on plants and other surfaces and create a habitat for mold. You may also get algae and/or mold growing on top of the plastic mulch due to water always spilling down on it. Sand doesn't drain as well as gravel IMO...

Gravel is also a decent heat storage mass. Any storage mass inside your greenhouse will take up heat when it's hot and release heat when it's cold, and help to moderate your greenhouse temperatures. Sand is not as good (I think?) for that purpose... but second best. Plastic mulch? I think would have a negative effect on the heat economy, reducing absorption of heat also by the ground below, as an insulative barrier to heat transfer.

So I would go for gravel, personally. Even a thin layer half inch or so would be a positive contribution to your overall heating/cooling economy and non slip is a bonus in my boots. I would definitely slip on wet plastic mulch. And I would end up tracking wet sand all over the world/garden/house so that wouldn't suit my boots either.

[ContainerTed]

Also, red mulch is not a stable color. It will bleed onto your shoes and become a hassle back at the house. I agree with the comments about gravel. The usual components will easily store heat and release it at lower temps. It will also keep the containers off of flat bottoming out and allow the pots/buckets/etc to drain more efficiently. I also agree on allowing the water to pass thru the floor quickly to lower the risk of any mold or fungus developing. If your base is not easily absorbing the liquid, like when the base is clay or caliche, allow drainage from a not so perfectly level base to move the water out of the greenhouse footprint. This will allow you to control the humidity/wetness inside the greenhouse with better results.

[Sherry_AK]

I have bricks on the walking areas and gravel where the containers are placed. I like it because the brick holds the heat, or I can spray it with cold water if I need to cool things down a bit. It's also easy to sweep the brick areas to keep things tidy. I'm very pleased with this arrangement. I would not use mulch.

[b54red]

I started with gravel but with all the heavy rain here and very warm weather I had things springing up everywhere. I was constantly pulling weeds or the results of spilled seeds. I also had the problem of the potting medium getting in the gravel and eventually it looked just like a dirt floor and acted like one. I ended up putting down a thin layer of concrete and tried to sloop it so everything drained out one corner. It did make it a lot more user friendly since I only grow in containers and it is so much easier to clean up all that spilled potting mix that I can't seem to keep in the containers.

Bill

[KarenO]

My hobby greenhouse floor is natural shredded cedar bark mulch over two layers of weed barrier fabric.. (Don’t use dyed stuff it’s full of chemicals)
I find it insulating and helps me heat my greenhouse in spring. Cold wet gravel makes it hard to warm it as it just sucks the heat right out. You can always easily rake it out, add more etc. it’s nice to walk on, packs down firmly so shoes stay clean smells great too.
KO

[cyberdan]

Thanks all. I am on my way now to go order a yard of gravel. Most of you recommended gravel and that was in the back of my mind too. Only need .75 yard so I need to figure out what to do with the extra.