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Forcing Paperwhite Narcissus

Most fall-planted bulbs require a period of cool temperatures before they form flower buds and bloom, but Paperwhite Narcissus, or “Paperwhites,” which come from warm, Mediterranean countries, will bloom without any special temperature treatment.  This makes them ideal for forcing into bloom indoors.  (If “forcing” sounds too violent, think of it as coaxing, or encouraging.) The most commonly available paperwhites are white, but there are also yellows.  They are closely related to the garden daffodils (same genus; Narcissus), so if you look closely, you’ll see that the inflorescences consist of clusters of small, fragrant daffodils.  Forcing paperwhites is really easy, but I’m going to go into some detail below to make it seem more mysterious.

From the time they are planted, they will be in full bloom from four to six weeks later depending on factors including the temperature of the room (warmer yields faster).  The bulbs are usually forced in a non-draining container without potting mix, using pea gravel, marbles, glass chips, stone chips or similar as the medium.  Place three or four inches of the gravel in the bowl, set the bulb on the gravel with the pointy side facing up, and the flat side (bulb plate, where the roots come from) on the gravel. The bulbs should be close but not touching, to reduce the chance of rotting. A good spacing would be five bulbs in a six-inch diameter container. Add water to the stones so that it is just below the bulb plate. The roots will sense the water and grow down into it.  If the bulbs themselves are in the water, the bulb will rot.  Add enough dry gravel to cover the bulbs about 2/3 deep, with the tops in the air; this will help keep them upright.

Initially the bulbs should be in a cool, dark spot (50 degrees is suggested by Leonard Perry at the University of Vermont Extension.  Click to read article).

He recommends moving them to a bright window at 60 to 65 degrees when the green shoots appear growing from the top of the bulb.  Check the water periodically to keep the roots in water but below the bulb plate; as the bulbs start to grow, the water intake will increase so you may wind up watering every two or three days at full bloom.  You don’t need to fertilize (feed) the bulbs; they don’t need it and it will encourage the growth of algae.

The big problem with paperwhites is that they tend to sprawl and may need to be staked.  But, William Miller at the Flower Bulb Research Program at Cornell University reported a neat trick to keep the flower stems shorter and stronger while maintaining the full size of the flowers, eliminating the need for staking (click to read article).

They found that adding alcohol (in moderation) to the water will reduce height by 1/3 from the normal 12 to 18 inches height.  They recommend pouring off the water (or I suggest extracting it with a turkey baster) when the green shoots are one to two inches high, replacing the water with an approximately 5% solution of alcohol in water, and to continue to water with this solution going forward.

This solution can be made from rubbing alcohol (isopropyl alcohol), 70% to start with; dilute 1 part alcohol to 13 parts water); or ethyl alcohol—gin, vodka, whiskey, etc. but not beer or wine because the Cornell researchers say that these contain too much sugar and will damage the plants.

Imbibers in the US generally buy alcohol that is labeled at a certain “proof;” e.g., 80 proof vodka.  The proof number is double the percentage alcohol, so 80 proof is 40% alcohol.  To make a 5% solution add 1 part 80 proof vodka to 7 parts water. (See calculations, below).  They caution against overdoing it; at greater than a 10% solution “growth problems will start, and 25% alcohol is dramatically toxic.”

Keep your bulbs in a cool, bright place as long as they are blooming, and enjoy their strong fragrance.  When they go out of bloom, discard them. You cannot get them to bloom again, and they will not survive outdoors in our Maryland climate.  Think of them as a long-lasting floral arrangement.  For longer blooming, plant bulbs several times over the fall or winter, a month apart.

Footnote: Calculating a dilution: start by determining the percent alcohol.  If you are working with “proof,” divide it in half.  So, let’s say you have some 30 year old Scotch and you were just going to throw it away anyway, and it’s labeled either 90 proof, or 45% Alcohol by Volume, and you are going to use this to water your paperwhites.  Solve for X.

X = % Alcohol/.05     X = .45/.05 = 9.   To get a 5% solution, take 1 part of your Scotch and add 8 parts of water.

 

by Larry Hurley, Behnke horticulturist

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