Answer: First of all, it's probably not your fault. These are notoriously difficult to keep from year to year, primarily because they need a very long growing season. Growing them in pots adds an additional stress although it may allow you to start them earlier and keep them going longer in the fall. Alternatively raised beds of sandy loam in a warm microclimate might also help. A rich, moist yet well drained planting mix is good. Regular fertilizing with a balanced water soluble fertilizer including micronutrients plus an occasional dose of compost tea and kelp might also help. When you plant them, put them about two inches down and water well, then don't water again until they emerge. After that, water moderately. A water holding polymer in the soil mix might help if they are in pots. In any case, they will only bloom in the fall no matter what you do. Most people simply buy top quality new blooming size tuberoses every spring -- but here's how to dig and store them in the fall.
To be quite honest, tuberoses (Polianthes tuberosa) can
be "touchy" to keep over from year to year, and often do
not bloom well if at all after the first year, so don't be too
disappointed if it doesn't work.
Remove all but about 3 inches of the foliage now, then
remove the rest when it is quite dry. Do not remove the
offsets until planting time. (They will need a year or two to
reach blooming size, so it is up to you whether to keep them
Some gardeners allow these to dry with a nice lump of soil
attached, others prefer to wash them. Washing does
provide an opportunity to inspect them for imperfections
and any damage which might cause rot during storage. In
either case, let them dry thoroughly before storage and keep
them dry until they are replanted.
If washed, store them in a cardboard box or paper bag in
layers covered with sand or peat moss so that they don't
touch. Keep the package in a dark place with good air
circulation at about 60 degrees. If they are still encased in
dry soil, add enough filler as needed to ensure they don't
touch and store a bit cooler.
I hope this helps!
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