Even if you're a seasoned green thumb on the ground, you'll find that a balcony or rooftop garden presents different challenges:

Size and scale: Although your garden space may be small, it doesn't mean you should stick to small plants. Scott Endres, owner of Tangletown Gardens, suggests bigger, bolder plants that can hold their own, especially if you live downtown with big buildings, urban noise and the river. "Choose things that can compete with the scale of the surroundings," he said.

Toughen up: Your favorite garden flower may not be sturdy enough for the growing conditions on a balcony, which are often windy and hot. Endres suggests plants with tougher, fleshier leaves, such as mother-in-law tongue and succulents. Plants with big loose leaves, such as banana trees, will likely get shredded by wind. "That big leaf is like a big sail," he said. "You can still create drama and effect. Canna has big leaves, but closer to the stem."

Don't skimp on soil: Plants have less soil in containers than in the ground, which is why the character of the soil is more important. "Get good quality potting soil, the highest you can afford," said Paige Pelini, co-owner of Mother Earth Gardens. "The plants will need every bit of nutrients available to them." And plants that aren't nourished properly are more susceptible to outside stresses, Endres said. Soil that contains water-holding polymers can help plants weather the hot, dry conditions on many balconies.

Growing edibles: If you want to grow tomatoes on a balcony, they'll need lots of water and attention. "Tomatoes can do well in the right container," said Pelini. "But the drawback is they have to be watered daily." If you're heading out of town, even for just a weekend, you need to make arrangements for your tomatoes, or you'll return to dead plants. "Either set up a drip irrigation system or have somebody come water your plants." Peppers and eggplants are a little more forgiving of inconsistent watering.

When choosing containers for vegetables, get the biggest ones you can fit in your space. "You'll get more consistent temperature and more room for roots," Pelini said. Herbs, such as basil and mint, are also good balcony crops. They're easy to grow, expensive to buy at the grocery store, and they come in handy for summer favorites that will impress your guests, such as mixing up a mojito or a batch of homemade pesto.

Kim Palmer