One of the most common questions we are asked is: Can we grow spring flowering bulbs in pots? Well, the answer is a resounding yes, and here is how.
The general tenet here is the bigger the bulb, the bigger the pot! This is logical when you think about it; if you use little bulbs like crocus in a large pot their impact will be lost. Using big bulbs such as tulips in small pots not only looks out of whack, the plants or pots may topple over.
Most bulbs will rot if they become waterlogged, so good drainage is a must. If you container has no holes in the base it is imperative you make some.
Because if your pot has no drainage holes the soil will oscillate between being very wet and very dry. These conditions are not ideal for plant health. Very wet soil has no air so any actively growing roots will suffocate and die. Very dry soil will dehydrate the bulb and stunt its growth.
Another reason is because bulbs spend part of the year in dormancy, so they have no above ground growth, and are unable to transpire to help reduce extra moisture. So if they have no drainage and the bulb will sit in water and perish.
If you are putting the effort into growing plants in pots it is important you give them the right medium.
Garden soil, no matter how free draining is too dense, it drains poorly in a pot and its compact structure makes it difficult for the roots to get the air they need.
Using a good quality potting mix ensures the perfect balance between good drainage, moisture retention and air; it also has a few nice nutrients to give your plant the best start. Modern potting mixes have been designed for growing plants in pots ensuring good air and moisture content in the pot allowing the plants to thrive.
Potting mixes have got the science right! In addition to providing the perfect drainage, they have applied physics to ensure the right air porosity for roots, and added the best elements to maintain moisture so plants can flourish.
In pots, aeration and drainage, the two elements required for a healthy root system and are directly connected to the size of the soil particles. The perched water table in a coarse medium is lower than that in fine medium. This is why garden soil will never do, because the elements it is made up of are too small, and so will be too compact to allow water to flow through freely and the roots to have access to air so that they can transpire and photosynthesis.
Modern potting mix is perfectly formulated so it is impossible to over water. So any stuff and nonsense you hear about putting stones or crocks in the base of your pot can be ignored, all you will do is reduce the space for root growth, you just need drainage holes, the potting mix will do the rest.
It might be a little bit more expensive but it is most definitely worth it. Good quality potting mixes have got added nutrients and will retain their structure over time. Quality potting mix has the ideal amount of each ingredient. For example, a poor potting mix may contain too much peat moss (when it dries out it shrinks so much it becomes water repellent, so too much may cause failure in plants). Alternatively, poor quality mixes may have too much coir or coconut husk (if this dries out too long it does the opposite of peat moss and becomes super absorbent so your roots may sit in water). Good quality potting has been formulated to avoid such quandaries.
There are many elements that go into the formulation of potting mixes that need to be just right. It is best to use the Australian Standards mark of ticks on the side of the potting mix bags for an indication of quality. To get the ticks the potting mix has to pass rigorous tests.
There are two sets of ticks; the black ticks are for economical regular mixes, these are best for short term plants such as annuals as you only use the mix for one season before you replace it. The premium blends have red ticks which are the best of the best. Use these for long term, or expensive plants you don’t want to lose, it needs less additional fertiliser and lasts well.
Using a good quality mix specific for bulbs is ideal if you have access to it as it contains additional trace elements useful for their growth.
Each variety is a little bit different. The golden rule when planting spring bulbs in the ground is to plant them two to three times the height of the bulb deep. In pots you have a little more freedom, though it is best to keep between these parameters:
1. Bury your bulb at least 2cm deep.
2. Plant no more than three times the height of the bulb deep.
Of course there are always exceptions to the rule, for example, hyacinth and crocus bulbs can be grow half in half out of the soil, but the above guidelines are best followed until you get the hang of it.
Bulbs look best when they are planted close together, you can plant them so close they are cheek to cheek in the pot. If you are using plastic containers, make sure your bulbs don’t touch the edge of the pot as this area can get very hot in sunny conditions and damage the roots. In clay or ceramic pots they are a bit more insulated from the direct sun so can be planted right to the edge.
A little known tip is that some bulbs, such as tulips have a flat side, if you aim to point the flat side outward, this is where the first leaf will sprout from, this will grow down and soften the edge of the pot.
The correct planting depth helps to keep the bulb cool, and provides enough room for root growth.
Bulbs can be planted closely together as their roots will not directly compete and their above ground growth will happily mesh together.
Pour some potting mix into your container, then place the bulbs, pointy end up, at their appropriate level before filling the remainder of the pot with the mix.
Fill the soil level to 2-3 cm below the lip of the pot to allow space for watering.
Yes, you can create lovely effects by combining your potted bulbs in layers.
If you are layering your bulbs, put the tallest, and latest flowering varieties towards the bottom of the pot. Add some more potting mix, ensuring you have covered the first layer of spring bulbs. If your pot is deep enough, you can add a third or fourth layer by repeating the above process. The lower bulbs will easily grow up through the upper plantings. You can even add some annuals to the top of the soil to add interest while you are waiting for the bulbs to come through.
Give the pot a good, slow pour of water to really wet the soil, pour until the water is running out the bottom of the container.
Then you need to keep the soil so the bulb doesn’t struggle with root growth. The roots will be growing well before you see any action above the soil. On average once a week will be fine. You can push your finger into the soil to check if it is moist enough. If you have used a good quality potting mix it will be impossible to over water.
The most common reason bulbs don’t perform in pots is that they have dried out during their growth process. Remember, pots dry out at a much faster rate than garden soil and so need to be watered on a more regular basis.
You do this to keep them cool and out of the way until they begin to grow. Once they begin to grow, bring them into the sun. They need the light to create strong plants. If you grow your bulbs in too much shade they become lanky and unattractive.
Cool conditions are optimal for root growth.
Pots dry out quickly in the sun, so by placing your pot in the shade they will require less water and hence less maintenance.
Once the bulbs begin to grow you should bring them into the sun so the stems grow straight and the foliage has enough light to photosynthesise.
Once your bulbs begin to grow it is a good idea to add some fertiliser to your pot. Be it organic, manmade, liquid or slow release; by adding fertiliser you will improve the longevity of your flowers and get the best possible show.
Newly purchased bulbs will grow and flower with very little fertiliser as they use the reserves stored in the bulb from the previous seasons growth. Adding additional fertiliser will help fortify your bulbs by providing the required nutrients for optimal growth this season and next. Ideally use a specific bulb fertiliser as they contain added trace elements for best growth. Bulbs grow quickly and substantially and so use lots of energy in a short time. Adding fertiliser to bulbs is more important in pots than in the garden because pots have a limited amount of nutrients for them to enjoy. If you have used a good quality potting mix this is less important as they already contain fertilisers.
Don’t forget to keep the pot moist during growth. If the bulb dries out the plant may become stressed which can leave it vulnerable to pests and disease. In hot weather the potting mix can dry out within 12-24 hours.
Add a general purpose fertiliser once the flowers begin to fade, and keep your pot watered until the foliage begins to yellow. The bulbs are about to rest for the next season, adding fertiliser at this time will help the bulb generate a flower for next years show.*
Bulbs grow quickly in a short time and so need a lot of energy. Pre purchased bulbs have all the hard work done for you, they have everything they need to grow and flower that season. Any subsequent seasons it is up to you to provide them with what they need to grow and flower. Once a bulb has finished flowering it diverts its energy back into the bulb and focuses its energies in producing a flower for next year. To do this it requires the additional nutrients in fertilisers.
* We recommend that bulbs such as tulips and hyacinths should only be planted for one year in pots. So once the flowers have finished, you have a couple of choices:
1. After they have been grown in a pot, you can plant the bulbs into the garden to help replenish them. Do this the following autumn (in the pot you will need to add a some fertiliser and keep watering your spring bulbs until the foliage has yellowed, then you can either dig them out and store them somewhere cool and dry, or store them in the pot until it is time for replanting).
2. You can treat them as annuals, throw them on the compost and get some new ones next year. It might sound a bit frivolous, but spring bulbs are inexpensive and with new ones every year you are guaranteed a great show and can try some new varieties and combinations.
There are three main reasons some bulbs, and it is generally those that originate in cool climates, will not succeed in subsequent seasons in a pot:
1. Water – pots dry out easily and you need to be vigilant to ensure it is kept moist at all times.
2. Fertiliser – pots have a limited amount of nutrients and bulbs need a lot of energy in order to grow, if they are unable to access these nutrients they will not have the vigor to facilitate a flower in the next growing season.
3. Soil Temperature – this is usually the one that will get you. If you are attentive enough you can overcome the first two objections, but soil temperature is harder to mitigate. If the soil in the pot becomes too warm it will compromise growth so the bulbs are unlikely to grow large enough to flower the following season. Bulbs such as tulips and hyacinths require cool soil conditions in order to thrive. Bulbs that have originated in warm climates such as Nerines and Freesias are more tolerant of higher soil temperatures and so can be successfully grown for more than one season in a pot.
• Daffodils, in all their shapes and sizes show well. Standard Daffodils grow to around 70cm, so a minimum of a 30cm pot and at least 10 bulbs is ideal. Miniature Daffodils will look especially fabulous in small containers.
• All Tulips will succeed in pots, just remember, the bigger the Tulip, the bigger the pot you will need. For example Monet Tulips grow up to 80cm, so look best in a large, tall container, whereas the Bokassa range with their more compact foliage are handsome in smaller vessels.
• Crocus, these little beauties are very successful in small containers. We have even seen them looking magnificent in tea cups.
• Ranunculus, are suitable, but keep in mind they are heavy feeders, so for the best show you will need to add plenty of fertiliser during their growth. You should choose a big container for these guys and because they are so floriferous you will only need around 3-5 bulbs for a 30cm pot. Now that is a cheap display!
• Hyacinths, these bulbs are well suited to large squat, or low pots. The flowers have gorgeous colour and fragrance. When they are in pots, you can transport them easily to where they can be best enjoyed, be it indoors or out. (When bringing them inside, it is best to wait until they are in bud.)
• Belladonna Lilies, well, is there really anywhere these hardy plants won’t grow!? These hardy sun lovers look fantastic in big pots.
• Nerines, are an easy choice. For Nerines, you can use a squat pot as their foliage appears after the bloom, this will best show off the flowers.
• Cottage Gladioli, the height of their stems and their upright form means you can create a great potted show. Choose a tall pot and plant them close together.
• Grape Hyacinths, these little plants look superb in containers, as their floppy foliage grows it will cascade over the edge, softening the pot. Small pots are best for these little flowers.
• Spring Star Flowers are a great choice, especially for kids. They are so care free they will even cope with a bit of neglect. Like Grape Hyacinths, their foliage will hang over the pot edge. Choose smaller vessels as they only grow to 15cm tall.
• Liliums are a popular choice for potted bulbs. There is a huge range to choose from, such as fragrant Oriental Lilies, colourful Asiatic or classic white Christmas Lilies. You will need at least a 20cm pot for 3 bulbs, and a 30cm pot for 5-6 bulbs.
• Iris reticulata are especially good in small containers.