Leaf Scorch
If you search the internet for causes of leaf scorch, you will surely come upon many websites who will tell you that one of the causes of leaf scorch is watering your plants at midday when the sun is the hottest. The theory is that water conducts heat and that if the plant’s leaves are wet, the sun is more apt to burn them. This is simply not true. Watering a plant can never cause leaf scorch, no matter what time of day it is done.
Sometimes scorch is just an indication that the plant is not well-suited to the particular location where you planted it. Other causes are too high temperatures, drought, and hot winds. Roots that have been damaged can cause leaf scorch, as can ocean salt, or substances that enter the ground, such as chemicals, too much fertilizer, or the kind of salt used to melt ice in the winter. Some diseases, such as verticillium wilt cause a water imbalance which also can promote leaf scorch.
Certain kinds of plants are more apt to have leaf scorch than others. These include rhododendron, flowering dogwood, birch, beech, white pine, ash, oak, horse chestnut, and several kinds of maples, including the Norway maple, sugar maple, and Japanese maple. If your plant gets leaf scorch, the symptoms can be yellowing of the leaves, especially between leaf veins and along the leaf edges. There will be brown at the tips of the leaves.
Sometimes there is no yellowing at all and leaves just go quickly to brown and often curl or wither and die. It is rare that the entire plant will have leaf scorch at one time. It is most often the part of the plant facing the sun or the side most prone to wind damage. On fir trees, the brown begins on the tip of the needles and then progresses downward until the whole needle is brown.
You can water your plants any time of the day if they are dry. The morning is the best time because then the water has all day to soak down into the roots of the plant. The best way is to allow it to soak slowly. Watering at night can promote some types of fungi on some kinds of plants. Because leaf scorch is caused by drought, another way to help is to mulch your plants. Wood shavings, chips, or bark are all good mulch materials.
Be careful when you apply fertilizers that you do not get too close to the roots. Spring and fall are the best times to use fertilizer. Also making sure that you prune off any dead or diseased branches each year can affect the overall health of the plant which guards it against leaf scorch. If you know that your plant has been damaged by salt, washing it off thoroughly within twenty-four hours may keep it from developing leaf scorch or worst of all, dying.