Watering Trees During Drought

Puerto Rico gets plenty of rain most of the year, so watering trees is not something most homeowners think about. Then the dry season settles in from December through April, a drought stretches longer than usual, and suddenly the mango is dropping leaves and the young flamboyán you planted last year looks like it is giving up.

Trees do not die from a single dry week. They die from a long dry stretch handled wrong - or not handled at all. Here is how to keep yours through the dry months.

Which trees actually need watering

Not every tree needs your help. Knowing which ones do keeps you from wasting water and effort.

Water these:

• Young and newly planted trees. This is the big one. A tree planted in the last year or two has a small root system that cannot reach deep moisture yet. These are the trees that die in a drought, and they die fast. If you plant during the dry season, watering is not optional.
• Fruit trees you care about. Mango, avocado, citrus, and breadfruit will drop fruit and stress under prolonged drought. If you want the harvest, help them through.
• Trees showing stress (see the signs below), regardless of age.
• Palms recently transplanted. Established palms are tough, but a newly moved royal or coconut palm needs consistent water to root in.

Usually leave these alone: large, well-established mature trees that have been in the ground for many years. Their roots reach deep and wide, and they are adapted to our seasonal dry spells. Watering them is rarely necessary and mostly wastes water.

The golden rule: deep and infrequent

This is the single most important watering principle, and most people get it backwards. Water deeply and less often, not a little bit every day.

A light daily sprinkle wets only the top inch of soil. That trains roots to stay shallow, right where the soil dries out and heats up fastest - which makes the tree more vulnerable to drought, not less. A shallow-watered tree is a fragile tree.

Instead, soak the soil deeply so water reaches 8 to 12 inches down, then let it dry out somewhat before the next deep soak. Deep watering pulls roots down to where the moisture lasts, building a tree that can handle dry stretches on its own.

A rough guide for the dry season:

• Young or newly planted trees: a deep, slow soak once or twice a week, more often in the first few weeks after planting.
• Establishing fruit trees or stressed trees: a deep soak roughly once a week during a real dry spell.
• Adjust for your reality: sandy coastal soil drains fast and needs more frequent watering; heavy clay in the interior holds water longer and needs less. Feel the soil a few inches down - if it is still moist, wait.

How to water so it counts

Slow and low. The goal is to let water sink in, not run off. A slow trickle from a hose laid at the base for 20 to 30 minutes, or a soaker hose looped around the root zone, beats blasting it with a sprayer. On our slopes especially, fast water runs off before it soaks in.

Water the root zone, not the trunk. Feeder roots spread out to and beyond the edge of the canopy. Water in a ring out toward the drip line, not just at the trunk.

Early morning is best. Watering in the morning lets the tree take up moisture before the heat of the day and lets any wet foliage dry, which reduces fungal problems in our humidity. Avoid the hottest part of the afternoon, when much of it evaporates.

Mulch multiplies your effort. A 2-to-4-inch ring of mulch around the tree (kept off the trunk) can cut evaporation dramatically, so the water you give lasts far longer in the soil. In a drought, mulch and watering work as a pair.

The signs a tree is drought-stressed

Catch these early, because a tree can be in trouble before it looks obviously sick.

• Wilting or drooping leaves, especially leaves that do not perk back up in the cool of the evening
• Leaves yellowing, browning at the edges, or scorching and dropping out of season
• Early leaf drop - a tree shedding leaves to reduce water loss is a tree under stress
• Curling or folding leaves trying to conserve moisture
• Dry, cracked soil and a canopy that looks thin or dull

For fruit trees, sudden fruit drop during a dry spell is a classic drought signal. If you see these signs on a young or valuable tree, start deep-watering promptly.

What not to do

• Do not overwater. Drowning a tree is as real as drying it out. Constantly soggy soil suffocates roots and, in our humidity, invites root rot. Deep soaks with dry-down periods in between - not a permanent swamp.
• Do not fertilize a drought-stressed tree. A thirsty tree cannot take up fertilizer well, and the salts can burn stressed roots. Water first; feed later, once it recovers and the rains return.
• Do not ignore a young tree because "it rained last week." In a real dry stretch, one rain is not enough for a shallow-rooted young tree. Check the soil, not the calendar.

When drought becomes a hazard

There is a safety side to prolonged drought most people miss. Severe or repeated drought stress can quietly weaken a tree - killing branches, inviting pests and disease, and compromising roots. A tree that struggled through a hard dry season can be more likely to drop limbs or fail when the wet season storms arrive. Drought stress in the spring can show up as a hazard in the fall.

If you have a mature tree that took a hard hit from drought - major dieback, large dead limbs, thinning canopy that never recovered - it is worth having it assessed before hurricane season, not after.

If you are not sure whether a tree is drought-stressed, salvageable, or becoming a hazard, we are glad to take a look and give you a straight answer. Call (787) 513-9441 or request an orientation. We are licensed and insured, serve all 78 municipios, and dispatch 24/7 for storm emergencies.