Gadenin日本語Get the appWater deeply, then let the surface dry
The root system sits in the top six to twelve inches (15-30 cm) of soil, and it needs both water and air in that band. That means a soaking that wets the whole root zone, followed by a genuine drying of the top couple of inches before the next one. Little and often keeps the surface permanently damp and the roots permanently short of oxygen, which is exactly the condition root rot needs.
Test with your finger rather than a schedule. Push two inches (5 cm) into the soil under the mulch: if it is damp there, wait. In warm, dry weather a young tree in the ground typically wants a deep soak every five to seven days; a mature tree with a full canopy can go ten to fourteen days. In a container, expect to water two or three times a week in summer and perhaps once a fortnight in winter.
Cut back sharply in cool weather. A tree that is not growing is barely drinking, and winter watering at summer frequency is the single commonest way to kill an avocado in a pot.
| Situation | What you see | What to do |
|---|---|---|
| Too dry | Leaves fold upward along the midrib, wilt at midday and recover overnight | Soak deeply now; increase volume, not frequency |
| Too wet | Whole leaves yellow, dull and droop; wilt that does not recover overnight | Stop watering, pull mulch back from the trunk, improve drainage |
| About right | Firm dark leaves, soil damp at four inches (10 cm) and dry at one inch (2.5 cm) | Keep the same interval and watch as the weather turns |
A wilting avocado is more often drowning than thirsty. Before you reach for the hose, dig down four inches (10 cm) and check. Watering a waterlogged tree finishes it.
Brown, crisp leaf tips are salt, not sunburn
Avocado is among the most salt-sensitive fruit trees grown in gardens. Chloride and sodium move to the leaf margins with the transpiration stream and accumulate there, and the tissue dies from the tip backwards. The result is a dry, papery brown edge with a sharp boundary against healthy green, usually worst on the oldest leaves and worst late in the season.
The salt comes from the water and the fertilizer more often than from the soil. Hard tap water, softened water, water from a well in a dry region, and repeated light feeding without leaching all build salts in the root zone, and containers concentrate them fastest of all because nothing ever washes through.
The remedy is leaching: water heavily enough that a good volume drains out below the roots and carries the salts with it. In a container that means running water through until it pours from the drainage holes for several seconds, done every few weeks in the growing season. In the ground it means one deliberately generous soak, roughly double a normal watering, every month or two. Never use softened water, which trades calcium for sodium and makes the problem worse.
- Confirm the pattern Salt burn starts at the very tip and the outer margin, is uniform around the leaf edge, and shows on old leaves first. Sunburn is patchy and follows the exposed face of the canopy. Root rot yellows the whole leaf rather than just the edge.
- Leach the root zone Apply water slowly at twice the usual volume so it moves down past the roots rather than running off. Repeat after a week if the tree is in a container and the burn is severe.
- Cut the feed, not the water Stop all fertilizer for six to eight weeks. Fertilizer salts are the commonest cause in a well-cared-for tree, and the impulse to feed a browning tree makes it worse.
- Mulch and keep mulching A thick coarse mulch keeps the surface roots cool and moist, which reduces the concentration of salts they meet. It will not undo damaged leaves but it stops the next flush burning.
Mulch heavily, and keep it off the trunk
This is a tree that evolved under its own leaf litter. Four to six inches (10-15 cm) of coarse woody mulch, spread from a foot (30 cm) away from the trunk out to the edge of the canopy, does more for an avocado than almost anything else you can do: it keeps the shallow feeder roots moist and cool, buffers salts, feeds the soil biology that suppresses root rot, and stops the surface crusting.
Use coarse material with a lot of woody structure rather than fine compost. Chipped prunings, bark and even the tree's own fallen leaves are ideal; fine compost packs down, holds water at the surface and can smother the roots it is meant to protect. Leave a clear collar of bare soil around the trunk so the bark stays dry.
Feeding: little, often, and mostly nitrogen
Avocados are not heavy feeders and they resent being pushed. Split the annual nitrogen into three or four small applications through the growing season rather than one large dose, and stop feeding well before cold weather so the tree is not carrying soft growth into winter. Excess nitrogen at flowering time produces vigorous shoots that compete with the fruit and cause fruitlet drop.
Zinc deficiency is the classic avocado nutrient problem and looks distinctive: small, narrow leaves crowded at the shoot tips with pale mottling between the veins, and shoots that stop and restart in tufts. It shows up on alkaline soils and in containers. A foliar zinc spray in spring corrects it faster than anything applied to the soil, and it is worth confirming the pattern before treating, since the same tuft habit can simply be a tree recovering from cold.
In a container, feed at a quarter to half the label strength with each watering during the growing season rather than a monthly full dose, and leach thoroughly every few weeks to keep the accumulated salts moving out of the pot.
Keep a note of every feed: date, product and rate. When leaf tips brown, the record tells you in seconds whether you have been overfeeding, and it stops you guessing the same wrong answer two years running.