Gardening: How do we force last year’s poinsettia to rebloom?

Q: We kept our poinsettia from last Christmas, and it has done well over the summer. We want it to bloom again for Christmas, but we can’t find the clipping of the newspaper article you wrote about what to do. So, what do we do?

A: There are several basic environmental requirements that need to be matched, but the main one is long nights and short days. Most poinsettia varieties will bloom if you give them 14 hours of darkness each day. Figure out when you go to sleep and when you leave for work, and set up a schedule you can follow. If you can uncover the plant when you leave for work at 7 a.m., you will have to put the plant in the dark by 5 p.m. each day. The actual start and end times don’t matter as long as you can reliably keep it in the dark for at least 14 hours every day.

Covering the plant with a box may be easier than moving the plant to a dark closet or room each day. If there are some long stems sticking out, they can be pinched to make the plant bushier, and it will have more flowers.

Nighttime temperatures should be in the 60- to 70-degree range, with the daytime about 10 degrees warmer. During the day, it should be in bright light but not necessarily full sun. Water as needed, and fertilize following the label directions for a fertilizer that promotes flowering. It should start to bloom in eight to 10 weeks. Start the long night treatment in mid-September through the beginning of October, and the plant should be blooming for the Christmas season.

Q: We have noticed that the pretty, pink-leaved sweet potato vine we have growing in a hanging basket has been growing some big sweet potatoes. Can we save them for next year, or can they be eaten?

A: They can be saved, or they can be eaten. But they are usually rather small and don’t store well for very long. Plus, they are grown for their pretty leaves and not how they taste, so they may not be worth eating.

If you want to try, then you will do the same treatment we do for sweet potatoes from the garden. They store best if cured for about a week after being dug up. If they are not cured, they tend to decay quickly in storage. Place them in a warm, humid room in the upper 80-degree range, with damp towels, if necessary, for increasing the humidity. The curing helps toughen up the skin, and it helps convert starches to sugars, making the sweet potatoes sweet.

Q: I was given a few mint cuttings this summer. They are sending out plenty of roots. I like having the mint leaves in my tea every few days and want to keep doing it over the winter. They are growing in a hanging glass container, and I don’t have room for a flower pot near a window. How can I keep them growing in water? Or do I need to plant them in soil?

A: Mint cuttings do last a long time just growing in water. They eventually will need to be fed some nutrients. A regular house plant fertilizer won’t have all the micronutrients they need. You will want to use a fertilizer designed for feeding plants growing hydroponically.

Or you can plant the cuttings in potting soil in a hanging pot and use a complete house plant fertilizer.

Email questions to Jeff Rugg at

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