Potted Trees

Now that I live in an apartment, I find myself missing the fresh figs and nectarines, abundant almonds, and deluge of citrus from my old trees. And that got me thinking about putting a small fruit tree on my balcony. It ends up that you can grow a surprising number of fruit and nut trees in containers.

Even this bonsai Chinese quince can produce fruit! (Sage Ross) CC BY-SA 3.0

Following the same advice I gave in my post on container gardening, we’ll need to select a food-safe container with good drainage, fill the container with potting soil, and make sure the tree gets enough sunlight. But which trees can be grown in containers? And how big do the containers need to be? Let’s find out.

Tree containers and soil

Back in California, I had a friend who was growing an orange tree in a two-foot wooden planter box. The tree was 20 years old, less than three feet tall, and very productive. It can be done. The most important things to keep in mind when selecting a container for your tree are drainage, durability, and food safety. Too many planters out there are made of toxic materials. Make sure your tree’s home is made of food-grade materials and that there are drainage holes in the bottom of the pot. You’ll need a 10- to 15-gallon pot.

Tree roots can be surprisingly strong. I’m sure you’ve seen sidewalks that can attest to that. Your tree’s container needs to be durable enough to withstand tree roots and temperature extremes. Lightweight plastic may be easier to move around, but it probably won’t last as long as your tree.

Once you have a container, you’ll want to fill it with potting soil, not planting soil or topsoil. Topsoil may contain pests or diseases that may cause years of headaches and it won’t drain properly in a container. Planting soil is meant for the ground and doesn’t drain the way your potted tree will need. Potting soil is specifically engineered to help plants thrive in containers. And please don’t put rocks in the bottom of planting containers. All they do is take up space better allocated to soil and roots.

When you fill your container with potting soil, create a mound in the center of the pot. You will arrange the roots of your tree over that mound and then cover them with soil. Do not tamp down the soil. Instead, mud in your new tree to prevent damaging tender roots, making sure that the graft union is visible above the soil line. Remember that improper tree planting depth is one of the worst things you can do to your tree. Be sure to install a tree support until your baby tree has had a chance to send out supporting roots, then remove the support.

Which trees can be grown in pots?

Preparing for my trek across Spain, I saw this olive tree in Paris. Based on the trunk, I’d say it was a very old tree living in a rather small container. But it looks healthy, so you can certainly put olives on your list of possibilities.

Olive tree growing in Paris (Kate Russell)

Generally speaking, you will want to choose a dwarf variety tree. These are trees grafted onto M-9, M-26, M-27, or P-22 rootstock. Larger varieties will be okay in a container for a while, but they will need to go into the ground eventually. And transplanting a tree is no small feat. Which reminds me, containerized trees can live for 20 years or more. Because of this, it’s a good idea to have a plan in place for up-potting your tree, should that ever become necessary. Personally, I’m going to start with a full-sized container so that I can avoid that Herculean task.

There are several dwarf fruit and trees that can be grown in containers:

• Almonds
• Avocados
• Bananas
• Cashews
• Chestnuts
• Citrus--lemons, limes, Mandarins, oranges
• Figs
• Hazelnuts
• Macadamia nuts
• Olives
• Pecans
• Pomegranates
• Pomes--apples, Asian pears, pears
• Stone fruits--apricots, cherries, nectarines, peaches, and plums
• Walnuts

Potted orange tree (Dieter_G) Pixabay

To get the most out of your containerized fruit tree, you may want to get a fruit cocktail tree. These are trees that have different types of fruit grafted onto the branches. For example, a fruit cocktail stone fruit tree can produce apricots, nectarines, and peaches on the same tree. Or, you may select a 4-in-1 cherry tree with four different varieties of cherries growing on the same tree. It really helps make the most out of small spaces.

When shopping for rootstock, look for self-fruiting varieties, or you’ll need more than one tree to get fruit. Whichever tree you select, make sure that it is suited to your USDA Hardiness Zone. If you absolutely must have that dwarf lime (Zones 9-10) and you live in Grand Rapids, Minnesota (Zone 3a), you’ll have to bring it indoors for the winter, so make sure you have a plant stand with sturdy wheels. Or, you can keep it indoors and hand-pollinate. In either case, your potted fruit or nut tree will need at least 6 hours of sunlight each day.

Other factors to consider when selecting your potted tree are chill hours and local pests and diseases. One of the first things I noticed about Seattle when I arrived last summer was the number of plants affected by powdery mildew. And the few plants I put on my balcony were soon populated with stink bugs. (And I’m on the 7th floor!). Fruiting trees need a certain number of chill hours each winter to trigger fruit production in spring. As always, be sure to buy certified pest- and disease-free rootstock.

Caring for potted trees

Containerized plants need to be monitored regularly to make sure they don’t dry out too much in summer. You can encourage root growth by watering your potted tree from the bottom, rather than the top. Simply add water to the tray under your pot. The soil will absorb the water and the tree roots will extend downward to access that water. You will also need to feed your tree regularly.

So which tree am I going to get?

My balcony faces north and I live in Hardiness Zone 8b. Luckily, my balcony gets lots of sunlight and Seattle usually gets 3,000 chill hours each winter. My next step is to figure out which tree is least likely to attract or be affected by powdery mildew or stink bugs.

I found a website dedicated to thwarting invasive brown marmorated stink bugs (Stop BMSB) and learned that these pests love almond, apple, apricot, black walnut, cherry, fig, hazelnut, olive, peach, pear, pecan, and pistachio trees. They also feed on beans, cabbage, cayenne peppers, collards, cucumbers, horseradish, persimmons, soybeans, summer squash, sunflowers, and Swiss chard. Darn! It looks like my balcony garden is going to have a stink bug problem no matter what I grow! Luckily, fruit trees are mostly resistant to powdery mildew.

Based on where I live, the amount of sun exposure available, and all the rest, I think I am going to opt for a dwarf multi-variety cherry or plum tree for my balcony. Now if I could only find one that isn’t already sold out! Which tree are you going to plant?