It is the green parts of plants that we see, and beneath the ground is often ignored. But for trees, that area is so important, as vital activities happen there. Successful growing should emphasize what we do with the root system, and if we do that, the upper parts will usually take care of themselves. Let’s see what we should be doing to care for the roots of our evergreens, to give us the fast and healthy growth we want to see.
Give them Room
We are (hopefully) going to consider how much room above ground our plants need. For example, Thuja Green Giant has a spread of as much as 12 feet, so it should not be planted closer than 6 feet away from walls, fences, property boundaries and foundations. Its root system takes up even more room, and although it will adapt to obstructions, growing around or underneath them, you cannot grow a full-sized tree in a very small volume of soil. So when planting around buildings, or between construction features like driveways and garden walls, consider if you have enough room. As well as your plant suffering, your construction can too, as large plants too close to retaining walls can weaken them and cause their collapse, and planting right alongside a walkway or drive can result in cracks and lifting developing in a short time.
For the best growth of your trees, creating a large volume of soil is essential, as often the ground is too hard for them to easily penetrate. This is especially true in newer properties, as heavy construction machinery will have been driven over the site, making the soil hard and unyielding. This problem is called ‘compaction’. Soil where you are planning to grow Thuja Green Giant, or other trees, should be dug or roto-tilled to loosen the soil. For a hedge a section at least 3 feet wide, and preferably wider, up to 6 feet, should be dug or tilled to a depth of 12 inches, or as deep as you can go. For individual plants, an area at least 3 feet in diameter should be prepared. This will separate the pieces, and even if your soil is poor, it will make it much easier for your young trees to spread out and down, finding water and nutrients over a large area, and so growing stronger and healthier. This is far better than planting into a small hole in hard soil, and then finding you have to water all the time and fertilize too, to keep your plants growing. The extra work of good soil preparation will be re-payed many times over with great growth and good health.
Enrich the Soil
No matter what type of soil you have, adding organic materials to it will improve it. In sandy soils, it helps retain moisture and provide nutrients, and in clay soils it improved drainage and air penetration into the soil. Suitable materials include garden compost; well-rotted animal manures like cow, sheep or horse; rotted leaves; spend mushroom compost; peat moss; or almost any other well-rotted organic material. Do not use woody material (such as wood chips) as these things rob the soil of nutrients as they decompose, and only years into the future do they feed your plants. Usually a layer 2 to 4 inches deep over the area is sufficient. Spread it over the surface and dig it in. If you are using a tiller, run over the area once, spread your organic material, and then till one or two more times. Mixed into the soil it will hold water for the roots, and as it rots down it creates drainage, and releases nutrients too.
Once you have finished planting and watering, then spread another layer 2 or 3 inches deep over the dug area. Keep it away from the stems of your trees, and don’t cover the low foliage close to the ground. This layer will act as mulch, conserving moisture. It will also prevent the growth of weeds, as these should not be allowed to grow up around your plants, especially when they are still young. As well, mulch of this kind, rather than bark chips or stones, will feed your plants too, as it rots down into the ground. Mulch should be renewed in spring for a couple of years at least after planting, and if your soil is very sandy, mulching each year is recommended. In richer soils it is not so necessary, and it may only need replacing every two or three years.
The soil is where your plants get water from, and even if your plants look healthy and green in dry soil, they are not growing. So watering is often necessary, especially when plants are young, and especially in sandy soils, and in hot places. New plants should be watered at least weekly during dry weather, even in the temperatures are not so high. Remember that newly-planted trees depend for a while on the root ball that was inside the pot, until they spread their roots outwards. So even if the soil looks damp, that root ball may have already dried out. Use a slow-running hose to trickle water down around the roots, rather than standing with a spray nozzle and squirting water about. Most of that will be wasted and simply evaporate into the air. This watering during the establishment phase is vital for your plants to get off to a flying start and put on lots of new growth for you.
In the longer term, putting in a trickle line will make watering easy. This can be connected to your irrigation system is you have one, or connected directly to a tap with a timer so that it comes on automatically, meaning less work for you.
Fertilize your Plants
New plants can take several years to develop an extensive root system. Without that they may not be able to access enough nutrients for maximum growth, even if you have enriched the soil. Today chemical and natural sources of fertilizer are available, so you can use which ever kind you prefer. The important thing for growing evergreens is that there is enough nitrogen in them for growing all those green shoots, especially if you are clipping, which removes the growth which then must be replaced. Look for fertilizers with a high first number in that set of three – it is the level of nitrogen. It should be close to 10 in a natural fertilizer, and close to 20 in a chemical one.
The simplest approach is to choose a blended fertilizer designed by experts for evergreens. Apply this a week after planting, unless you are planting in late fall or winter. If you are, wait until spring to fertilize, and in sandy soil or in the early years, a second feeding in mid-summer and another in early fall is beneficial, especially in warmer zones. In colder areas a spring and summer feeding should be enough.
With these steps – dig and enrich the soil, water regularly, and fertilize – you will see the best growth possible. It pays to focus on the ground if you want the best results in the air.