Good drainage is essential. Keep the soil moist. Don’t let the tree dry out. In the ground maintain a deep basin as wide as the tree. Citrus need a most soil and air for roots – avoid airless and soggy soil. Allow time for it to drain between waterings. In light, well-drained soil, water established trees about once a week in dry weather. In heavy clay soils, the air spaces are tiny. Excess water cannot drain away rapidly. Water deeply every two to three weeks, or more in dry weather. Allow time for it to drain and the surface to dry out, but don’t go so far as to let new growth wilt. In well-drained containers, water about twice a week in normal summer weather – more often during hot spells – less frequently in the winter. Newly planted trees need more frequent watering until they are established. If new growth wilts or leaves are dull, you are waiting too long to water. If you observe excessive fruit and leaf drop a few days after a heavy watering, the tree became too dry before it was watered. In the future, be thorough and consistent – don’t let the tree dry out.
Know where the graft is on your tree. Remove all growth below it – it is worthless and takes vitality away from the top. This is especially so with younger trees. Suckers are generally very vigorous and thorny and have quite a different leaf than the top. Remove them as soon as observed.
Even though we discourage pruning, trees may be pruned to any desired shape. They will look fuller with occasional pruning to shape leggy branches. Pinching back tips of new growth will help trees to round out. Some trees may develop erratic thorny juvenile growth above the graft. If so, cut it back at any time. Avoid pruning in cold winter months to ensure best protection against cold. Pruning can be done any other time of the year.
Liberal use of mulches will conserve precious water. Less water is needed as evaporation is reduced and weeds are inhibited. To avoid root diseases, keep mulch at least 6” away from the tree trunk.
Trees may set more fruit than they actually produce: there will be a certain amount of fruit that will fall off. Only 5% of the initial flowering on a healthy tree can develop into a normal crop. When a mild spring turns to hot summer, the tree is under stress. When dry winds coincide with insufficient watering, the tree is under stress. Lack of fertilizer at proper times in the spring will cause stress. Application of fertilizer after flowering and before the fruit is golf ball size will cause stress and fruit drop. During critical fruit development trees should be watered sufficiently.
Citrus are heavy feeders. It is best to use a balanced fertilizer, which contains nitrogen, potassium and phosphorus (18-6-12, for example) and trace elements such as iron, zinc and manganese. Fertilize regularly as directed on the label. However, we recommend fertilizing lightly all year round. Yellowing leaves are an indication of lack of fertilizer or poor drainage.
Citrus trees may develop deficiencies of minor food elements. Zinc, iron and manganese are important elements, especially for younger trees. We recommend using a citrus food that has at least these three elements. Check the fertilizer label. It will list the amount of nitrogen, potassium and phosphorous, as well as any minor elements.
Salt burn is the appearance of brown dry edges around the leaf or spots, similar to a burned leaf. Improper watering and poor soil drainage, as well as improper feeding usually bring this problem on. To correct salt burn apply gypsum and Dispersul in February along with regular citrus feeding and again in May and September. Gypsum is inexpensive and will keep your soil free of salt buildup. Apply at the following rates: Dispersul – two pounds per 100 square feet; Gypsum – five pounds per 100 square feet. Do not feed nitrogen to plants showing signs of salt burn until you have corrected the soil problems. This could also have a burning effect on the trees.
Fortunately, citrus have few insects. Aphids can appear in early spring as well as thrips, which cause crinkled leaves and also red mites. Since trees have edible fruit, insecticides should be used sparingly and carefully. Keep tree free from insects by washing dust off foliage occasionally with water. Always read and follow all directions carefully on pesticide labels and wear required protective clothing. Measure amount to be used carefully to prevent damage to tree. There are insecticides available for use on citrus at both Harper’s locations. We don’t recommend spraying if the temperature is above 90 degrees or below 40 degrees, or if it is windy.
The age, location and condition of the tree, and degree and duration of cold determine possible frost damage. Frost warnings and reported frost damage generally refer to the fruit, not the tree. Older, established tree have survived prolonged cold spells down to 26 degrees with little difficulty. It’s not much of a chore to move or cover your dwarf tree if a cold night is forecast. Frost cloth can be left on during the day if needed. Do not trim freeze damaged trees until new growth pinpoints the dead wood.
Gummosis is a fungal disease caused by exposing trunks of citrus to too much moisture. It is also known as Brown Rot Gummosis and Foot Rot. It is a brown gummy discoloration of the inner layer of the tree. If it goes completely around the trunk it may kill the tree. To prevent, never let trunk stand in water. Build a berm around but away from trunk to keep irrigation water from wetting it. If the trees are infected, remove discolored bark to the point just beyond the infection and treat with a Bordeaux paste mixture.