Growing Small Trees in Containers

I’ve been thinking a lot about containers for small trees lately. I am re-designing a garden for a client, adding more permanent color since there is a heavy reliance on annuals for color right now. While clearing out the heavily overgrown mixed shrub borders, we found a forgotten peegee hydrangea tree.

Peegee hydrangea planted improperly

The rootball of the peegee...planting improperly about 5 years ago, the roots are a tangled mess.

Planted improperly years ago and then slowly obscured by its faster-growing neighbors, this small tree should be a specimen tree, planted in a place of honor where it’s beautiful lines and massive summer flowers can be appreciated. But, there’s simply no place to put it.  There are already two other peegees on the property so  ‘finding’ a place for this forgotten one is a little more difficult than it should be.

Rather than give up on it, we decided to plant the peegee hydrangea tree in a large container and place it on one of the patios. Using small trees in containers on a terrace, patio or deck is a great way to bring your garden up close and personal. Many people use containers for annuals but don’t consider planting larger, more permanent plants, like trees and shrubs, in them.

 

Choosing Containers for Small Trees

Square container for peegee hydrangea tree

My client decided on the big square container on the bottom for her peegee hydragea.

Think BIG ~ We’re using a 25” square container. If in doubt, buy the next larger size. Woody plants have larger roots systems than annuals and perennials so they’ll appreciate the extra space. And the extra soil will act as an insulator once the temps really drop.

Consider the Weather ~ In cold climates, like here in Connecticut, you need to choose a container made from a weather-resistant material. Fiberglass, stone, wood and metal are popular winter-proof choices. Our container is made from a lightweight polyethylene that looks like lead. Terra cotta pots, even glazed ones, are too porous for outside use in winter. Water gets into the material, freezes and eventually the terra cotta cracks.

Improvise ~ A great way to put your stamp on your garden is to re-purpose items and make them into non-traditional containers. The possibilities are endless; just make sure you add drainage holes in the bottom.

 

Choosing Small Trees for Containers

Consider Your Zone ~ A good rule of thumb for choosing woody plants for use in containers in cold climates it to use a plant that is hardy to at least one zone (I prefer two) lower than your in-ground hardiness zone. My client’s garden is a zone 6B or even zone 7, so using a peegee hydrangea that is hardy to zone 3 is a good choice.

Thuja plicata 'Whipcord'

This whipcord arborvitae is just one example of a conifer that's ideal for a container. Eventually, it will be 5' tall but right now it's only about 1' tall.

Long-term Strategy  ~ Think about your long-term strategy for the plant you will using in your container. If you’re planning on growing your small tree for years in the container then choose a tree that will not outgrow the space. A small tree that matures around 15′ tall is probably a safe choice.

Another strategy is to grow young, small trees in containers for a few years until they are large enough to make an impact in the garden. This can be an especially useful strategy for expensive or slow-growing trees like conifers. Many conifers are costly and grow just inches per year. You can save some money by purchasing a smaller size, growing it in a container for several years and then planting it in your garden once it’s a bigger.

Are you growing small trees in containers? If so, I’d love to hear which ones you’re using.

13 thoughts on “Growing Small Trees in Containers

  1. What a fantastic post. I have been struggling with growing a tree in a container and I now realize I am trying to grow a tree that is in my zone and not 2 zones lower. That makes so much sense. And I love PeeGee. I think I may just have to try this in the spring…I have just the right container too…

  2. Great advice! Have you found that the roots need to be trimmed over time? Maybe if it is a small enough tree, it would be easier to lift it from the container to trim roots and promote new root growth. I have also seen wooden containers with removable sides for this purpose.

    • Hi Matt, Root pruning hasn’t been an issue yet but I imagine it will be at some point. I like the idea of removable sides, I’m sure that comes in handy for several chores.

  3. I have a Carpenteria Californica ‘Elizabeth’ in its second year. It is actually 1 zone higher, but whenever a freeze threatens I wrap it up in its heavy terra cotta pot (guess I am bucking the rules on at least two fronts). It has grown nicely, but did not bloom last summer. I think it may be a candidate for going into the ground next spring. The other small tree that has lived happily in a pot for about six years is Enkianthus campanulus ‘Red Bells’. It is in a plastic pot that passes for terra cotta as long as you don’t look too closely. Thanks for this post: it points me in the right direction.

    • Ricki, Don’t you just love it when things work out, even when they’re not supposed to? I bet the Enkianthus is fantasist in a container so you can see and smell it’s delicate flowers up close.

  4. I have a potted fig tree and two tropical hydrangea that live outside during Connecticut’s frost free months and inside other times. But for cold hardy trees I’ve only tried growing two dwarf Alberta spruce (Picea glauca ‘Jean’s Dilly’). They did quite well in insulated pots on a south-facing porch from late summer through the following spring, then their needles slowly started turning brown and they eventually died, even though I was very careful to not over or under water them.

    I chickened out trying to overwinter two small boxwood in pots on the same porch … figured I’d rather have them in the ground and alive than on the porch and eventually dead.

    I may try other small conifers in pots, if I find two I really like at a decent price.
    I’ve had luck growing a hardy kiwi vine (male only) in a large plastic pot. It remains outside year round.

    The idea of a potted peegee hydrangea intrigues me, especially after losing my in-ground one to TS Irene. I’ll let you know if I try the potted route next spring.

    • Joene, I’ve had several small conifers in containers for several years. So far they have defied the odds – planted in containers that are too small and completely freeze during Jan & Feb, the little guys just seem to hunker down and bide their time until Spring. I actually planted them in the ground a few weeks ago since I think the containers were stunting their growth. I hope I don’t have the opposite luck that you have!

  5. Hi…
    I have found for wintering potted containers {here in NE Wisconsin near Green Bay (ZONE 4) } that wrapping several layers of bubble wrap around my pots works. Then I try to group the containers together and surround them (containers) with bales of marsh hay to offer more root protection. The buds are winter hardy but above ground is harsh for the root systems. I have some ZONE 5 ‘s that winter well this way. Also getting them moved to a location out of the prevailing winter winds helps.

    • Kathy, The bubble wrap is a great, inexpensive idea. It seems like over the past few years, for various reasons, we’ve had lots of plants out of the ground during the winter (this year it will be because of winter tree work so we’re moving shrubs that are directly under some trees) and we typically bunch the container together, as you mentioned, and then insulate the entire mass with leaves. Thanks for stopping by and leaving a comment.

  6. Hi, this article was very informative, Thank You. I still have some questions though, I live in Wyoming, where it can get very cold and scary windy, I just put 2 pink diamond hydrandgeas in very large pots, they are pruned like topiary trees, and I also have a very small laceleaf Japanese maple that is in a pot. My question is if I bring these guys indoors for the winter would they still grow with ample light, or do they need to lose all there leaves and go dormant for the winter months?

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