17 Oct 2022 11:09

Planting tulip bulbs in the greenhouse

Fancy a cup of tea in the greenhouse with lots of blooming tulips?

Autumn is here. There is more rain, colder temperatures and the days are shorter. Nonetheless, there is a lot you can do in the greenhouse at this time, which you later can enjoy in spring – and which would save you money.

The tomato plants are long gone, and the winter cultivation has started in the greenhouse. However, I still have some space left. In October, I always plant tulips in the greenhouse. Especially with the energy crisis in the UK and in Europe in general, tulips bought in stores will become way too expensive to afford next spring. So why not plant your own? – It is much easier and cheaper.

Here at Spirekassen, we usually plant what is left of the tulip sales in the greenhouse.


Planting tulip bulbs

Tulip bulbs should be planted between October and November.

Most tulip bulbs need to be planted 10 cm deep. If you have garden beds in the greenhouse, plant the tulips in the beds. If that is not the case, you can use pots as well. But remember to make sure that the water can drain away.

In the greenhouse, I always plant the bulbs close to each other. A few centimetres between each bulb are enough. The reason for this is that each tulip will reach for the light when they are planted this close. By doing this, the tulips will be great for bouquets.

The trick is to plant every other bulb upside down with the pointy end facing down. This way the blooming will be delayed resulting in a longer blooming season.

Cover the newly planted bulbs with soil and sparsely irrigate them during winter. Now you only have to wait for spring. There is no need for additional heat, nor do you have to be worried about frost. The tulip bulb takes care of it all, except from moist soil with no drainage – in worst case the bulb will start to rot.


Make use of the greenhouse

If the tulip bulbs are planted in the greenhouse in autumn, you can expect a very early blooming in March. Spring tulips produced in the industry need a lot of energy to be produced. So, there is quite a lot of money to save by cultivating them yourself. Last year, Spirekassen was self-sufficient in tulips from March to May. When it was time to say goodbye to the tulips, the tomato plants were then moved to the greenhouse. This way, the greenhouse is also used the first couple of months of the year.

The cheapest varieties

If you are looking for an inexpensive way to start your tulip adventure in the greenhouse, then begin with the Darwin Hybrid mix or Triumph tulip mix. These varieties are often the cheapest option. It can sometimes be an advantage if you want a wide range of colours. If the tulips are intended to be used in bouquets inside, do not expect the bulb to flower the following year. Although both the Darwin Hybrid and the Triumph tulips are able to rebloom if they are not picked.


The tulip theory and fun facts

For us, the main function of a tulip bulb is to bloom. Tulips bloom naturally in spring but needs to go through a long process before it can start to bloom. Those bulbs that you can buy in autumn are in a hormonal dormancy, and the dormancy must end before the tulip bulb can bloom.

After you have planted the bulb in autumn, it is important that it goes through all the stages so it can bloom the following spring. The main goal of these stages is to break down the dormancy hormones in the bulb. First, the tulip bulb must be in a ‘cold period’ for about 15 to 20 weeks. The temperature should be around 9 degrees Celsius during some of this period. The bulb will start to take roots and grow leaf buds and flower buds. After the 15 to 20 weeks the tulip bulb is ready for forcing. At this stage the bulb needs heat and lots of light. With a greenhouse, you do not have to do anything the first couple of months. After 2-3 weeks the tulips will have grown green leaves and flower buds.

You cannot skip a stage and think you can start with planting the bulb in spring. The bulb will never reach the blooming stage, since it has not been ‘woken’ from its dormancy. The weeks with cold during winter have the purpose of breaking down the sleeping hormones in the bulb. Therefore, the tulip bulb must be planted in autumn, so the cold period can be completed naturally by the cold months.


Om Spirekassen

Christine Wiemann is a greenhouse grower and an agricultural technician and owner of the seed company Spirekassen. Christine is an author of several books about lifestyle, garden life and plant cultivation. Today she writes blogs and shares her knowledge and passion for greenhouses. Christine is a greenhouse expert and an ambassador for Juliana Drivhuse.

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