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Weekly Gardening Guide: Watering!

July 23, 2015

Water water everywhere and not enough to drink!

Now that we are into the hotter, dryer depths of summer, we thought it might be a good time to talk about watering.  How often, how much, and when?  And how do you know when you’re doing it wrong?
Naturally, the answers vary depending on the situation.  Do you have sun, or shade?  Clay soil, or sandy?  Windy or calm?  Different types of plants need different amounts of water as well. Annuals in general, and specifically annuals in pots, need plenty of water.  In the sun, this usually means every day.  In a shady spot, this could be daily or every other day.  Some perennials have ongoing watering needs, and occasionally trees do as well. 
However, there are some general guidelines you can follow that apply to the average situation, and you can tailor these to your specific circumstances.  Remember, there are no solid rules to watering!

How to Water:
Apply water to the soil around the base of the plant, preferably in the morning.  Keeping water off the leaves reduces the likelihood of fungus and mildew, and makes leaves less appealing to slugs and snails.  Watering in the morning allows water on the leaves to evaporate more quickly, to further reduce these conditions.

 Water slowly and thoroughly.  Don’t apply more than the soil can take in within a few seconds, and keep watering until you have watered below the rootball.  This can be hard to gauge, and our best suggestion is to imagine the plant still in its pot and estimate if you have wet all the soil in the pot yet.  You could even practice this while the plant is still in the pot, so you have a good idea of how much water is needed.  Deep, thorough watering is especially important for trees because they have so much foliage to maintain and more roots to establish.

When to Water:
Newly planted perennials and trees always need to be watered, even if they are considered to be drought tolerant.  Water them at the time of planting, and then around every other day for the first week.  If the soil is still very moist, skip that day. 

 After the first week, you can use the 3-2-1 rule for most perennials and shrubs.  This means you would water 3 times in the nest week, twice the week after that, and once after that.  At this point, the roots should be nicely settled in and you will be seeing some vigour and signs of new growth.  You have successfully established your new plant!  Beyond this point, you may water once every week or two, depending on how sunny/windy/rainy the weather has been.  The following season, you should only have to water in periods where there is no significant rainfall for two or three weeks.
Some perennials prefer moist soils, and these will need water on an ongoing basis.  This is usually made fairly clear on the plant care tag.  Astilbe and Rogersia are two such examples; they may need water two or three times a week depending on soil type and amount of sun the receive.
 Trees should be watered deeply every two to three days for the first week, depending on conditions.  For the remainder of the month, twice a week should be an ample amount of water unless the weather is extremely hot and/or windy.  Decrease to once a week until the weather is cool and there are frequent, heavier rains.  It can be harder to tell if you’re watering your tree appropriately, and usually the best way to find out is to dig about two inches into the soil near the rootball.  If the soil is nice and moist there, then you are probably giving it enough water.
As with perennials, there are some trees that do best with frequent watering.  Birch is a great example of a tree that you should be watering weekly all season to maintain optimum health.

Do I Water If It Rains?
A good, steady drizzle is great for plants.  They get a nice deep watering, a break from the sun, and a small amount of fertilizer all at the same time.  A moderately heavy rain will also likely replace your watering for the day.  But rain events can be deceiving.  It can appear to you and I that it rained a lot, but the soil dries out quickly.  Sometimes a heavy rain can just run off, and only the top half inch of soil gets wet.  It may sprinkle here and there for a few days, but it’s overcast and the air is muggy, so the soil stays moist.  Try to be aware of how much rain is actually falling, and how your soil handles moisture, and you’ll be better able to judge whether or not you still need to water.

 Problem Situations:

 It is often said in gardening circles that 90% of plant fatalities are due to overwatering.  While we don’t have any statistics to support this, we see quite a few drowned plants every year. Most commonly, people notice brown, soft areas on the edges of the leaves, and the leaves are just slightly wilted.  This is the point where your might wonder if your plant needs water, and give it a little drink, just in case.  If this pattern continues, you may find that your whole plant is wilted, leaves that weren’t brown before are now yellow, and the leaves are dropping fast.  The remedy is to let the plant dry out, but not too much.  Excessive dryness following excessive moisture will further shock the plant and may kill it.  In dire cases, you may use a garden fork to loosen the soil around the roots to improve airflow and drainage, but remember that damaging the roots may exacerbate the plants’ condition.
Shallow Watering:
This condition is variation on overwatering in which the soil around the plant is given a little spray every day or two.  This teaches the roots to stay near the surface where the water is, instead of delving deeper into the soil as they would with a heavy, prolonged watering.  The plant then relies solely on your daily attention, so if you are away for a few days, they suffer and may die.  The other problem with this approach is that the shallow root system is much more susceptible to extreme summer and winter temperatures, as well as the freeze-thaw cycles during the winter.  This is often the cause of winter kill.

This problem is easier to identify:  brown and crispy leaf edges.  If the lack of water continues, leaves will turn brown and drop, and twigs and stems will begin to get crispy and die back.  The best solution is to water the plant, and this will usually lead to a good recovery.  However, be careful not to tip the scale in the other direction with overly frequent, heavy watering!
 These general guidelines should solve watering woes for many of you! However, we do understand that there is a broad range of soil types and microclimates here in Southwest Ontario, and not everything will work in every situation.  If you need more than general advice or have questions about your specific situation, please give us a call or send us an email; we’re always happy to help!

Happy Watering!

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