WATER WISELY!

What to do when heat and drought threaten your plans for that beautiful garden?  The answer is not just to water but to water wisely!  The short version: water deeply and you can water less frequently with better results.  Water shallowly and you’ll have to water a lot more often to maintain shallow roots that are vulnerable to drought and to that long weekend away when you thought you had convinced your home-from-college offspring to water.

When? Sometimes you can tell visually.  Lots of plants will perk up when they get enough water – roses, hydrangeas, deciduous plants in general and some broadleaf evergreens as well.  But sometimes you can’t tell visually until it’s too late – evergreen needles will “suddenly” turn brown and drop and some perennials with tender leaves will crumple within hours when stressed too far.

How to know for sure? You have a great moisture meter right at hand – your fingers.  Stick a finger in the dirt to feel the soil.  Cool and moist?  Don’t water but do check again the next day. For small plants, you’ll want to test at about 3” deep; for shrubs and trees 5 to 6” deep is better.

How much and how frequently? There are lots of ways to describe how much water to give a plant.  Remember that your goal is to give enough water to permeate the entire root ball and the surrounding soil.  So, think in terms of watering the area you want roots to enter rather than watering just the roots themselves.  A general rule of thumb is to give about 2 gallons per foot of plant height or width.  Water once a week with extra waterings in the early weeks after planting and during heat waves or drought.

Is my irrigation system doing enough? For established plantings your system may be set up to be totally adequate, but for new plants most systems can’t meet the total watering requirements of any but the smallest plants.  Irrigation systems are usually run every few days and only for a few minutes, penetrating the soil only a few inches.  Think back to the size of the root ball of that plant you just bought with good money and decide whether it was only a few inches deep.  And irrigation systems are usually turned off for the season long before new plants stop needing regular water.

Can I water too much? Yes.  Roots must “breathe” as well as take up nutrients and water from the soil.  If the spaces between soil particles are too often filled with water, the roots will smother.  In poorly drained soils you must water less (and in quickly draining soils you must water more, of course), but you always need to allow your plant to catch its breath between waterings.

Any special technique? For shrubs and trees I prefer to leave a garden hose sans nozzle on a very, very (did I say very?) slow trickle for however long it takes to get enough water down.  Gravity does the work of pulling the water down and capillary action does the work of drawing it sideways through the soil.  I can go do something else!  For perennials watering at the base of each plant with a wand is ideal.  The point is to water the roots rather than foliage — wet foliage is susceptible to fungi.  Soaker hoses and tree-gators and hygroscopic gels are all great products when used correctly and not expected to work miracles (for example, filling a tree gator once will not water the tree for the entire month you’re in the south of France).  Ask at your garden center about how these products can perform their best.  Building a “saucer” around the plant can be used to capture water before it runs away on slopes as well as to help measure how much water is being given.

Mulch helps? For sure.  You can greatly reduce evaporation from the root area of plants by using a layer of mulch – up to 1” for perennials and no more than 3” for shrubs and trees.  Remember, no mulch against trunks, branches, or crowns of plants.

New versus old plants? Depends on the definition of “old”.  Any plant going in this year needs regular watering.  And any plant going in this year will need regular watering next year.  Any plant in the ground longer than two years still deserves a drink when times are rough.

What time of day? If you can, water in the morning.  This allows wet foliage to dry quickly so disease is less likely.  Morning watering also means a plant has the resources it needs to face a tough day rather than your trying to make up for the stress after the fact in the evening.  By then, tissue damage, particularly of thin, soft leaves, may be irreversible.

How late into the season? Through Thanksgiving!  Especially for broadleaf evergreens!  This is the best insurance that your plants will survive the winter in good shape.  That last deep drink before the ground freezes is so important.  I hear over and over that people stop watering with the first frost because they think that’s when the ground freezes not realizing that their plants still need watering right into the beginning of December.  So, even if it means hauling hose, it’s the best way to insure your investment!