Heading into another toasty Ottawa weekend (if it is Canada Day, it must either be roasting or soggy with massive downpours…), a very important question comes to mind for gardeners heading off on a camping trip or just the water conscious at home: do I need to water my native plants? After all, part of the reason to go native in the garden, as it were, is to reduce the amount of work tending a traditional ornamental garden requires.
At the FWG we have a sprinkler that we turn on as the baby plants in the nursery require since they can dry out more quickly in their small pots. There is an automatic sprinkler for the grass in the Backyard Garden since its more high-traffic nature means wear and tear is more obvious and damaging with very dry grass. We don’t water the plants in the BYG or anywhere else at the FWG unless they are newly planted and becoming established.
In the BYG we use water from a rain barrel for transplants. We have a portable tank in the Butterfly Meadow where the water is used sparingly and only for new plantings. It does get refilled as rain isn’t sufficient for the BM’s needs – especially as some visitors saw fit to keep opening the tap and letting the whole tank drain. We hope that we have now found a way to prevent that with a removable handle, but time will tell.
In the ravine we do water our newly planted trees from the hose, as there is no other source in the area. In fact, we sometimes have to lug big buckets of water along the slope since the hose doesn’t stretch! A good soaking once a week if there is no rain, or every two weeks depending on precipitation is a good rule of thumb.
As you can no doubt determine from our watering approach, you DO need to water your native plants under certain circumstances. New plants should be regularly watered at least once a week in the garden for the first several months as their root systems become established. Be sure to always water a plant right after putting it in the ground. This year was cooperative with a lot of rain in later spring, so those plants in our garden are now well-established and no longer require watering.
Some plants which are accustomed to much drier conditions, such as Prairie Smoke, don’t necessarily need to be watered so frequently. Just look at what the plant is telling you – wilted leaves and yellowing can be a sign of over or under-watering. Drying leaves is a sure sign of under-watering!
A good soaking occasionally is better than frequent sprinkles, and the common suggestion is allowing two inches of water to fall on the plant’s root area. To learn how much water this is, simply place an empty can beside the plant as you water, and you can quickly learn how much volume of water is displaced from your watering bucket to be equivalent of two inches depth.
New trees and shrubs are water hungry and should be watered at least once a week. It is possible to buy water bags which attach around the base of the trunk and which slowly release water into the soil. They are unsightly, but an acceptable alternative especially if going away on vacation!
The second scenario where watering may be required is with plants that prefer wetter conditions, such as Boneset or Marsh Marigold. Many of these plants will grow just as happily in lower-moisture conditions, but some marsh plants do require supplemental watering if dry-stretches occur over longer periods of time. Let the plant tell you if it needs additional moisture by observing it for tell-tale signs such as drooping over repeated days or leaves drying out and crisping.
Of course, if it rains you can omit watering – provided that the rain is sufficient to soak the soil well. A rain gauge is an excellent tool for deciding whether you should supplement with additional moisture.
So, the lesson today is that you DO need to water your native plants unless they are established in habitats that provide them with the correct level of soil moisture. Thankfully, the latter scenario is almost universally the case!
Tips for Using Less Water in the Garden
1) Use native plants adapted to your soil conditions.
Any plants we sell at the Plant Sale have their ideal soil moisture requirements listed on the inventory list. Usually, plants can be fairly flexible and tolerate a wider range of soil moisture regimes. However, don’t expect a dry-soil loving Nodding Onion to thrive in the same soggy soil as Cardinal Flower and vice versa! Plan your garden according to what you can grow with the least effort.
2) Mulching around trees and plants can help retain moisture.
Don’t mulch too thickly so that no water can penetrate from above, and don’t mulch too thinly such that there is no barrier to quick evaporation. In general, one inch deep of mulch is plenty for herbaceous plants and up to two inches for trees and shrubs. Use natural mulch like leaves or wood chips. Don’t use wood chips that are artificially dyed or chemically treated.
3) Buy a rain gauge to measure how much moisture your soil is receiving.
With light rains the soil barely becomes soaked, and with heavy rains much of the water just runs off after the first minute as it cannot infiltrate into the ground so quickly. Use the rain gauge as a guide, and consider the pattern of rain fall. The best rain fall for gardens is slow and steady. Soil moisture metres are a lot more expensive, but much more accurate.
4) Buy a rain barrel with a good mosquito screen.
If you can connect your downspout to a rain barrel you are best able to take advantage of the water savings afforded by this device. More water will enter your barrel this way than if it were just to enter free fall (think of an open bucket – the surface area of the bucket opening is much smaller, so more water must enter before it fills – unlike the large area on the roof of a house which is designed to move water away and into drainage pipes). You can run a hose from the barrel, but unless the barrel is full, water pressure will be negligible. Lastly, you can always fill your bucket or watering can and carry it around. There are usually rebate programmes in the spring for buying rain barrels, and they come in all sizes and designs.
5) Let the plant tell you when it is thirsty.
Plants will naturally droop and look parched during the hottest part of the day as a survival mechanism due to high transpiration rates. Next time we have three days of above 30ºC weather, monitor the leaves of a lilac tree standing in full sun – you’ll notice the leaves appear limp in the afternoon, but will rebound by mid-evening! Observe your plant in the early morning or in the mid-evening when it is not under solar stress in order to determine if it really needs additional moisture outside of your watering time-table – or if you even need to water that week at all.