Autumn Planting Tasks for Bulbs in Containers

Why Autumn Is the Best Time to Plant Bulbs in Containers

Spring can feel a long way off when the evenings are drawing in, but autumn is exactly when next year's display is won or lost. Bulbs planted now have weeks of cool, moist weather to put down roots before the cold really bites, and that root growth is what carries them through winter and into flower.

In a pot, timing matters even more than it does in the ground. Bulbs in a border can send roots down to find moisture; bulbs in a container are entirely dependent on the compost you give them. Plant too late and the compost is cold, growth is slow, and flowering can be thin and short-lived. As a rough guide, plant daffodils, crocus, muscari and alliums from early September, hyacinths and snowdrops in late September and October, and tulips in November. Tulips planted in cold soil are far less troubled by fungal problems, so there is no need to rush them.

Getting the Compost and Drainage Right

Soggy compost is the single biggest killer of bulbs in pots, so drainage comes first. A gritty, free-draining mix is what you want: a peat-free multipurpose compost blended with about a quarter by volume of horticultural grit works beautifully, and John Innes no.2 with the same grit added is even better for larger pots because it holds its structure for longer.

• Choose containers at least 30cm deep if you plan to layer bulbs, and always check there are drainage holes.
• Add a layer of broken crocks or gravel over the drainage holes to stop them silting up.
• Stand pots on pot feet or small blocks so water can escape freely and the base is not sitting in a puddle.
• Terracotta looks lovely but can crack in a hard frost; glazed ceramic or frost-proof plastic is safer if your pots stay outdoors.
• Never reuse old compost from a diseased or waterlogged pot — start fresh each autumn.

How to Layer Bulbs for Months of Colour

The technique often called lasagne planting lets you fit dozens of bulbs into a single pot and stagger the flowering over several months. The principle is simple: the biggest bulbs, which need the most depth and flower latest, go at the bottom; progressively smaller bulbs go above; and low-growing spring bedding sits on the surface.

As a rule of thumb, bulbs should sit at roughly two to three times their own height in compost, with at least 5cm of compost below them and a good 10cm of compost above the top layer. Space bulbs so they are almost touching — close planting in a pot looks generous rather than crowded, and the bulbs push each other upwards rather than rotting.

A Simple Layering Plan to Copy

Fill your pot with compost to the depth of the first layer, then work upwards, adding compost between each tier and firming gently as you go.

• Bottom layer: tulips, planted about 20cm deep, roughly ten to a 30cm pot.
• Second layer: daffodils or narcissi, around 15cm deep, spaced so they are just clear of each other.
• Third layer: hyacinths or muscari, about 10cm deep, again close but not touching.
• Top layer: crocus, iris reticulata or snowdrops, around 8cm deep.
• Surface: winter pansies, wallflowers or a small heather to give the pot interest through the darkest months.

If you would rather keep things simple, two layers — tulips below and crocus above — will still give you a display that lasts six weeks or more.

Planting, Watering and Protecting Your Pots

Water the pot thoroughly after planting so the compost settles around the bulbs, then keep it only lightly moist through winter. Compost that stays wet for weeks on end is far more dangerous than compost that dries out a little, so resist the urge to water every time you pass with a can. In a mild, dry winter, a drink once a fortnight is plenty.

Squirrels, mice and even foxes will happily dig up freshly planted bulbs, so cover pots with a sheet of chicken wire or a layer of sharp grit until the shoots appear. As the hardest frosts arrive, wrap terracotta and thin-walled pots in bubble wrap or hessian, or simply move them against a sheltered wall. The bulbs themselves are perfectly hardy; it is the compost freezing solid and the pot cracking that causes trouble.

After the Flowers Fade

Move pots into a bright spot as soon as shoots appear in late winter and water more freely as growth accelerates. Deadhead spent flowers so energy goes into the bulb rather than seed, but leave the foliage in place for at least six weeks — it is feeding next year's bulb. A liquid tomato feed every fortnight from flowering until the leaves yellow will pay dividends.

Tulips rarely perform as well in a second year in a container, so treat them as annuals and start again each autumn. Daffodils, crocus, muscari and snowdrops, on the other hand, will happily return, provided you let the foliage die back naturally in a sunny spot and keep the compost from drying out completely in summer. Once the display is over, the same pot can be replanted with summer bedding or herbs, ready to be layered up all over again when autumn returns.