Issue 30 • Seasonal tips and featured varieties coming to a retailer near you • June 18, 2009

Watering Your Garden

It’s almost here….
Summer officially arrives this weekend, with summer solstice at 10:45 PM on Saturday, June 20th.  As warm, dry weather settles in, it’s important that vegetable plants receive the right amount of water at the crucial stages in their development.

Watering Methods

Most Northwest gardens can’t depend on rains to supply much moisture in the summer, so it’s up to gardeners to get water to their plants.  Depending on your garden setup and size, available time and money, and preference, this may mean watering by hand, laying out drip or soaker hoses, setting up an overhead sprinkler, or some combination of these methods.  Each has its pros and cons: 

Watering by hand with a hose is simple and cheap, without investment in any specialized irrigation equipment.  It’s also precise, allowing you to water only the plants you need to and keep water directed at the ground to avoid wetting the foliage.  Use a watering wand with breaker and valve for best control. However, if you have a big garden, it can take a long time, and unless you have a very simple layout with straight rows and wide aisles, it can be complicated dragging the hoses around to reach everything (without knocking over all the other plants in the way).  

Sprinklers are also easy and cheap, but will soak everything, including foliage and ripening fruits.  Diseases often spread more easily when leaves are wet and some fruits can develop soft spots or start to rot if they get wet and stay wet.  If you garden on a hill or have clay soils, sprinklers may water too fast, with water running off of beds rather than soaking in to reach vegetables’ roots.  This is the least efficient method, losing a lot of water to evaporation and runoff.

Soaker hoses or drip irrigation systems let you water very precisely (right at a plant’s base, keeping foliage dry), very slowly (so water can seep down to the roots), very easily (once it’s set up, you just turn on the hose – you can even put it on a timer), and very efficiently, with all the water soaking into the soil where plants can use it.  The downside is that it costs more and is more complicated to set up each season.  Hoses also need to be rolled up and stored for the winter.
 
For more on how each of these methods work, plus a few other suggestions, see:

http://extension.oregonstate.edu/catalog/html/grow/grow/water.html
http://msucares.com/lawn/garden/vegetables/watering/index.html
http://www.vegetableexpert.co.uk/WateringSystems.html

General Watering Guide

However you decide to get the water to the plants, keep these tips in mind:

How often and much to water? 
Depending on the climate and soil composition, most vegetables need one or two inches of water per week.  Hot, dry, sunny and/or windy weather will increase the need for irrigation, as will sandy, fast-draining soils.  Cool, humid, cloudy, still weather and clay soils decrease the amount you’ll need to water.  Usually, soil in the root zone should stay consistently moist but not so waterlogged that roots get suffocated.  It’s best to water deeply but infrequently (every 5-7 days in hot weather), to encourage the development of strong, deep root systems.  Shallowly rooted vegetables (like lettuce or radishes), recent transplants, and germinating seeds will need to be watered more often but less deeply.  The best way to check if it’s time to water is to stick a finger down into the soil about 2 inches deep.  If it feels moist, the plants still have water available to their roots; if it’s dry, it’s time to water.

When to water? 
It’s best to water in the morning.  This has several advantages: it’s cooler, so you lose less water to evaporation; plants are less likely to spread diseases if their leaves have time to dry off before the cool evening sets in; and the soil will have a chance to warm back up in the heat of the day, so plant growth doesn’t slow.

Soils, especially clayey ones, can develop a crust on top that causes water to run off rather than soaking in.  To keep this from happening, cultivate the area around plants, lightly breaking up the surface of the soil with a small rake or hoe before watering.  Don’t go too deep, or you’ll disturb plant roots; just fluff up the top layer enough that water has pockets and cracks to seep down into.  Digging a shallow trench next to a row of vegetables or forming a low “bowl” of soil around each plant also helps direct water to the roots.  Fill the trench or bowl, letting water slowly soak down before you fill it again.  This is probably best done as you sow or transplant, however, so you don’t disturb a plant’s roots once it’s established.

Containers always dry out more quickly than the ground, so check them often if you’re gardening in patio pots or hanging baskets.  Water containers slowly enough that soil doesn’t wash out the top, but long enough that water reaches all the way to the bottom. 

And, of course, try not to over water – that can leach nutrients from the soil and even drown plants’ roots, depriving them of the oxygen they need to grow.  Deep, infrequent waterings allow the top inch or two of soil to dry out and keep plants from getting waterlogged.

Plant by Plant

Consistent water is especially crucial during certain stages for each type of vegetable.  Below is an overview for some of the most popular garden veggies.  For a more complete, detailed list, see:
http://www.harvestwizard.com/2009/05/watering_vegetables_critical_t.html

• Beans (green, lima, dry, etc.) – during flowering and pod formation
• Broccoli, cauliflower, and cabbage – during head formation
• Carrots, turnips, radish, beets – when forming roots (basically from sowing to harvest)
• Corn – as silks, tassels, and ears form
• Cucumbers – during flowering and fruit formation
• Lettuce and greens – consistent even moisture from sowing to harvest
• Melons – as buds, flowers, and fruit develop
• Onions, garlic, shallots – as tops grow and bulbs start to enlarge (see note below)
• Peppers, tomatoes, eggplants – flowering through harvest (see note below)
• Squash and pumpkins – as buds, flowers, and fruit develop (see note below) 

NOTE: Sometimes withholding water can be helpful in encouraging plants to ripen their fruit.  If you cut off all watering in mid- to late- August, tomatoes will put their energy into ripening their existing fruits rather than setting new ones that won’t mature before frosts.  For longer-storing onions, garlic, and shallots, stop watering when the foliage starts to turn yellow, so their outer skins start drying out before harvest.  When the leaves of winter squash or pumpkin plants start to yellow in the fall, stop watering so they can start to dry out and develop hard rinds for storage.

Previous issues of Garden News are in the Log House Library.