The lesson on plant spacing is something you typically learn by doing it wrong. When the shrub arrive, you plant it too far from another one because you think they’ll have some space to breathe. You’re an optimist and you wait while they grow. Next year, there will be a big gap. Year after year, still nothing but empty space. Why? Because when you imagined it growing, you saw only the plant in that pot. But you didn’t picture what it might be like grown up…in the wild.
How much space does each shrub require? Plan ahead before you dig; the chart is above. It measures center-to-center distance between one shrub and another. No guessing here, geometrical knowledge. Know your plants. Mark their centers (not the outer edge of the root ball) so you know where they go. The trunk stay in one place. Leaves may come and go, seasonally, but the trunk remains stationary. There is no tangle, just a clean border.
How to Space Your Plants
With a hedge, however, it’s a different story. You don’t want one shrub here or there; you want a solid mass. And you know it’ll take some time to fill in. Most deciduous shrubs is planted about two-thirds the distance from where they will be wide… Wide enough to have their branches touch and tangle together within a couple of years. This keeps the plant healthy without letting the roots compete too much with each other. Too far apart and you’ll be waiting a decade for any privacy. Too close, and the middle will die out and get mildewy.
Remember, a formal hedge is different than a blooming screen: Dwarf boxwoods can be planted closely, sometimes a foot apart… And then trimmed to form a straight line. Close spacing is fine, since the hedge won’t have any branches to try to support or any flowers to open anyway.
But those flowering species (lilacs, forsythia) require air and light so they can grows from their inner buds. See the chart for how much more space flowering types need? That gives them room to display there springtime show without being a mass wall with no blooms.
And then there’s growth rate: Yew takes longer than privet (seven-plus years vs. Three). Ditto English boxwood. Most of us underestimate that time frame, it should of been easier to remember. In the second year, we look at the gap and freak out. Fight the impulse to fill it with something else now. Yes, that empty spot will be temporary, but you want that healthy screen. In five years, an excess of things will equal a crowded, unhealthy hedge.
There is another rule for specimen plants. Those are the stars: the plants you love so much, such as the hydrangea. These are the ones that gets to be just themselves. You don’t cut them back. Give them their space, all of what they will be when mature, and their width. Treat them as individual being. It’s easy; too bad we forget the rule on planting day. Measure twice, mark center, trust the math. Your garden will thank you for the room.