greenhouse layout advice pls

[Gadus]

I've just had a 25 X 30 pad leveled for a greenhouse site. My father is not currently using his 12 X 20 storage shed so I'm going to try and grow things in it. I'm going to buy some 4 yr, 6-mil plastic and anchor the greenhouse to a base of railroad ties.

I'd like some help with the layout... Given that the shed sides are sloped not all of the width is useable space so I was tentatively thinking one or two central beds might make sense, with plenty of room on the sides to walk around. Say, 4 X 16 or two beds, 4 X 8. I don't want to be cramped working but at the same time, don't want to waste space.

I also wanted to leave adequate room for a bench/table for seedlings, tools, etc.

I plan also to elevate the bed/s to a comfortable height for everyone in the family to be able to plant/harvest comfortably and to do so I'm going to need to provide a base layer of soil 2-3 feet deep. I was thinking just to bring in some gravel and cover it with landscaping cloth and then fill in the last foot or so with the good stuff. Does this seem like a sound idea?

thanks

[HoneyBerry]

Myself, I don't like hauling gravel, so I would find another way to elevate the beds. 12" of dirt might not be deep enough for some plants. I'm thinking about doing something similar as what you are doing with my old wood shed. If I run across any good ideas, I will pass them on.

[Allyn]

Instead of building beds on the ground and then filling the bottom couple of feet with "filler," could you use tabletop beds instead? Something along these lines:

(Image by Dan Malec)

The bottom shelf can be a second tier of plants or it can be storage. You'll need places to keep bags of peat moss and compost, et al as well as bottles of plant food, tools...

[Gadus]

Maybe that's the sensible route to go, given the space. However lumber is not cheap. What would you recommend, in terms of planters for a greenhouse of my size (12 X 20')

How is a second tier of plants able to get adequate light?

How deep of a bed is required for peppers, eggplant, tomatoes, other hot plants?

Thanks.

[applestar]

When you create raised beds, the best dimension is a width such that the gardener can reach to the middle from both sides without stepping inside, and across the entire bed when access is limited to only one side.

Here is a construction idea I tried that may work for you:
Subject: Pallet sided high raised bed hugelkultur experiment

Note that I filled the bottom with branches in a sort of hugelkultur style, though I didn't have the materials to create fully hugelkultur mounded bed.

Also check out rairdog's thread: Subject: My first year raised bed with hugelkutur

Generally speaking, if there is no reason to limit your plant roots' access to the ground below, its best not to use underlayment such as landscape fabric and gravel. (Some reasons include contaminated ground, soilborne pests such as root nematodes and voles, and tree roots.) Plant roots grow to depths of FEET.

However, for a gardener in a wheelchair, it would make sense to build a wheelchair accessible table bed that can grow shallower-rooted plants. Plants can and WILL compensate for shallow depth by growing and spreading their roots sideways. This means they will compete more with each other for water and nutrients.