If you live in a condo so it's worth the investment to install a real green-roof gardening system, go for it. But if you're in an apartment, that changes the equation a bit. I came up with this system to give my terrace the look and feel of a green-roof perimeter, but still keep the cost and hassle manageable. I thought I had posted this a long time ago, but when I went back through all 3 posts I have added since I made this container garden, it wasn't among them. It goes like this:
Shopping list includes potting soil, gravel, plants, and concrete mixing tubs. A drill with a large bit is helpful. If you don't have a drill, you might be able to make holes with a biggass nail and a hammer, but these pans are pretty rugged for plastic. The medium tub at Home Depot is a good size for this project, but use whatever size works for your space.
http://www.homedepot.com/h_d1/N-5yc1v/R-202086173/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053
 |
| Medium Concrete Mixing Tub |
Drill at least one hole into the end of the tub, about 1-2 inches up from the bottom. I made 4 in mine, but that might be overkill. This will allow excess water to drain, but also gives it a reservoir that will reduce the amount of watering you will have to do.
Pour about 1-2 inches of gravel into the bottom of the pan. I used Home Depot's 40 pound bags of pea gravel. One bag will be enough for 3 or 4 tubs.
Spread some of the potting soil over the gravel, and then arrange your plants in the tub. Pack more soil around the plants and water generously.
 |
| These succulents are all hardy to -20 F degrees and need very infrequent watering. |
Because these pans are shallow, and because you are a seriously urban apartment dweller who has better things to do than water the garden daily, I highly recommend sticking to plants that have a very low water requirement. Also, if you want them to grow back in the spring, they need to be very cold-tolerant, since it is a pretty good bet that the soil and roots will freeze solid at least a few times over the winter. In general this will mean those of the variety known as succulents. There is a huge variety of plants that will meet these criteria. I went for having lots of variety, but I could also envision picking out just one and going for a monoculture. (If you do that, look for one that says it will grow quickly so you don't have to haul home as many plants.) I can get by with watering these "green-roof" plants once a week (if it doesn't rain), although I water the non-succulent plants every other day, and daily when the heat is really brutal.
 |
| More drought and cold tolerant succulents. |
Here are some of the pictures I took while I was putting them together, plus a few that show how nicely the plants grew and filled out the containers. About 85% of what I planted Year 1 came back even more robustly in Year 2, and I could fill in the holes by splitting and transplanting the ones that made the cut for "survival of the fittest".
 |
Mixing pan, pea gravel,
soil, and plants. |
 |
That spot on the leftish side
shows the position for one
of the 4 drainage holes I
drilled with a 3/4" drill bit. |
 |
Spread 1-2 inches of gravel.
This allows for drainage from the soil
and creates a reservoir for water. |
 |
| Spread some soil over the gravel, arrange the plants in the container and fill with more soil around the plants. I started out with about 6 one-quart plants per container. |
 |
| By the end of the summer all the containers were overflowing, and in the second year I could split them and transplant them into other containers. |
 |
| One of my green-roof containers in between some other larger planters |
 |
Some succulents have a nice flower, but most are various
shades of yellow, green, or red foliage. |
 |
| The one on the right has plants my cats like to nibble. |
 |
| Cat grass from PetSmart is in the back corner, |
