Some times these baskets have dried out in between waterings, so there are some leaves that are brown and dried. In other cases the soil has been kept too wet and the plants are yellowing from over watering. Some annuals slow their flowering because they haven't been deadheaded…
If a plant is overwatered, it will likely develop yellow or brown limp, droopy leaves as opposed to dry, crispy leaves (which are a sign of too little water). Wilting leaves combined with wet soil usually mean that root rot has set in and the roots can no longer absorb water.
In general, water plants in hanging baskets when the soil surface becomes dry to the touch. On hot, sunny days it may be necessary to water once a day. When watering hanging baskets, be sure to apply water until water begins to flow out the bottom of the container.
Aphids, thrips, spider mites, budworms, cucumber beetles, earwigs, slugs… these can all wreak havoc on annuals in baskets. It can seem a little overwhelming, so let us simplify. Aphids are very common.
If there is one single factor beyond water that makes all the difference in keeping hanging baskets thriving – it's fertilizing! Hanging basket plants have a limited amount of nutrients within their soil. And once those resources become scarce, the plants will start to suffer.
If the flowers in your baskets wilt, the roots will also shrivel making it harder for them to absorb water. Give your baskets a thorough soak but catch the run-off in a bucket and return it, along with the nutrients it contains, to the basket. Your plants need those nutrients to flower well.
I recommend water soluble fertilizer, as it's easy to use, and ensures the roots can absorb the nutrients. I always use a 15-30-15 with micro-nutrients for my hanging baskets. You can either use it every second watering at full strength, or (my personal recommendation) use it every time you water but at 1/2 strength.
Try to hang your baskets near a fence or wall, which will help block out some of the wind. Be on the lookout for over-sunned flowers. While most annuals love lots of sun, sometimes direct sun can be too much of a good thing.
Too little, and they're drooping like a wilted teabag. Too much, and they get a soggy bottom and grumpy leaves. Overwatering means yellowing leaves, a general feeling of flop (science calls it wilting!), fuzzy soil, and a pot that feels like it could double as a weight.
Use a good quality multi-purpose compost, for example a loam-based compost, and add perlite to help with moisture retention and drainage.
The good news is that most plants will bounce back between 7-14 days if they're given proper care (which includes rehydration). If this isn't possible because major damage was done or little healthy root system exists then expect about 2 weeks until improvement can be seen.
A: I've seen some seriously wilted plants make miraculous recoveries from death's doorstep, but there is a point of no return. Here's what I'd do. Take the basket down and place it in a shaded spot. Then give it a good soaking at least once a day until the water runs out the bottom.
To revive the plant, you can soak it in water and then adopt a predictable watering schedule that uses the same amount of water each time. Remove dead leaves: Improper care may cause most leaves on the plant to die, and it's usually best to remove leaves that have become entirely brown.
However, the plant will respond the best if you'll go ahead and mix up something like Miracle-Gro or another liquid fertilizer into your water. That's because liquid fertilizer is instantly available to the plant and it will respond quicker than with the Osmocote.
How often should I water them? In the heat of the summer you should be watering your containers and hanging baskets every day. On hot, windy or humid days you may need to water more than once. And on rainy days you may not need to water at all.
Trim the Hanging Basket
Here is the hard part for some people, but it is always easier for a plant to grow new growth than it is to fix the old growth. We need to take a pair of scissors and give your basket a haircut. This makes your basket so much better. You give all the stragglers a nice trim all the way around.
How to check for root rot. The main signs to look out for are: yellowing, wilting leaves, wet soil that isn't drying, black, wet roots, quickly declining health, and stunted growth.
When a plant is first becoming overwatered, leaves turn yellow. If soil doesn't have a chance to dry out before you water again, leaves start to wilt. When overwatering is the problem, wilted leaves are soft and limp. (If too little water is the issue, wilted leaves are dry and crispy.)
Feeding. Types of feed you may need to use: high nitrogen feed for growth; tomato feed for the flowers; and a balanced feed Miracle Grow for an all-round feed.
You may need to trim the plants back to within an inch or two of the base. Water your petunias thoroughly and keep the soil evenly moist. A flush of new growth will soon appear and produce new blooms. Within a few weeks your petunias will return to their previous vigor, as long as you keep them watered well.