Q: Now that we’re basically frost-free, I’m eager to start growing some of my own food. All I have is a balcony, though, so what are my options?
A: You can get pretty creative with container types and planter arrangements to try to make the most of the horizontal and vertical space (though be mindful of load limits for structural safety). The most limiting factor in plant choice will be how much direct sunlight the space receives during the summer. Full sun, the ideal exposure for most edible plants to maintain good health and productivity, is a minimum of 6 hours per day (continuous or cumulative). Some plants will tolerate less, but may produce a reduced yield or will grow floppier and less compact.
The second limiting factor will be container volume, with larger pots being more insulating, less prone to rapid drying and more accomodating for root growth. Make sure containers drain well – don’t block drain holes or fill the pot’s base with stones or pot shards – and if you need a saucer to shield a downstairs neighbor from drips, make sure it gets emptied after each watering or rain. Otherwise, that pooled water can soak back into the soil and drown roots (or breed mosquitoes). If drips aren’t an issue, just skip the saucer.
Herbs are relatively easy, especially if the soil tends to dry out quickly. Not all survive the winter, but several can. For vegetables, leafy greens can also work well, and lettuce doesn’t mind the cooling benefits of some afternoon shade. Small bush-type cucumber varieties won’t sprawl nearly as much as typical cucumbers, though their melon kin are too space-hogging unless you have an expansive deck.
Compact varieties of tomatoes, peppers and eggplant, plus summer squash, lemongrass, and other warm-season crops benefit from a minimum container size of about five gallons per plant. A hardware store bucket with holes drilled for drainage can work quite satisfactorily if you don’t want to spend much on the container. Winter squash and full-size varieties of the above need closer to ten gallons of soil volume per plant. You can explore more tips for container size on our Types of Containers for Growing Vegetables page.
For fruits, you can try strawberries, but use day-neutral varieties for the fewest runners and a longer harvest season. Compact blueberry cultivars and dwarf brambles (blackberry, raspberry) have become available in recent years and are ideal for container culture. Lowbush blueberries, the “wild blueberry” of recipes, is naturally compact and might also give you enough for some breakfast garnishes or a batch or two of muffins. Cross-pollination between different cultivars improves berry production for blueberries, but isn’t necessary with brambles or strawberries.
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Tree fruits can be challenging to cultivate in containers, and balcony space is usually too limiting. There are a few genetic-dwarf varieties which stay smaller than varieties dwarfed by grafting, such as certain peaches and apples, but root spread limited by a container may restrain their growth even more. Plus, their upkeep to prevent pests and diseases from injuring the tree or ruining a crop may prove to be not worth the effort when space is at a premium. You could grow tropical fruits like citrus instead, but they’ll need to come inside for the winter.
Q: Some of the vegetable and flower seeds I’ve sown haven’t come up yet. What might be the reasons why?
A: There’s a few potential reasons, and the most likely factors will depend on the type of seed. Planting depth is important, because while some seeds need darkness as their germination trigger, others need to receive light from being close to the soil surface. If you seed, the packet or catalog should tell you the ideal purchased planting depth.
Consistency of soil moisture also has an impact, not only so the seed can absorb moisture through the seed coat, but also because emerging roots (which appear before foliage) are very vulnerable to desiccation. Drying too much from uneven watering will interrupt germination and can kill a seedling, which is why newly-seeded lawns are watered so often, for example.
Soil temperature influences germination, with warmth speeding the process. Indoors, try using a horticultural heating mat under the pots; outdoors, make sure you’re sowing cool-tolerant crops or waiting until the ground warms a bit more, or use a greenhouse or cold frame for those needing more insulation.
Indoor germination setups should have good air circulation to discourage fungi from attacking the seeds or new shoots. Outdoor germination setups should be protected from seed loss due to predation, such as from soil-dwelling insects, birds, and squirrels or other rodents. Once in a while seeds don’t come up because they’re no longer there.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.