By Dr. Leonard Perry, Extension Professor
University of Vermont
There's no doubt about it. Container gardens are an attractive way to add color to a patio or porch, or satisfy the urge to garden if you have a green thumb but limited space in which to plant flowers. But as easy as they may be to plant, they do need care throughout the season to ensure healthy plants and continual bloom.
If the container plantings you did in spring are beginning to look a little leggy or the foliage is yellowing, don't despair. The Plant Doctor is in. Here's a list of common problems--and the solutions--to help you get your container gardens back on the road to recovery:
PROBLEM: You water regularly, but wilting still occurs.
PROBABLE CAUSE: Poor drainage and aeration of soil.
SOLUTION: Repot using a lighter soil mix containing more organic matter. Or, if that's not a viable option, increase the number of drainage holes in the container.
PROBLEM: Plants are tall and spindly.
PROBABLE CAUSE: Low light and high nitrogen levels.
SOLUTION: Move the containers to a location that receives more sun or light a day. Stop fertilizing the plants, or decrease the amount.
PROBLEM: Plants have stopped flowering.
PROBABLE CAUSE: This may be natural for this variety. However, if you planted annuals, deadheading (removing spent flowers) often promotes branching and rebloom. If the buds don't open, the cause could be disease and rots. Too much fertilizer can cause excess leaf growth at the expense of flowers, so fertilize less if the plant is lush but has no flowers.
SOLUTION: Deadhead plants as mentioned above, keep good air circulation to avoid disease, and avoid watering late in day to allow foliage time to dry before night.
PROBLEM: Yellowed foliage, especially the lower leaves.
PROBABLE CAUSE: Too much water or too little fertilizer.
SOLUTION: Water plants less often, and make sure the container has adequate drainage. In addition to water less, fertilize more, especially if using low nutrition organic sources.
PROBLEM: Edges of leaves are brittle and dry.
PROBABLE CAUSES: Too much salt is present in the soil, most likely from overfertilizing. (You might notice a whitish crust on the soil surface, another sign of excess salt.) Moving containers quickly from shade to more sun also may be the cause.
SOLUTION: Water generously--until water pours out of the drainage holes--to cleanse the soil and remove the salt. Avoid changing locations and light levels rapidly.
PROBLEM: Leaf spots, powdery or rusty areas.
PROBABLE CAUSES: Low temperature, inadequate phosphate, or disease.
SOLUTION: Move the container to a warmer location. Apply a fertilizer containing high phosphate. You also might try fungicide although if the problem is serious, you probably will need to toss the plant.
PROBLEM: Foliage is riddled with small holes.
PROBABLE CAUSE: Insect pests.
SOLUTION: Work with your local garden center or call the University
of Vermont Extension Master Gardeners' hotline at (802) 656-5421 or toll-free,
1-800-639-2230 to identify the pest. Then apply the least toxic insecticide
that will do the job, following the instructions on the label carefully.