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How to keep container plants happy

At my new address, my gardens are a work in progress. For immediate gratification, I also create container gardens.

Windowboxes, hanging baskets and other planters are wonderful if you have limited space, not a lot of time to work in a garden, or health and mobility issues—they can be worked on at a comfortable level without having to bend down a great deal. There is (usually) little or no weeding; and you can grow a huge variety of plants, from herbs and some vegetables, to flowering shrubs, perennials, annuals, tropicals—the combinations are endless.

They are especially ideal for planting at a cottage where you might only visit on weekends, provided you follow a few tips for care; and a great solution if you have wildlife visitors in your ground-level gardens; unless, of course your wildlife is brazen enough to come up on your deck.

Here are guidelines to keep container plants happy.

Containers

You can use pretty much anything for a container providing it has holes drilled in it for drainage. The larger the container, the more room there is for roots to develop, and the soil won’t dry out as quickly as with small baskets or boxes—but large containers are heavy and require much more soil.

If you want to use a container that doesn’t have drainage, create your design in a slightly smaller pot with drainage holes, and set that in the bigger pot. Bear in mind that after a heavy rainfall you may need to tip the smaller pot to drain it of water, lest roots rot in too-soggy soil.

Potting medium

Use one of the good soilless mixes available at nurseries (ask for professional grade for best results), rather than garden soil, which is heavy, possibly full of weed seeds and plant pathogens, and has questionable nutrient levels.

Fertilizer

Don’t bother purchasing potting mix that include chemical fertilizer and “water retaining” compounds. A better option is to add compost, worm castings or other organic fertilizer to your potting mixture, and to fertilize weekly with a compost tea or liquid seaweed fertilizer such as SeaBoost.

Plants

Selecting plants for your containers is the best part, of course! If you want flowering plants, choose something with a long period of bloom, unless you are going to have a multitude of planters and can vary up your choices. (See sidebar for some great suggestions.) Most of us use annuals in our windowboxes and other planters, but you can also add smaller perennials, especially foliage stars such as heucheras and hostas, or compact forms of ornamental grasses.

If you’re interested in growing a few vegetables, there are some that will do very well in containers, such as salad green mixes, radishes, beets, Swiss chard, compact types of peas, the so-called patio tomatoes, and many types of herbs.

Continuing care

For flowering plants, fertilizing once a week is important to keep encouraging blooms, but it is also important to deadhead your plants, removing spent flowers, especially from annuals. Annuals are programmed to germinate, flower, set seed and die in one growing season, and if they start to produce seed, they may stop flowering.

It’s also a good idea to pinch or shear back annual plants to encourage bushiness and more flowering stems. You do this by cutting one third of the plant back by one third of its height every week, over a three-week cycle.

Water, of course, is vital to plant survival, and if you’re away during the week and only see your containers on weekends, they might dry out. This is where having large planters is particularly helpful, because they hold more soil and thus more moisture. You can make a simple gravity fed watering device by cutting the bottom out of a 2-litre plastic pop bottle, filling it with water and inverting it into the soil of your container. The water will disperse gradually as needed, and bottles can be refilled by hose or rainfall. Grouping containers together can help to reduce evaporation, too.

Another option for gardeners who want container gardens at the cottage is to plant fleshy leaf succulents such as hens and chicks, ice plants and sedums—because they naturally retain water they require less watering than many plants. They may have colourful foliage as well as unusual flowers, and can be planted out in small, shallow containers.

Great plants for containers

While petunias, marigolds, pansies and geraniums are faithful staples of container plantings, there are so many more options for flowering plants—with more being developed all the time. Here are 15 good candidates to keep in mind.

  1. Anagallis: Blue Pimpernel has a sprawling habit and deep, cobalt blue flowers.
  2. Agastache: Hummingbird mint is a real magnet for pollinators of all kinds.
  3. Bacopa: Instead of annual lobelia, which dislikes summer heat, try bacopa, with a trailing habit and white, pink or lavender flowers.
  4. Bulbs: Try summer bulbs such as dahlia, dwarf lilies and alliums, begonias and gladiolus.
  5. Chocolate cosmos: This tuberous annual has deep wine flowers… that smell of chocolate.
  6. Coleus: These shade tolerant foliage plants offer dazzling colours and different leaf shapes and sizes.
  7. Fuchsia: Popular for hanging baskets, the elegant, drooping flowers of fuchsia are attractive to bees and hummingbirds; also shade tolerant.
  8. Heliotrope: Highly fragrant purple or white flowers attract pollinators, and delight humans.
  9. Heuchera: Coral bells are perennial and can be planted in the garden at season’s end. Colourful foliage and sprays of flowers attractive to hummingbirds.
  10. Grasses: Annual millets, bunny tails (Pennisetum), various sedges (Carex) and perennial Japanese forest grass (Hakonechloa) add great texture and late-season interest to containers. Many are drought tolerant.
  11. Lantana: Though it smells unpleasant to humans, this colourful annual is coveted by butterflies.
  12. Nemesia: A long-blooming annual with a range of colours. Some varieties are fragrant.
  13. Osteospermum: African daisies bloom until a killing frost, especially when deadheaded regularly.
  14. Succulents: Annual and perennial ice plant, portulaca and purslane, sempervivums, echeverias, aeoniums and sedums are excellent drought-resistant choices.
  15. Sweet potato: Grown for their colourful foliage, these vines love hot weather.

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