“The leaves started drooping yesterday. My plant does not look good. Can it be saved?”
Water may be the problem
Water (either too little, too much or at the wrong time) is a primary cause of death for garden plants. To figure out what is going on you should start by checking the soil. If it is damp where the roots are, then over watering or watering when the soil is warm may be the culprit. Watering warm soil creates conditions that support the growth of pathogenic bacteria and fungi. Native plants adapted to dry summers are especially susceptible to these pathogens. Water is present but the plant can not absorb it due to root damage. These plants usually do not recover. The only thing you can do is cut the water, let the soil dry out and see what happens.
If the soil is dry and the plant perks up when watered, it was thirsty due to too little water. Water deeply and hope it was not too stressed to recover. Be aware that some plants will droop during the heat of the day but recover as temperatures cool down. As long as they perk up when the sun goes down, hold off on water.
Young plants, those not yet established, are most vulnerable during severe weather. Their small size and undeveloped root systems make it hard for them to survive weeks of extreme heat. Yet, water and warm soil often lead to root rot. So it seems that watering is bad and withholding water is bad. Observing your plants carefully—looking at the leaves, both old and young and the buds—can tell you a lot about what they need. When old leaves turn yellow and drop, this may just be part of your plant’s normal seasonal cycle. It is common in sages, monkey flowers and some Ceanothus. When the younger leaves and buds dry up, you probably have a problem. If the whole plant wilts, this is a bad sign as well. When stem tips and leaves droop slightly the plant most likely needs water. If you must irrigate in the summer, try to do it when the soil is cool, such as early morning or on foggy, cool days.
Keeping trees healthy
It is particularly upsetting when we lose older plants, especially trees. There are many reasons a tree may fail, but again, improper watering is a common culprit. Coast live oak is an important example. This tree is susceptible to Armillaria mellea (oak root fungus) which thrives in moist, warm soil. To avoid diseases and maintain overall health, you should not provide summer water to established coast live oaks that predate your home and garden. Young trees will need summer water during the establishment period which can be two to three years. Other trees that are adapted to summer water, even coast live oaks, will need continued summer irrigation. Try to water early in the morning when the soil is cool.
Construction near trees, especially under the canopy, also can be very detrimental. When making changes to your yard, or planting near a mature tree, ask yourself: Which is more important, the hundred year old tree or the changes you are contemplating? Are the azaleas that will give your yard added color more important than the majestic oak tree that provides shade for your home and food for the birds? Do you need a functioning sewer system for your house, even though digging up the broken pipes may put your tree at risk? In the first case, you should rethink your plans. Obviously, the answer in the latter example is: yes the sewer system is critical to your home, but maybe you can divert a new pipe around the canopy of the tree. Be especially careful when changing soil grade near established plants. Trees and plants absorb much of their water and air from roots that are found near the surface of the soil. Removing soil will expose and damage these roots. Adding soil reduces aeration and can suffocate them.