Still the most popular hedging and screening plant around, Thuja Green Giant really gives its best in your garden. For a reliable, fast-growing and tough hedge, it can’t be beaten. When you have made the decision to plant this terrific evergreen, then timing is important, and the question of when is the best time of year often comes up from beginner gardeners.

With plants growing in pots, it is possible to plant any time the ground is not frozen, and deciding when may not be a matter of choice – you need that hedge, and you need it now. The availability of potted plants makes that possible, None the less, there are good times, and not-so-good times to plant. The middle of summer, with its heat and dryness, is probably the worst time, as you will need to be watering almost constantly, and root-growth into the surrounding soil will be minimal. As for the best time, there is really no doubt, it is early fall. Let’s see why that is.

The Soil is Warm and Moist

We often say that when it comes to plants, ‘it’s the soil, stupid!’ With fall planting, that is certainly true. Fall often begins with an extended period of rain, and falling onto soil that is hot from the summer, the result is moist, warm soil – ideal for the growth of roots. Contrast that with spring planting, when the soil is cold and wet. If you live in areas where the frost goes deep into the ground, you might even have frozen layers still below the surface in spring, so you are effectively planting onto an ice pack. In that environment, water moves slowly, and there is little oxygen in the soil. Dangerous microbes thrive in these low-oxygen conditions, and they can attack the young roots of your Thuja Green Giant, setting up a struggle for survival that certainly slows down the establishment of your plants.

In that warm, moist fall ground, good microbes are active, releasing nutrients, and protecting your plants. The roots divide and divide rapidly, and if you have prepared the ground well, they quickly penetrate deep into the ground.

The Air is Cool

In contrast, the air temperatures of fall are low, especially at night, and it is a fact that the roots of your Thuja Green Giant grow well in temperatures that would stop the top growth all together. The top is prevented from growing by the cool air, so all the energy of the plant goes into establishing a wide and deep root system.

In spring the opposite is true. Then the ground is so cold that even roots don’t want to grow, yet the warm days stimulate new shoots. It is easy to make the mistake of thinking that rapid growth of new leaves means your plant is doing well. If it is newly-planted, that may not really be true. Sooner or later the roots will have to catch up, or the top growth will suffer. If you have a spring heat-wave and drought, something that is common, then it is easy for the roots to dry out, fail to supply the leaves with enough water, and we see die-back. At the very least, you will have a lot of work keeping your new hedge watered. In fall, those first rains are almost always followed by more, so a steady moist soil is yours, with no work needed.

There is Plenty of Time

The most common cause of poor establishment in spring is the rapid arrival of summer. Spring planting is often a narrow window, between frozen ground and summer drought. Spring flowers know that – which is why they burst out of the ground and flower so quickly. There is no time to spare. If you are a bit late in planting, or summer comes early, then your plants are not established, and you are facing a summer of endless watering, not what you want at all.

In fall, we are pretty much guaranteed a couple of months of mild, damp weather. This gives your plants plenty of time to establish their roots, without facing drought or heat. Obviously a much better situation for good establishment.

What about Winter?

At this point somebody will be thinking, “But won’t my plants suffer in winter, if I plant them in fall?” This is a common idea, but one that is not true. If you live in a zone where Thuja Green Giant has no problem with winter (which would be zone 5), then neither will young plants. The earlier in fall you plant, the better – September beats November, without a doubt. The secret is to allow enough time for the roots to spread out and establish themselves, before soil temperatures get close to freezing, and root growth stops. But you have a big window, depending on where exactly you are – certainly from Labor Day to mid-October, and usually all the way to Halloween. Just a few weeks, under these ideal conditions for root growth, is all it takes.

If you do find yourself delayed, and don’t plant until close to freeze-up, then spray your plants with an anti-desiccant coating, just to be sure. These treatments are excellent for evergreens, and they protect from winter-burn very effectively. Use them even on established evergreens if you want to see perfect green in spring, particularly in colder regions.

Ready for Spring

The greatest thing of all about fall planting is that by spring, your plants will be ready to take off – and put on lots of strong new growth. They will have the root-development to support vigorous stem extension and a dramatic increase in height.

Thuja Green Giants that are well-established when spring arrives can take advantage of the season to really get going, and they will take the summer much better too. You can pretty much guarantee that the same size plants, one batch planted in September, and the other in April, will not make the same growth. By the end of their first summer the ones planted in fall will be significantly taller and bushier than their spring-planted equals. It is from plants such as these that the measurements of over 3 feet in growth a year are taken. Fall planted, well-established by spring, and fertilized and watered as needed.

Save Money Too

Oh, there is one more thing. Nurseries often put their plants on sale in fall. So there are really substantial savings to be had. Plus, many sellers offer free shipping. As well, the plants you receive have already had a season being cared for by the nursery, so they are solidly the height advertised, and you get an extra ‘growth bonus’ too.


Taken together, all these factors tell us that fall planting of Thuja Green Giant is the way to go. If you are planning a hedge, but thought you would wait till spring, think again, get your order in, and plant in fall. You won’t regret it.