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Keep container gardens thriving this summer

The Iowa Gardener: How to fix common problems - and when to toss a plant and start over

Veronica Lorson Fowler

Setting a pot into a dish of water helps really dry soil better absorb the water.
Veronica Lorson Fowler Setting a pot into a dish of water helps really dry soil better absorb the water.
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Keep your pots, baskets, window boxes and planters looking lush and beautiful even when Iowa’s weather goes hot and dry. All it takes is consistent care and a little know-how.

  • Provide the right amount of light. Most Iowa gardeners provide too little light. Even impatiens need at least four hours of full sunlight a day to bloom and grow their best. Others, such as petunias, geraniums, and other sun lovers need at least six hours of full, direct sunlight a day. Any less and the plants won’t thrive and will appear sickly with few and small blooms.
  • Water generously. In hot weather, smaller containers can need watering as much as twice a day (a good reason, frankly, to go with large containers as much as possible). Even with larger containers, moisture-loving plants such as hibiscus need watering every day, including during cooler weather.
  • Mulch your containers. Use shredded bark or other mulch to lay a half-inch or so layer of mulch. It helps container moisture.
  • Make watering easier. Cluster your containers together. It saves time and it looks good.
  • Completely dry? If a pot dries out completely, often the soil will shrink away from the sides. Then when you water, all the water just rushes down the sides, out the pot, and isn’t absorbed by the roots. Remedy the situation by sitting the pot in a bowl, bucket, or big plastic box filled with water halfway up the sides of the pot. Let it sit for an hour or two. The water will slowly wick up through the bottom and completely rehydrate the soil.
  • Pinch your plants. Pinch off discolored leaves and faded blooms every time you water. This keeps plants attractive, prevents the spread of disease, and encourages further bloom.
  • Fertilize regularly. Constant watering flushes nutrients out of the container’s soil. Work a granular slow-release fertilizer, such as Osmocote, into the soil at planting time. With flowering plants, fertilize them with a bloom-booster type liquid fertilizer every two to three weeks, as directed on the label. It doesn’t cost any more than other fertilizers, and it really does push them to bloom far better. With foliage and other plants, use a general-purpose fertilizer, such as fish emulsion or regular Miracle-Gro, as directed on the label every two to three weeks.
  • Got bugs? Try this homemade version of commercial insecticidal soap formulations: Mix 1 to 2 tablespoons liquid soap (such as hand soap, not dish detergent) into 1 quart water. Put in a spray bottle and coat the leaves, stems, and undersides of the plant. Repeat in five to seven days and five to seven days after that. This works best on soft-bodied insects, such as aphids, thrips, white flies and spider mites — the main attackers of houseplants and container plants.
  • Cut your losses. Doing all these things and the plant looks like heck anyway? Pitch it. After all, we have container plantings to make our spaces look better, not worse. Container plantings aren’t meant to last forever. If the plant gets sick or spindly, toss it in the compost heap and resolve to do better next year.

June’s to-do list:

June is a busy month in the garden. Here is a list of what you need to do.

  • Divide perennials that bloom in spring now, as needed or desired. Hold off on dividing those that bloom in late summer or fall. For them, it’s too close to show time.
  • Deadhead flowers on annuals, perennials and some shrubs. It keeps your garden more attractive and in many cases, it will encourage more flowers longer.
  • Weed, weed, weed. Try to time your weeding for the day or two after a rain. It makes getting the roots and all much easier.
  • After weeding, mulch to prevent weeds from returning. I recommend 1 to 3 inches of wood chip (aged, never fresh) mulch around plantings.
  • Continue to plant container-grown or balled-and-burlapped trees, shrubs, and roses now. However, avoid planting bare-root roses and other bare-root plants. This late in the growing season, they’ll struggle to get established before winter.
  • Time to practice tough love. If a tree or shrub still is struggling with winter damage or overall sickness, with significant amounts of dead wood, it’s almost certainly time to dig it up or cut it down.
  • Remove the browning foliage of tulips and daffodils once it pulls away easily. Until then, the plant is using it to rejuvenate for next year.
  • Pinch mum buds until the Fourth of July. This helps them produce larger, bigger flowers on stronger stems.
  • Harvest early and often for the most tender, sweetest produce and to keep plants producing well. Pick zucchini, for example, with the yellow flower still attached
  • With the unusually hot weather, lettuce might be starting to bolt, that is, send up tall, elongated stalks. At this point, it turns bitter. Pull it up and pitch it on your compost heap.
  • Remove old raspberry canes after plants stop producing fruit.
  • It’s never too early to check out the bulb catalogs and online. Ordering now assures the type and quantity you want this fall, when supplies run low.

l Veronica Lorson Fowler is co-publisher of The Iowa Gardener website at theiowagardener.com.

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