When to Plant Autumn Flowering Bulbs

Spring flower bulbs are a promise of excitement in the winter, but planting flower bulbs requires the right timing and conditions. They can’t be planted whenever the mood strikes. If they are planted at the wrong time, the end result can be frustrating. If planted too early, they can rot. If planted too late, the conditions can make it difficult for them to develop a strong root system. The window is small, and it is important to know.

For autumn-flowering bulbs, it is summer when they need to be planted. If done in late summer, the blooms will surprise you with their early arrival in the fall.

Planting Autumn Flowering Bulbs

Autumn flowering bulbs also behave differently. Bulbs such as Colchicum, also known as autumn crocus, go in from late July to early August, as they are very eager. If left on the shelf for too long, they will start to bloom, and become a problem rather than a charm. So, make sure to plant them as soon as they are purchased.

Sternbergia lutea – goblet-shaped and yellow perennial that many skip growing – should be planted in late July or August. It prefers a warmer climate and needs a spot that is less clayey and free draining.

Also, as dramatically autumn flowering are the Nerines. This flowering bulb is a bright pink flowering bulb (Nerine Bowdenii) and can set tufts in your garden as late as October and November when a lot of your garden is dying off. They do require a lot of growing time so should be set in the spring. They should be set against the base of a south wall to allow the bulb to protect itself.

Soil should never be neglected in bulb planting, especially with these. Ideally under bulb roots, the soil should never be waterlogged as most bulbs will spoil. After the spring rains you might want to consider a raised bed if the soil is consistently wet. It is disappointing to show poor effort early on.

It is a perennial concern to have an autumn flowering bulbs garden remain fertile every year, which goes to show how low the fertility of bulbs is. A little layer of low-nitrogen fertilizer in the early spring is ideal. Once the foliage dies back, it is always a sufficient maintenance to energise the bulbs.

Depth and spacing

As a rule of thumb, planting bulbs at a depth of two to three times their height is ideal. Bulbs of a smaller size such as crocus can be placed 8–10 cm in the soil, while the larger colchicum can be placed 10–15 cm in depth. The depth and spacing depend on the number of bulbs you plan on planting. For a more natural and gardened look, you should plant bulbs closer to each other. And for a more structured garden, plant the bulbs with more spacing.

A note on naturalising

Naturalising bulbs like autumn crocus and colchicum in the grass also helps with the natural look of your garden. Until the leaves die back in spring, hold off the mowing (this usually happens in May or June). For weeks it does look unkempt but if you mow it before the leaves die back, it robs the bulbs, their energy for the blooms in the next year.

Getting the most from each season

If you have a fond appreciation for your autumn display, then you are in for a treat. Initially, the bulbs look nice and well spaced every few years but if they look too congested, just lift from the soil and remove the bulbs. This also helps with bulb distribution. The most important thing with autumn flowering bulbs is knowing when to plant; now you are more knowledgeable.