What to do with bulbs that don't have flowers.

Nathan Lange plantsman@comcast.net
Fri, 15 Apr 2016 15:58:51 PDT

In North America, decreasing year to year tulip flowering is a very 
common problem across the Midwest and points further east, locations 
that always receive more than enough cooling. The descriptions are 
nearly always the same with 100% flowering the first year after 
planting with a rapid decline in flowering thereafter. In general, 
one of the responses of flowering size tulips bulbs to adequate 
venalization is to divide into smaller bulbs. In the Midwest, spring 
is very short and quickly followed by hot summers. Late spring high 
temperatures induce tulip leaves to senesce too soon, long before the 
young daughter bulbs have grown large enough for flower induction. 
Instead of flowering plants, multiple leaves are produced the 
following spring from a clump of small bulbs where each original bulb 
was planted. For many tulip cultivars, repeat flowering is virtually 
impossible because the bulbs constantly divide year after year, never 
achieving an adequate size for flowering. In the Midwest, this 
problem can primarily be avoided with proper tulip selection and, to 
a lesser degree, with adequate fertilization.

Houston is not in the Midwest and concerns about inadequate cooling 
are legitimately cause for concern. However, remember that 100% of 
Sujit's bulbs flowered the first year and 70% flowered the second 
year. In those years, at least, the bulbs did receive enough cooling 
to flower. We don't really know what happened the first year since 
the bulbs may have been partially precooled before they were 
purchased, but the bulbs did receive enough cooling the second year 
to result in 70% flowering. Furthermore, the flowering stalks were 
the height that was expected of them. This is key information since 
the height of the flower stalk at the time of flowering for many bulb 
plants, especially tulips, is primarily influenced by the amount of 
prior vernalization. Cooling does not cause flower induction in 
tulips. Warm temperatures during the previous summer induce flowering 
which is not ever going to be a problem in Houston. Cooling is 
required for elongation of the flowering stalk. Too little cooling 
can result in very short flowering stalks with flowers down very low 
among the leaves. Even less cooling results in aborted flower buds. 
(Too much cooling causes very tall floppy tulips.) Between the 70% 
flowering reported for the second year and the normal heights of the 
flowers, Sujit's plants seem to be getting enough cooling. Also, it's 
possible that only 70% of the original bulbs survived and 100% of 
those remaining flowered the second year.

Now that we know that this tulip population has thinned since 
planting, it's safe to say that other cultural requirements are not 
being met. A thinning tulip population implies that the average bulb 
size is decreasing. Bulb size is everything if you want flowers. This 
point cannot be stressed enough. Especially in areas with marginal 
cooling, larger bulbs are especially important for successful 
flowering. Fertilizing is always extremely helpful in producing large 
tulip bulbs. There are plenty of online recommendations for properly 
fertilizing tulips.

In summary, inadequate cooling does not seem to be the problem here. 
One or more other cultural requirements (e.g. fertilization, 
irrigation, lack of pests) is not being met resulting in a declining 
population with bulbs that are no longer large enough to flower.

Nathan



At 04:36 AM 4/15/2016, you wrote:
>All,
>
>Thank you for all the responses and advice.  The flowers from the first
>year were at the height I expected and so were the second year but much
>fewer.  Now the population have thinned with only healthy leaves.  I will
>experiment with some of the suggestions. Lifting some in the fall and chill
>and replant in the spring and also fertilizing the rest in the fall. I will
>report the results next spring.
>
>I will put one of the Buphone in the ground.
>
>Warren, I will try to call you this evening.
>
>Sujit






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