Garden columnist Dan Gill answers readers’ questions each week. To send a question, email Gill at firstname.lastname@example.org.
I am concerned about getting my Christmas cactus to bloom. I’ve heard all kinds of recommendations and treatments to make them bloom. — Janice Landry
Christmas cactuses are triggered to bloom by nights over 12 hours long and/or chilly nighttime temperatures below 65 degrees. This is easily achieved by leaving your plant outside if that is where you have it.
Or, place your plant outside right now (this should normally be done in late September). Plants outside will receive naturally long nights and chilly night temperatures in October and early November. Do not place the plant in a location where porch lights, flood lights or street lights shine on it.
Bring the plant inside on those nights when temperatures will fall below 40 degrees. When you start to see the little buds forming at the tips of the branches, be sure to water often enough to keep the soil evenly moist. If it gets too dry, it may drop buds.
Move the plant indoors when the buds are about an eighth of an inch long and place it in a window for display. If the branches are pendulous and hang down, boost up the pot so the branches hang gracefully.
I would appreciate knowing how to separate ginger lilies and when. They are very freefying plants and seem to multiply easily given enough water. —Maggie DeGrasse
Separate your gingers in late March or early April. Cut back any growth that is dead or damaged from the winter, dig up a clump, divide it into as many pieces as you like (not too small) and replant them. Cut through the thick rhizome with a large knife. Easy as pie.
You can actually divide gingers anytime from late March through August. When dividing gingers during the summer, make sure you keep the newly divided plants well watered.
I have some running roses (not any of the new hybrid variety) that have been growing on my fence line for the last 15 years. I wanted to know if I should prune them back before next spring. —Robert Blanco.
It would probably not be a good idea to do extensive pruning on your running rose. These roses are almost always once-blooming — that is, they bloom heavily in late spring and early summer and then don’t bloom at all the rest of the year.
They produce those flowers on the growth they made the summer before. So, the growth your running rose made this summer will produce your flowers next year. The more you prune from now until they bloom next year, the more you will reduce flowering.
The best time to do extensive pruning to these types of roses is in midsummer, after they finish flowering (and how you would do that depends entirely on how you are training the roses).
On the other hand, if yours is an everblooming running or climbing rose, it would have bloomed on and off all summer and likely be budded and/or blooming now. The best time to do major pruning in that case would be late January/early February and another less severe pruning in late August/early September.
There is white stuff on the fronds of my sago palm. It’s not on the whole plant yet. I would appreciate your input on saving this sago. — Arthur
This is cycad scale, an insect pest that is showing up on many sagos (Cycas revoluta) around the area now.
First, prune off the worst looking, now heavily infested fronds. Then spray the sagos thoroughly covering all surfaces (get under the leaves) with a horticultural oil, such as Volck Oil Spray, Year Round Spray Oil or All Seasons Spray Oil. Make three treatments spaced 10 days apart.
The scale may persist for a while on the fronds, but after three treatments they are dead.
FERTILIZE BULBS: A variety of bulbs are beginning to grow now and will be in active growth over the winter, including Louisiana iris (Iris), calla lily (Zantedeschia aethiopica), Easter lily (Lilium longiflorum) and spider lily (Lycoris). Reliably perennial spring-flowering bulbs planted in past years will be producing foliage over the winter (such as narcissus, Dutch iris, star flower and snowflake). All of these plants could be fertilized now with a general purpose fertilizer following label directions.
SPECIAL ARRANGEMENTS: Many ornamental grasses are producing attractive flowers or seed heads this time of the year. The rosy-pink clouds of muhly grass (Muhlenbergia capillaris) flowers look amazing now. Grass plumes look fantastic in arrangements indoors alone or combined with other dried materials. Spray the flower/seed heads with a light application of hair spray or clear shellac to keep them from shattering as they dry.
DON’T STRESS ABOUT CRAPE MYRTLES: If your crape myrtle trees are looking bad right now you are not alone. Rainy weather in mid- to late summer encouraged outbreaks of Cercospora leaf spot, which caused a lot of defoliation. As a result, many crape myrtles have thin, unhealthy looking canopies now. Not to worry, the trees will be fine. Fertilize in March to encourage lots of vigorous new growth.
TIME TO REPEAT: After a summer of enthusiastic growth outside, some container plants may be pot bound. Check and repot into larger pots if necessary.