To celebrate my 5th gardening (and blogging) anniversary I've compiled a list of tips I wish someone told me before I started growing food on a rooftop.
Never ever let your containers dry out.
Water stressed plants are more vulnerable to disease and pests and produce lower yields than their healthy counterparts. Do not underestimate how quickly a container can dry out on a roof. If you think a container will dry out before you're available water it again use soda bottle drip irrigation to make it through the day.
Move plants around.
Every gardening space has several micro climates. If a plant is not doing well in one location move it around till you find a sweet spot. As the weather gets warmer move the plants so that they're shaded during the hottest part of the day. During the height of summer, when you can fry an egg on your roof, raise the pots off the roof surface to reduce the heat that passes from the roof to the pots.
Wind and sun, but especially the wind, will quickly suck the moisture out of soil. Covering the soil with mulch will help it to retain moisture, as well as block weeds from growing in the container. I prefer to use white plastic as mulch because it also helps to keep plants cool in the summer.
Support your plants with a stake, cage or trellis
Branches heavy with fruit can easily snap in high winds, tie them down before a wind gust gets them. Also, don't give the wind the opportunity to snap your young transplants, add the support at the same time you place your plant in the container. The only plants that don't require support are root vegetables and leafy greens.
Plant varieties that produce small or medium sized fruits
The larger the fruit size, the greater the water demand, demand your container might not be able to meet as the fruits grow larger. "Dwarf" or "container friendly" varieties are a safe choice. Check out my favorite seeds for rooftop vegetable gardening for some recommendations.
Don't rush your plants outside
Average last frost date is just a guideline, not an absolute green light to plant every seedling you have outside. Listen to what the weather is telling you and pay attention to soil tempurature, if it's too cold for the plants they'll just sit there and sulk until it warms up. You can even permanently stunt the growth of certain vegetable varieties if you put them out too early. Play it safe and wait a week or two.
Learn from others
Follow garden blogs that grow in similar conditions to your own garden. It's very likely that they will experience problems and situations that you will encounter, as well as offer relevant growing tips and solutions.
You'll make a lot of mistakes when you first start out. This is completely normal, don't let the fear of failure prevent you from experimenting.
Beginning gardeners tend to spend too much money on supplies and unnecessary gadgets to compensate for inexperience. This doesn't work. Plus, if you find out gardening isn't for you, you've just wasted bunch of money. Ease into gardening, you'll save yourself a lot heartache.
That's all I can think of right now, what would you add to this list?