Compared to many other plants, flower bulbs are low-maintenance.
Few specific tasks are required other than weeding and fertilisation of perennial plantings. Be careful when hoeing borders and beds, as this may cause considerable damage underground. If a lot of hoeing is required, it may be wise to plant the bulbs a little deeper than is indicated.
The great thing about flowering bulbs is that they are relatively low-maintenance. Annual bulbs require no attention at all. Perennial plantings will require some fertiliser, but that is about it, which makes them ideal as garden plants. Annual bulbs require no additional feeding, they have everything they need stored inside the bulb. Perennial bulbs extract a lot of nutrients from the soil, so they do need supplementary feeding. Artificial fertiliser is the best choice during the growing season: it contains the ideal mix and concentration of nutrients. It also dissolves readily, making it easier for plants to absorb. Artificial fertilisers should not be used outside the growing season, as the nutrients will be flushed away and lost. Go easy on artificial fertilisers, as excessively rapid growth leads to weak plants which easily succumb to disease and infestation. Overfertilisation can also lead to burning of leaves.
Appropriate fertilisation can prevent disease in plants and makes them less vulnerable to disease and pests, reducing the need for pesticides. Proper fertilisation also enhances the soil structure.
There are various fertilisers to choose from:
- Compost and animal manure. These are organic fertilisers. As mentioned above, they also improve the soil.
- Natural fertilisers used to supplement organic fertilisers.
- Artificial fertilisers.
The type of fertiliser to choose depends on the type of planting and the application time.
Flowering bulbs have all the nutrients they require for their first season of growth already stored inside the bulb. Additional fertilisation is not required for flowering bulbs as part of an annual planting scheme.
With perennial plantings it is important that plants and flowering bulbs receive supplementary fertilisation, to make up for what they extract from the soil.
In existing borders, a common solution is to use artificial fertilisers.
Artificial fertilisers contain concentrated plant nutrients like nitrogen, potassium, phosphorus, magnesium and calcium. Artificial fertiliser contains nutrients in precisely the required proportions and concentrations, whereas these may vary widely in animal manure and compost. The lack of organic materials makes artificial fertiliser unsuitable for providing a good soil structure.
Artificial fertiliser usually dissolves easily and can then be taken up by the plants. It should therefore be used during the growing season. When applied outside the growing season it will be flushed away before the plants can benefit from it. This will also lead to ground and surface water contamination.
The composition of fertilisers is generally indicated on the packaging by numbers, in a format such as 10 + 5 + 3. This means: 10% nitrogen, 5% phosphate and 3% potassium. A fourth figure will refer to the percentage of magnesium. Overfertilisation can cause excessively rapid growth, resulting in weak plants which are vulnerable to pests and disease. Plants may be "burned" by granulated artificial fertilisers which deliver nutrients directly, causing leaves to turn yellow and wither.
If the soil structure requires improvement, the use of organic fertilisers is therefore highly recommended, supplemented if necessary with specific artificial fertilisers to compensate for any missing nutrients.
Self-propagating plants and flowering bulbs are in their natural location. Nature is in balance here, as soil type, structure, water economy and planting all work together. The use of fertiliser in such a balanced situation is not recommended.
However, a number of symptoms (often visible in plant leaves) may indicate a shortage of certain nutrients. In such situations, the use of supplementary fertilisers is recommended. Organic fertilisers should be used, as these are more suitable for a natural environment.
Supplementary fertilisers containing phosphorus or potash (Condensed Molasses Solubles, a waste product from the food industry) can compensate for specific shortfalls in plant nutrients. Finally, lime-based fertilisers, such as marl (chalk from coral/algae), can be used to adjust soil acidity.
If this is applied only once each year it is important for bulbs that this should be done immediately after flowering.
To guarantee profuse flowering year after year it is necessary to enrich the soil once a year with fertilisers. Spring fertilisation is not recommended as it is better if the grass grows more slowly while the foliage of the flowering bulbs is still dying back. Autumn application is therefore to be preferred, as this will benefit both the grass and the bulbs.
For artificial fertilisers it is normal to apply 2 kilograms (12-10-18 per 100 m²) in three doses. It is also possible to use organic fertilisers, for example blood, bone and horn, compost or dried and pelleted cow manure. The ideal time to spread fertiliser is during or just after rainfall: the constituents of the fertiliser will then dissolve more readily.
In pots and containers
One important property of potting compost is its capacity to retain water over an extended period of time, as this will prevent flower bulbs from drying out during growth and flowering. With a single annual flowering, fresh potting compost will suffice.
If bulbs are used in hanging baskets it is important to enrich the potting compost with fertiliser. Often this is supplemented with feed tablets. These contain all the necessary nutrients for houseplants as well as terrace, balcony and garden plants. The tablets are easily administered by poking a hole in the soil and dropping the tablet into it. This will provide nutrition for at least 4 weeks. Since the tablet dissolves slowly, the nutrients are delivered gradually to the root system, which prevents root burning. Another option is to replace the potting compost used for pots and tubs annually with fresh potting compost.