Tips on impatiens, amaryllis and butterfly bushes

DEAR JESSICA: I tried planting regular impatiens in ordinary garden soil and it seems to have worked. I only planted six plants, so I will see what happens next year with the disease. — John Neknez,

via email

DEAR JOHN: Basically, you got lucky. The pathogen Plasmopara obducens, which causes the downy mildew disease that has plagued impatiens these past few years, is not only soilborne — it’s airborne. I strongly advise against planting impatiens walleriana for the time being because if you should unknowingly bring home an affected plant, the pathogen will spread from your garden and exacerbate the problem in the area. Best if everyone avoids them until all is clear. Then, with a reduced risk of cross infection, future plantings will stand a better chance of success. This could take some time, however, so hang in there.

There’s a hybrid species of impatiens called Bounce, which isn’t susceptible to the disease and has grown very nicely in my own garden these past two summers. The plants have the same habit and flower count as your beloved wallerianas, and they even bounce back from severe wilt after a simple watering, hence the name. You might look for them next year instead.

DEAR JESSICA: I was fortunate enough to visit Keukenhof [Dutch flower garden] this past spring while on vacation in the Netherlands. While there, I ordered some tulip and amaryllis bulbs, which I recently received in the mail. I planted the tulips in October. I was about to plant the amaryllis as per the planting instructions that zones 1-10 were acceptable; however, all my gardening friends insist an amaryllis won’t survive Long Island winters.

— Bob Engeman,

Hicksville

DEAR BOB: Technically, amaryllis bulbs are hardy to zone 8 — 7b with protection. You live right on the edge, in zone 7, so this could be a gamble.

Many gardeners who plant amaryllis outdoors on Long Island dig them up in fall and store them indoors (in a dry, dark spot) for replanting the after spring, as they would dahlias. They could, however, survive outdoors if protected with a heavy layer of winter mulch. They might even return with no protection at all, but the severity of the winter will certainly play a role in their fate. So you have to decide how much risk you’re willing to accept, and factor in whether you’ll be able to order replacements, should you need them.

Either way, the bulbs should be planted outdoors in May, and not too deeply. Set them so the top of the bulb is right under the soil line. Keep the soil moist, and fertilize. Plants should be in bloom by midsummer.

DEAR JESSICA: I just planted three new butterfly bushes. I had butterfly bushes many years ago and have always cut them down to the ground in February. Should I do that with these new ones in February 2017 or give them a full year before cutting them?

— Marianne Fornieri,

via email

DEAR MARIANNE: I wouldn’t cut your plants down the first year. Let them use their energy next spring to establish a strong root system, not recover from surgery and push out new growth from cut ends.

In fact, if you’re happy with their shape and habit, you can probably leave them be the first three years.

Healthy, established butterfly bushes (Buddleia) should be cut down to 12 inches or less in February or March, as you have done in the past, before breaking dormancy every spring. That sort of hard pruning encourages more branching, a fuller habit and larger blooms.