In the third article based on the talks given at the Seedling Swap in April 2006, Gill Regan shares with us the hard-won secrets of growing bulbs from seed. The many striking photographs that accompanied her talk showed that, after early setbacks, she has clearly discovered a successful formula.
Growing bulbs from seed
by Gill Regan
Sowing a packet of seeds and seeing tiny green shoots followed by leaves and then flowers has always fascinated me, so to produce a large bulb from a seed was a challenge I couldn’t resist, particularly when I was told that it isn’t easy and needs patience. At first I wasn’t very successful but after I altered the compost, things improved.
General purpose potting compost
1 part sterilised soil
1 part fine grade Cambark
1 part peat substitute
1 part perlite (or 5mm grit)
1 part potting compost
1 part perlite
1 part Cambark
Compost for bulb seeds
1 part potting compost with double quantity perlite
Note: with all of these I use Osmacote or liquid feed during the growing season Ref: AGS Bulletin June 2001
I put about 1 cm of gravel at the bottom of each pot, fill the pot with compost, sow the seeds and then top with 1cm of coarse grit. The pots then stand outside, uncovered, all winter in a north-west facing corner. After a cold snap I inspect my pots regularly – and I get such a thrill when seeds germinate.
Even though germination may have taken place, not all plants show growth above ground in the first year. Some lilies, and non-bulbous plants like trilliums, polygonatum and peonies, produce a root only the first spring and require another chilling before a shoot appears the following year.
Patterns of germination
(a) Seeds sown in spring
Germination immediate; flowering within 18 months (eg freesia, tigridia and some lilies).
(b) Seeds sown in autumn
Germination delayed until following spring; chilling during winter breaks dormancy (eg snowdrops, tulips, crocus, fritillaries).
(c) Seeds sown in autumn
Germination starts in spring after chilling; seed produces root below ground then plant becomes dormant in autumn. Growth resumes in second spring, after second chilling in winter; cotyledon appears above ground. This is known as ‘double dormancy’. (eg trilliums, many lilies and other members of the lily family; also a few dicotyledons, such as peonies).
In the spring, after leaf growth starts, I feed all the pots with a dilute solution of general-purpose fertiliser about once a fortnight until the leaves die down.
After germination the seedlings are left in their pots to grow on for at least another year; they are not pricked out. If the pot is very full of seedlings they are repotted when dormant. In some cases I may wait until they start to flower before planting them in the garden. In general, the larger the bulb, the longer you have to wait for it to reach flowering size, and this is where patience is needed. Cardiocrinums often don’t germinate for several years and then take up to seven years to flower – after which the main bulb dies!
Many bulbs need exposure to low temperatures before they will germinate and so are sown in the autumn. If they cannot be sown until the spring, it is probably best to delay sowing until the following autumn. Alternatively, after sowing the seeds in the spring, the pot is put in a plastic bag in the fridge for four to six weeks, or the seeds may be mixed with damp vermiculite and then sown after refrigeration. The exception to this general method is for those seeds which germinate soon after they are sown, such as tigridias and freesias (plants native to warm climates). They must not be sown until the spring and may flower in the same summer.
It is quite common for seeds sown at the same time to germinate over several years. When the seedlings first appear the leaves may be quite different from leaves on the adult plant. When trilliums first germinate a single narrow leaf appears. The pot of trillium seedlings in the picture above shows one plant with typical trillium leaves made up of three leaflets; the rest consist of just a single leaflet. These all germinated a year after the biggest plant. Erythronium leaves don’t show their attractive markings until they are at least three years old, and Lilium martagon seedlings consist of just a single narrow leaf quite unlike the adult rosettes, shown in the picture. In others, such as cyclamen and peonies, the first leaf to appear is a very small version of the adult leaf.
In the beginning I grew bulbs from seed because of the challenge. Then I discovered that it is a way of obtaining plants that are not easy to get hold of, the plants are cheaper and they will be disease-free, which is very important, particularly with lilies. It is true that it may take several years to flower, but if you sow seeds every year, then every year you will have some that will reach flowering size. So get hold of the seed lists, choose your seeds and start sowing this year.