Where and When Should I Plant My New Tree?

Article #4 in the Series “So, You Want to Plant a Tree!”

Peter Duinker, Halifax Tree Project, 2023-05-26

The “when” of planting a tree is all about giving the new tree the best chance for survival. The “where” is also about survival, but probably more important is its role in preventing problems later in the tree’s life. Let’s start with the where.

A good location for a new tree on your property depends partly, perhaps largely, on the kind of tree you have chosen (and, of course, the tree you choose depends significantly on the location you have for the planting). Without going into the fine details of location for each tree species and each planting situation, I will list out some important considerations.

a/ Drainage – if you have a wet site, that’s OK, but you’ll need a tree that can handle wet conditions. If the site is well drained, pretty much any species will do.

b/ Sunlight – most tree species are fine to grow in direct sunlight. However, some are finicky about shade. Be sure to plant in a spot where, if you’ve chosen such a finicky species, the tree will get adequate sunshine.

c/ Soil – trees can grow in what seems like paltry soil, but you don’t want to stress the tree with too little soil. Choose a site that you predict has plenty of soil, especially depth. You could create a site with great soil, but that would be a considerable expense. Soil is so vital for both good anchorage and adequate root access to water and nutrients.

d/ Infrastructure – a little tree looks so small but, if things go well, depending on the species, it may become huge. And that’s not only the aerial parts – the root system becomes huge, too. It is not wise to plant a tree close to the built stuff – sidewalks, driveways, buildings, poles, high-tension wires, etc. And let’s not forget about underground infrastructure, particularly pipes and cables. It is not a good idea to plant a new tree right over top of your water and sewer lines, for example. In sum, if you have a favoured planting spot, just imagine a mature tree in that location – does the tree have enough room to thrive there?

e/ Ground vegetation – if you want to grow a flower or vegetable garden near the new tree, you are asking for trouble. Shade-loving plants may do well under it, but probably not sun-loving plants. And then there is the problem of allelopathy – some trees create conditions in the soil that are toxic to other plants – e.g., black walnut. I’m not saying that nothing will grow within the drip-line of the new tree, but be aware of the limitations a mature tree presents to ground vegetation.

f/ Competition from other trees – in nature, trees are used to growing near each other, even deeply intertwined with each other, even trees of different species. If you want your new tree to grow a perfect wide crown, then be sure to space it away from other trees. I’m actually a fan of growing trees closer together than many people are – I rather like to see the trees interacting. My rule is roughly as follows: for large-stature trees at maturity, a minimum distance of 4-5 metres apart would be a minimum. There are several rows of trees in the Halifax peninsula where the trees are this distance apart and they seem to be doing well in their later years.

I now turn to the question of when to plant a tree. To be blunt, spring and fall are the right times. You want to expose the tree to any trauma from transplanting either before or after the growing season. Planting is indeed a traumatic event for the little tree under all circumstances. So, given that the tree has to cope with a new environment and figure out the new circumstances, plant it either in spring – after the ground frost is gone – or in autumn after the growing season is over and it has hardened off, so to speak. For Halifax, I would advise a spring plant from late April to late June, and an autumn plant from mid-October to mid-December. The spring plant allows the tree to start a growing season in its new habitat, and a fall plant allows the tree to have become dormant and ready to lurch into spring when the appropriate temperatures arrive.

It is not the best, in my view, to plant trees in the period July through September. That means that the tree is halfway or more through its annual growth cycle at the time of planting, which puts a strain on the tree in the transition from where it was raised to the planting site. Moreover, it is my experience that we have our strongest droughts, generally speaking, in the summer months. Trees planted in summer in Halifax need especially consistent watering to get the roots going.