Q: I had some really pitiful impatiens last year. They pretty much just sat there and didn’t do much of anything. A grower who grows his own annuals said that sometimes the big distributors will spray their plants with a growth retardant to keep the flowers from getting too leggy, and sometimes they overdo it.
When I planted, I put a little SoilMoist in the holes, watered with Plant Starter and put tanbark on the bed to keep in moisture. I fertilized regularly with Miracle Gro. I am really disgusted and wondering if I ought to just try something else this year.
A: I wouldn't give up yet. Impatiens can be some of the showiest annuals, plus you don’t have a whole lot of other options in shadier spots (begonias, coleus and browallia are alternatives).
A few things could be behind this. An overdose of growth regulator is a possible early-season explanation, but the effects of that would’ve worn off within a few weeks. We had a lot of rainy, cloudy weather last growing season, so that might explain a less-lush-than-usual performance.
But if your plants really fizzled, I’d be thinking a few other things.
First on the list would be clayish and/or poorly drained soil. Especially when topped with mulch, which can be counter-productive in wet spots, your soil quality could be the main culprit here (compounded by the rainy season).
Too much mulch is another problem I often see. Most annuals don’t like more than an inch of mulch, and they “breathe” better in lighter mulches such as chopped leaves or bark. When surrounded by 3 or 4 inches of shredded hardwood mulch (which people commonly call “tanbark”), impatiens really struggle. This mulch also tends to pack down and further impede the oxygen supply to the poor impatiens roots.
A third possibility is a weak variety. All impatiens are not created equal. Some are much better performers than others. Some of the weakest are the mass-produced, seed-grown varieties commonly sold at the box stores. Most of the time you wouldn’t even see a variety name on the labels. They’re sold as generic impatiens.
Next year, try a named variety from a garden center. ‘Tempo,’ 'Fanfare,' ‘Dazzler,’ ‘Minipatiens’ and ‘Accent’ are good examples.
Finally, impatiens sometimes run into trouble with a soil-borne fungus. In milder cases, you’ll see stunting and occasional plant deaths. In worse cases, the whole planting dies off. Again, some varieties are more disease-resistant than others, but you’re better off switching off to coleus, begonias or browallia for a few years until the fungus (often Pythium) dies off.