Why won’t flower buds open on daylilies

One of the delights of daylilies is the abundance of flowers that they produce in summer, but what’s the reason why some of the buds don’t open? The problem is more pronounced in certain areas, but it seems to be spreading. At first glance it may not be obvious that there’s anything wrong – just one or two buds that don’t open on an otherwise healthy looking plant. But given time, you may find that the problem is much more noticeable and none of the flower buds open properly. The root cause could simply be that you’re not giving the plants the conditions they need, but a tiny menace in the form of hemerocallis gall midge is starting to vex gardeners by damaging the buds before they get chance to open.

And, as the blooms of these popular plants only last a day, as their name implies, it’s crucial that you make every bud count. With careful observation and a little know-how, you can maximise the performance of your plants and ensure the best show for summer.

What stops daylily flower buds from opening

Hemerocallis gall midge made its first appearance in the UK in 1989 and since then has been spreading to affect plants throughout England, Wales and parts of Scotland. It is also established in others parts of the world where daylilies are grown. The main symptoms of infection with this pest are that the flower buds are abnormally swollen, with some puckering of the immature petals. Infected blooms are often discoloured and fail to open.

The damage is caused by the larvae of a tiny fly that lays its eggs at the top of the developing flower stalk, just as the buds are starting to swell. Once the eggs hatch, the resulting larvae start to feed on the sugary tissues of the bud. This causes the cells of the developing flower bud to divide in a less organised way, distorting it and stopping its development.

Breaking open the damaged buds reveals the larvae themselves, in the form of see-through, fly maggots, 2-3mm in length. Early- and mid-season varieties of hemerocallis are most affected due to the lifecycle of the fly. Daylilies that flower from late July onwards are usually unaffected. And while it damages the flowers the rest of the plant remains healthy and unaffected.

How do you get rid of hemerocallis gall midge

This fly and it’s larvae only infect hemerocallis plants. Once fed, the larvae drop from the plants and turn into cocoons which survive in the soil to hatch into the adults in the following spring.

There is no chemical treatment available for the prevention of hemerocallis gall midge and the only way to limit its incidence is to check the plants assiduously and pick off the infected flower buds. These should be destroyed, along with the maggots. Infected plants nearby in other gardens may provide sources of re-infection. Physical barriers in the form of fine horticultural mesh may prevent the adult flies laying their eggs on the developing flower buds, but it is difficult to surround the tip of the entire flower stalk. Birds and amphibians may take some of the adult flies and larvae, but do not appear to offer high levels of control.

So, sadly, until an effective biological control is introduced, there seems to be little that can be done, other than hand picking or avoiding early varieties of these lovely flowers.