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At Plantasia, last weekend’s flower and landscape show, landscape pros, master gardeners and plant vendors saw more than 12,000 people and fielded many of the same garden questions and comments.

Here are some hot topics:

The impatiens situation

This was talked about extensively and bears repeating, so that we can save a lot of your dollars and disappointment: Impatiens, the flowering annual that everybody counts on for flowers in the shade, is afflicted with a disease called Downey Mildew. It has spread throughout Europe and America to the extent that many growers on both continents won’t be growing them at all. It’s not the fault of growers or retail centers, and there is nothing a gardener can do about it. The spores are invisible so you could take home a lovely six pack or 4-inch pot in June, but it is likely to collapse within weeks. The spores remain in the soil for several years, and the disease is also wind-borne.

Bottom line: Choose other plants for your shade gardens as recommended by your garden centers and experts; it’s a great year for begonias! Note that New Guinea impatiens including Fanfare, Divine, Celebration and Sunpatiens have high resistance to this disease. Other plant species are not affected. Tell your garden clubs and neighbors.

Caring for the plants you bought

The lust for flowers and green foliage, and a few good deals, drove sales of annuals, perennials, forced bulbs and some woody plants at garden shows this month, long before you would normally buy them in a garden center or nursery. The popular question then became: “How should you keep them until you can plant them outside – and when would that be?”

Perennials, such as the popular Helleborus and primroses, already flowering, need a gradual transition from life in a greenhouse or flower show to life outside. These perennials (and most you saw) are cold-hardy, and hellebores actually flower in winter months, but they have been in a warm place.

Your job: Water and drain them when you get home and enjoy the flowers, but keep them as cool as possible (preferably in the 50s or low 60s), in good light. When you can dig outside, gradually “harden them off” and plant them. A frost won’t kill them and they should grow all season and flower next spring.

Woody plants (unless they are houseplants) need the least time inside possible, as indoor rooms just dry them out, and they are supposed to be dormant in the winter. If the root ball has dried out, soak it well and get it outside. Stash these plants in a sheltered location. They will probably drop all their leaves, but later the increasing light and warm temperatures should induce new growth. Plant them when the soil permits, with some compost and slow-release fertilizer.

Potted bulbs that have been forced to flower ahead of schedule are a joy to behold, but you’d best appreciate them now because they will soon be finished for the season. After the flowers drop their petals, cut off the flower stalk and continue to tend the green-leaved plant until it’s no longer green. Water and fertilize lightly during this time. When the soil is warm outside, plant them in the ground (with a little bone meal or bulb fertilizer and compost) and mark them since it’s easy to forget where they are. They will probably grow and produce spring flowers in the normal time frame next season.

Sad state of houseplants

Many people wonder why houseplants start to drop leaves, get sticky, or tiny insect pests appear on them this month. Basically, they’ve had enough winter in our warm, dry houses, and they are ready (as we are) for more light and to get outdoors. When plants are stressed, pests and diseases emerge. Tend the problems with least-toxic methods, do some cutting back, and be patient. Most plants will survive until the good times.

More questions

Everyone is so eager for spring and gardening, so “When can I …” is the most constant type of question. Here are some of them:

Q: When can I put in the vegetables?

A: Cool weather vegetables can go in when the soil is workable, and it’s a tradition to plant peas at Easter time even in cold soil. Warm weather crops such as tomatoes need warm soil and warm nights, so wait until the end of May. (Read the seed packets.)

Q: When can I prune my roses?

A: Rosarians with sheltered locations sometimes prune roses lightly in fall and drastically in spring, but in cold regions it’s smart to wait until the risk of severe freezing has passed. That’s because rose stems often die back after a freeze from wherever they were cut. An old adage says: “Prune roses when forsythias bloom.”

Q: When can I prune the (hydrangeas, lilacs, Japanese maple, wisteria vine, clematis …?)

A: Each has its best time and routine. If a plant flowers in spring or early summer, prune it only after the bloom period. Most trees, including fruit trees, should be pruned now, while dormant, if needed. With most woody plants, when in doubt, do nothing. Most plants in the right place need no pruning, or very selective cuts. Never just flat-top or trim your shrubs routinely, and never top a tree. Pruning is something you can learn, but get a book, attend a class, or ask a pro before you go at it.

And finally: Certified Nursery & Landscape Professional Chris Premielewski, of C. Premium Landscapes, said he heard many favorable comparisons between the landscape displays at Plantasia and Canada Blooms or the Philadelphia Flower Show; many said our vendors were more diverse than in the Canada show. Even allowing for regional pride and bias, it sounds as if the Western New York State Nursery & Landscape Association’s show is placing well in the competition.

Both Premielewski and Roger Restorff, association director and CNLP, also observed that people said they liked seeing new ideas within a realistic landscape display – the feeling that “I could have that in my yard.”

My answer is: Yes, you can, but just not yet.

Sally Cunningham is a garden writer, lecturer and consultant.