Real Solutions: Garden Tips Before Winter
Our canna lilies and dahlias bloomed fabulously this summer, but I understand they’re not hardy enough to survive our winter outdoors. What do you recommend? — D.C., Antrim, NH
Cannas, dahlias, elephant ears (Colocasia), gladiolus, caladium, and tuberous begonia, among other tropical plants, are becoming increasingly popular for home gardens, adding exotic effects. But these tropicals — and most other summer-flowering plants that have tender roots, rhizomes, bulbs, corms, or tubers — don’t tolerate New England winters outdoors. If properly prepared, dug, and stored indoors until next spring, the root parts of these plants will survive, and the plants will continue to thrive, giving enjoyment for many years. Some, such as dahlia and caladium, prefer warm, moist winter storage, while gladiolus and cannas do best in cool, dry conditions.
Once you know how to handle them properly, saving them from year to year is simple. Make sure you correctly identify what type of plant you’re growing. Then ask the experts at your local garden center for specific instructions to ensure best results, or find the right information at the library or online.
The lilacs, forsythia, baptisia, and plume poppy in our garden are growing wildly and have taken over more space than we’d prefer. Should we cut them back before winter? – M.S., Greenwich, CT
Most woody plants, such as lilac and forsythia, are best pruned right after they finish flowering in the spring. But overgrown plants such as the ones you describe can be pruned now, as long as you understand that you’ll sacrifice some flowers next spring. For sure, you should remove dead, unhealthy, and broken branches. Thinning by cutting out a third to half of the stems may also help prevent winter damage from snow and ice. You may also tie any other overly lanky stems together to protect them from damage until you can cut them back in the spring. Wait until after they bloom next spring to cut back the tops, where most flowers grow.
Herbaceous perennials such as your baptisia and plume poppy (Macleaya cordata) will benefit from a good pruning before winter. Once heavy frost discolors their foliage, cut them right back to the ground. The same treatment applies to most herbaceous perennials whose foliage becomes unattractive in fall. But wait until spring to cut back handsome plants such as the ornamental grasses; their gracefully waving foliage and flower heads can provide enjoyment all winter. Come next spring, consider transplanting your fast-growing types to areas where they have more space, or divide them.
We live in the city, and our “landscape” consists of various types of plants in pots and planters on our deck. Last year some plants (cotoneaster and hydrangea) didn’t survive the winter. Based on recommendations from our local garden center, we replanted with juniper, daylilies, arborvitae, and ‘PJM’ rhododendron. Should we be doing anything else to ensure their health next year? — N.J., Boston, MA
Your local garden center was correct in recommending plants with root systems that will survive Boston’s normal winter temperatures in above-ground pots. Although their tops are plenty hardy, the roots of the types you lost are susceptible to cold damage and need warmer in-ground protection in this region.
Even when you use plants that tolerate cold root conditions, it’s important to maintain proper soil moisture around those roots. Continue watering your pots and planters right up until they freeze; then check and adjust moisture during winter thaws so that they never dry out. Protecting your plants over the winter from drying winds and late-winter sun is also a good idea; try grouping your pots together close to the building.