5 tips to keep your outdoor container plants alive

Nothing adds a pop of color, a smidgen of style, or a dash of drama to the garden like a perfectly planned and planted container. And while every gardener has their magic recipe for what works (surprise, surprise!) it isn’t rocket science. Good containers, like just about anything else in life, take only a little attention to a few basic principles.

So since container planting season is rapidly approaching, here are my five steps to success:

Why you should use big containers for your container plants

I’ve been there, and I think you have been, too. It’s springtime so you pick up one of those perfectly coiffed, 8-inch or 10-inch diameter hanging baskets of petunias. You proudly bring it home, hang it in a nice, sunny spot, and give it a nice drink of water. All’s good so far.

The problem is, that’s about as good as it gets. As the weather warms and the days turn into weeks, your former shining star of a hanging plant starts the inevitable march backward. In no time, it ends up on the compost pile.

The problem isn’t you. Not directly, anyway. The problem is that by the time you brought the basket home from the store, the plant was probably already too big for its pot. And once you hit that stage with a heavy-feeding plant (as most annuals are) you can’t win.

Now I have no personal vendetta against the 10-inch hanging basket of annuals. It’s just that you have to keep in mind that those little plastic pots were never meant to hold the plant(s) for a full season.

In general, most people make the mistake of going with containers that are way too small for the intended planting. I have barely enough sun in my garden for a single tomato plant in a container. How big a container can I use for that one tomato plant? Thirty-six inches in diameter! And that one little tomato plant uses up every cubic inch of space by the end of the season.

If you’re looking for nice container plantings, I recommend 20 inches in diameter should be about the smallest container most people should consider.

What type of potting soil or planting mix should I use in my container plants?

OK, not so much the hole but what goes in the hole, aka planting mix. If you’re an experienced gardener, you probably already have a recipe. Mine revolves roughly around some pine fines with a little compost and whatever else I might have sitting around the yard. But if you’re starting out, or you’ve had a bad year or two, do yourself a favor. Go out to the garden center and purchase a quality soilless planting mix.

Good mixes contain a wetting agent (ever try to wet an old bag of peat moss that’s been sitting in the garage for 3 years?), a nice starter charge of fertilizer, and a good balance of particle sizes to make sure they drain well. A good mix also has no mineral soil.

Side note: should you put gravel in the bottom of your pot? No. While the old myth holds that adding coarse gravel improves drainage at the bottom of your container, the truth is it does the opposite. The gravel (or broken pot shards) reduces the rooting volume available to the plant’s roots. The best practice is to use a good, well-drained mix and leave out the gravel.

How often should you fertilize your container plants?

Most annuals are tropical plants, and one thing common to many tropical plants is that they can be heavy feeders. If you skimp on the fertilizer they tend to end up puny, undersized, and with few blooms. But most container mixes don’t hold much in the way of nutrients. So, if you load a bunch of nutrients into your container, odds are most of them will end up leaching out of the pot and running down the driveway. Not a good recipe for the plant or the water systems in the area.

Constant, low-lever fertilization is best. Slow-release fertilizers release a tiny supply of nutrients every time you irrigate. That way there’s little to get leached away. If using soluble fertilizers, I recommend fertilizing more frequently and at a lower concentration than what is normally listed on the fertilizer bag.

How often should you water your container plants?

No surprise here, but water is the key to it all. One little bit of wilting one afternoon can mean your plant takes two or three full days to fully recover. And even once recovered, it has lost that time and is now behind where it would have been.

To help facilitate watering you can follow several strategies. Automatic watering systems are now a dime a dozen. Even my budget home security system has about a $39, wifi enabled water valve that can be operated from my cell phone. It can be scheduled or operated manually. Low water-requiring plants such as succulents, can also make watering easier. And a great practice to have in your quiver is the midseason cutback. When plants get a bit too big and are sucking up too much water, just trim them back. Most vigorous annuals will recover in a week or so.

Why you should skip containers with mixed plant types

One of the hardest things to master is a mixed container with three, four or five 5 different plant types. Sure, it’s easy to pull together something that looks great for the first few weeks. But as the season rolls on, there’s almost always a clear winner and a clear loser (or two or three.) If you want some variety, get four or five containers and plant a different type of plant in each container. You can then mix-and-match and rearrange as relative growth dictates — or as your mood changes.

Paul Cappiello is the executive director at Yew Dell Botanical Gardens, 6220 Old Lagrange Road, yewdellgardens.org.

GOODSEED FARM PHOTO You shouldn’t be stingy about filling large pots with good potting soil, and replacing it each year.