As the full force of summer arrives, and high temperatures are already being recorded across the country, it is time to think about protecting our plants from drought. With unlimited water and time, or automatic irrigation, it is of course no problem, but many people are making the decision to reduce their garden water usage, either by choice, because of rising water costs, or because more and more cities are placing restrictions on watering your garden, either permanently, or seasonally, which usually means exactly when your plants need it most.
While Thuja Green Giant is not a true ‘xeric’ plant, it does have considerable ability to resist seasonal drought, at least, when it is well established. So the first order of business in making your screens, hedges and specimens of this fabulous evergreen drought-proof is to establish it well. After that we need to conserve the moisture already in the soil, and when we do need to water, make sure we use as little as possible, and get it where it can do the best job of keeping your plants alive. Let’s look at those things in turn.
Establishing Thuja Green Giant for Drought Resistance
Moisture levels in soil increase as we go down, until very often we reach a level where ground water is permanent, and there is abundant water available. In practice that is usually too far down for tree roots to reach, but every few inches deeper means more water, so the first step in making your plants drought-proof is to make their roots spread as deeply as possible. As well, a larger volume of soil from the surface down will make it easier for your plants to find enough water.
Deep Soil Preparation
This is the key, and it means a little extra work when preparing your planting site. Although you may be spacing your plants 5, 6, 7, or 8 feet apart, digging small individual holes is not ideal. A much better approach is to create a broad strip of prepared soil the whole length of your planting, as this exposes a much greater soil volume for your plants to penetrate. Run a string along the route of your hedge or screen, making sure it is 4 to 6 feet inside your property line, and then mark it a minimum of 3 feet wide. If you can, wider is even better. That whole strip should be deeply dug, either by hand to the full depth of a full-sized spade, or by rototiller.
If you use a rototiller, one quick run along the area is not enough (sorry!). It might look great, but that beauty is only ‘skin deep’, and almost certainly you have only tilled a few inches down – stick a spade in if you don’t believe it. Ideally you should pass along the area two or three times, as slowly as possible, and holding the machine back so that it digs deep. By the time you are finished the digging tines should be invisible, and deep in the ground.
Add Organic Material
Besides its nutrient properties, organic material (garden compost, animal manure, rotted leaves, etc.) is a great water-retainer. By adding it to your soil you increase the water-holding capacity greatly, without reducing air penetration, so the roots remain healthy. Remarkably, this is true of both sandy soils, where it seems obvious, and heavy clay soils, which we (wrongly) figure have lots of water in them. [Because they are so fine, clay soils don’t release a lot of the water in them – it remains trapped and unavailable to plants.] So spread a layer several inches thick across the planting area and till it in – it will really make a difference in every soil.
Water to Encourage Deep Rooting
Once planted, your new Thuja Green Giant plants need to spread their roots wide and deep, so they can access as much water as possible in future dry periods. This means watering the right way, to encourage that. At first, for perhaps the first month, the water needs of your new plants must be supplied from the roots in the root ball that was inside the pot – that is all it has. This means watering close to the stem of the plant is essential, and if the weather is hot this might be needed every 3 days. In ordinary spring and fall weather, do it weekly.
As well, we want to encourage those roots to move out from that small volume, and to spread into the surrounding soil you have carefully prepared. They won’t do that if the soil is dry, so you also need to water over a larger area than just where the root ball is. After that first month, avoid watering close to the stem, and focus on deep, weekly watering of a wide band of soil around each plant, or ideally, along the whole row. Get those roots moving out!
Maintaining Established Thuja Green Giant during Drought
Once your plants have spent that first season getting established, we now want to keep those roots spreading, but as we said earlier, getting water to them can be tricky, so we want to encourage independence and conserve what is already there.
The classic way to conserve moisture in soil is with mulch. Any material, from plastic to paper, bark or gravel, that we lay over the soil will conserve moisture by reducing its loss from the surface. Yes, if you don’t mind the look, spreading out the local paper, or the Sunday New York Times, over the ground, and holding it down with a few rocks or some scattered earth, is a great short-term mulch. Even better is a 2-inch layer of that rich organic material you used to prepare the ground. That really is a better choice than bark, shredded wood, or stones, although cost is a significant consideration too. Rich material will rot down in two or three years and need replacing, but it will also fertilize your plants and maintain the water-holding capacity of your soil, so it is a much better choice.
If you don’t want to, or can’t mulch, then keeping the soil cultivated actually conserve moisture. The surface dries, but the broken up soil doesn’t draw much water from deeper down, and acts as a ‘soil mulch’ – it’s a useful tip, as well as keeping your planting looking great and weed-free.
Keep All the Water You Apply
If you have done things right, watering should be a last resort, and only needed during extended dry periods. Even if your plants look sad, if they are well-established, they will stay alive and come back when you can water again. If water restrictions are not in place, the simplest and most obvious way to water your plants is to grab the hose and start squirting, right? In fact, that is the worst way to do it. Large amounts of water evaporate before it reaches the ground – and the finer the spray the more you lose. So you pay for water your plants never even see. As well, you damage the soil surface, compacting the ground and drawing water more rapidly to the surface where it evaporates. (Mulch will of course prevent that compaction, another plus for doing it.)
Much better is to let water trickle gently into the soil from a slow-running hose. It will spread sideways too as the soil becomes wet, although not so much on very sandy soil. Even better is to weave a soaker hose (shown above) in and out through your hedge, as it will gently spread water over a large area, and this method uses a lot less water that standing there with a hosepipe!