Over the summer months keeping plants well watered can be a challenge. The method chosen to water plants has a significant impact on how much water is absorbed by plant roots. Irrigation systems like soak hoses and dripper irrigation systems that water into soil, rather than onto plants, are the most efficient - they ensure plant roots grow deeper and are more resilient to dry conditions.
Choose plants that suit your soil type (i.e choose succulents for sandy soil) and group plants with similar water requirements together. This will automatically set up your garden to have plants with the same watering needs together and avoid over-watering other plants. Soil in pots dries out faster than soil in the garden so group your pots together. By minimising their exposure to the sun this will help to stop them drying out.
As a general rule you only need to water every 3-5 days (this may increase in summer, especially on edible crops). Less frequent, deep soakings encourage plant roots to grow feeder roots deep into the ground in search of water. This helps plants to better survive short term drought.
Check the moisture of your soil. If the soil is moist 10 centimetres below the surface it should be fine, if it is dry at this level it needs to be watered. In hot weather you may want to check the moisture every four to seven days.
Overwatering plants can do as much damage to the health of plants as not enough water. A damp growing environment will make plants vulnerable to diseases like root rot, blackspot and mildew. A diseased or stressed plant is also more likely to become a home for pests.
Use a combination of water saving techniques in the garden to ensure the best results.
General watering tips
- Use roof-collected rainwater or 'grey water' from the bath or washing machine to water shrubs.
- Collect rainwater in tanks or barrels. This will save money on your water bills.
- Ask your local council about water efficiency checks.
- Raise lawn mower blades in hot weather to prevent lawns getting stressed and leave clippings on the lawn as mulch.
- When you clean your fish tank, use the 'old' nitrogen and phosphorous-rich water on your plants.
Watering methods
- Water early morning or in the evening to avoid water loss through evaporation. Water droplets on leaves in bright sunlight can act as lenses, concentrating the sunlight and burning foliage.
- Apply water close to the ground and aim along the dripline of plants (which is beneath the outer edge of the plant’s canopy).
- Water the highest parts of the garden first: any run off will go to the lower dry areas.
- Adjust sprinklers so they do not spray on paths, driveways and against buildings.
Water saving products
- Apply SaturAid granular soil wetter like to garden beds, pots and lawns to assist water in reaching the root zone of plants.
- Mulch with Tui Pea Straw Mulch or Tui Mulch & Feed -the convenient two-in-one combination provides the benefits of mulching whilst the healthy additions of blood and bone, mulching straw and sheep pellets replace vital nutrients used by your plants.
- Compost is an excellent water saver, it improves the soil by increasing moisture holding capacity, particularly in sandy soils.
Maintenance
- Check your irrigation, taps and hoses for leaks. A dripping tap can leak up to 10 litres of water a day.
- Use a soak hose in garden beds rather than a sprinkler.
- Remove weeds, they compete for the moisture and nutrients.
- Use cloches or growing tunnels to help retain soil moisture.
- Give plants an application of Tui Organic Seaweed Plant Tonic plant tonic at least every month to make them thrive and help them cope with temperature fluctuation.
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Water Saving Guide Comments
I saw a woman buying Saturaid the other day and I thought it was a gimmick but now I see from your article I was wrong, especially for plants in pots. Looks like I will be buying some tomorrow. Thanks Tui.
Janice Austin
Hi Janice, Saturaid is especially good to use in dry areas of the garden, such as under the eaves where it can get very dry and rain does not fall. It is perfect for terracotta pots and hanging baskets to help retain moisture - a must have for the summer garden.
The Tui Team
Saturaid is especially good to use in dry areas of the garden, such as under the eaves where it can get very dry and rain does not fall. It is perfect for terracotta pots and hanging baskets to help retain moisture - a must have for the summer garden.
The Tui Team
When watering the gardens with a sprinkler, if I put a bucket beside the garden how much volume of water is adequate
Catherine
How much water applied to the garden and for how long will largely depend upon what your soil is like and what plants are growing in the garden. The more organic matter in your soil, the better water retention will be, and the addition of mulch to the soil surface will also help prevent drying out as quickly. The water needs to penetrate at least 10cm down into the soil, so collect 5cm of water in your bucket and then check how far down the water has penetrated. Deep watering (30 minutes each time, depending upon the water source and availability) is preferable to light sprinklings of water as deep watering encourages roots to penetrate down into the soil so they stay cool and moist and get better protection from drought. Light sprinklings encourage roots to stay on the surface and so plants are more likely to dry out. Watering frequency is every 3-5 days (weather dependent) but in the hot summer months it could be daily.
The Tui Team
To save water I bought a square bucket to fit into my kitchen sink to capture all the hand washing, potato rinsing, dishwashing water throughout the day. Astonishingly I have to empty the bucket about 6-8 times daily, that's 60-80L of grey water from the kitchen alone. I use it to water the garden. I use old fashioned real soap so no harm done to the plants.
Fiona Baker
Excellent advice and explained really well.
Sheila Findlay
I collect water in a bucket and bowl while waiting for hot water to come through in the shower and kitchen.
Joyce Dixon
I’m trying to figure out how much water various plants in my vegetable garden need. I’m on tank water so water conservancy is a must. Has any of your team done a plant water requirement experiment?
Bob
Hi Bob, this is a common question and unfortunately there is no right or wrong answer! Different plants have different water requirements, soil type and whether there is enough organic matter in the soil to retain moisture, region and climate, as well as the type of plants being grown, all influence how much and when you need to water. Most gardeners don’t have the luxury of space and so have mixed vegetable plantings and so aren’t going to water each plant individually. If you understand the water requirements of your plants, which ones need regular watering and which ones can be stretched, it will make your watering much more effective. Tomatoes need deep watering every 2-3 days rather than light daily sprinklings so that fruit are flavourful and not mushy and watery. Chillies on the other hand are better with less water to increase the heat intensity of the fruit. Deep watering is preferable to daily light sprinklings as plant roots will come to the surface to get water rather than draw it from deep down, so there is more chance of them drying out. Deep watering means water needs to penetrate 12-15cm down into the soil. There is a simple way to test how much water is being applied to the soil. You can purchase a rain gauge from a garden centre or hardware store, or a more DIY method is to get a tuna can or similar, mark 2.5cm from the bottom of the can. When the water from rain or watering collects in the can and reaches 2.5cm, the garden will have received 2.5cm of water penetration over the whole area. This is enough water for most plants for a week, with the exception of lettuce, celery, spinach, cucumber, brassicas and other leafy greens which need frequent watering. A water metre probe is also an effective way to know if the soil is dry or if plants need watering. The key to water retention is plenty of organic matter in the soil, this could be compost, sheep pellets or well-rotted grass clippings. Applying mulch such as pea straw, barley straw or Tui Mulch & Feed helps with water retention. A simple test will tell you how moisture retentive your soil is, pick up a handful of soil, close your fist, then open it and if the soil crumbles away and does not hold its form, it needs watering and would benefit from the addition of organic matter (as well as water). If the soil holds in a ball, with a few crumbly bits, then the organic matter in the soil is good and will make your watering more effective. Another way to test whether the soil needs watering is to push the index finger into the soil, if at 2.5cm it feels damp, you don’t need to water, if it feels dry, you do.
Without knowing what vegetable plants you are growing, here is a rough guide to watering. There are three stages.
Other things that can be done is water in the morning, if later in the day the water evaporates and at night plants don’t have time to dry out overnight and so are more susceptible to fungal disease such as powdery mildew.
Direct water applied to the soil using a watering can, irrigation drippers or a soaker hose, rather than overhead sprinklers, it is much more efficient and direct watering. Allow the soil surface to dry out between watering for fungal prone vegetables such as potatoes, courgette and tomato.
There is a measure of “one inch of water per week” which is a one inch deep layer of water over the soil surface. This is an American measurement, but to convert it to New Zealand it would be 2.5cm of water per square metre of garden per week, I round up the inch to cm conversion to 2.5cm. You are measuring millimetres of soil depth, not millilitres of water.
Lianne