Basic Guide to Hybridizing

Doesn’t it sound interesting to be able to create new plants all by yourself? Varieties that never have existed before. Everyone can do it as long as you’re patient and have basic knowledge and tools. 

Background

Most people have probably taken cuttings of their plants. This is an easy way to propagate your plants. It will however always result in a clone of the same plant you took the cutting from.

The only way to create a new plant with unique characteristics is by sowing seeds. The seeds are the result of the genetics from both parent plants scrambled into a new plant. Also when self pollinating hybrid plants, this is a way of scrambling the genetics and get new variation in the offspring.

Hybridization, or cross pollination is the act of knowingly choosing pollen from one plant and using it to pollinate another. The resulting seeds when sown will result in hybrid seedlings. These seedlings can then be grown, evaluated and possibly named if they are unique and have good enough qualities.

How to

Cross Pollination

To cross pollinate, you’ll need:

  • two different plants flowering at the same time. Preferably two closely related hybrids, or species in the same genus.
  • a tool to bring pollen from one flower to apply it to another. There are many options like thin brushes, cotton swabs, toothpicks etc. (personally I prefer a size 2 aquarelle brush)
  • a tag, a piece of thread or some acrylic paint to mark your cross pollinated flowers.
  • a small pair of scissors can sometimes be of help when working with species that has narrow flower tubes (like Achimenes or Streptocarpus). These flowers get a lot easier to reach both the pollen and the stigma on if the flower is carefully cut open.

When cross pollinating two plants. You’ll want the seed parent (the plant that recieves the pollen, which will produce the seed capsule) to have a flower that’s been open for a couple of days. In the Gesneriaceae family it’s very common for the flower to not be able to recieve pollen until the flower has been open for a while. In nature this is to reduce the risk of self pollination.

  1. Use your tool to pick up some pollen from the pollen parent’s anthers and apply it to the stigma of the seed parent flower. Be generous with the pollen and carefully rub it over the whole stigma.
  2. Mark the pollinated flower in a way that you can save information about this cross pollination. This will help you keep track of this specific cross. Personally I like to cut a small platic tag into a clip on tag. On this I write the date of pollination and the pollen parents name. Others prefer to either knot a piece of thread carefully around the pollinated flower and place a separate tag in the pot with the name of the pollen parent and the date. Yet another method is to use acrylic paint and put a dab of the paint onto a calyx lobe of the pollinated flower. Using different colours you can then keep track of which pollen parent you’ve used on which flower. Using a tag with the colour codes and dates kept in the pot.

-Special case regarding Kohleria– 

It’s very common for Kohleria cultivars to be pollen sterile. That means you’ll need to get at least one plant that is pollen fertile to successfully make a cross pollination. To learn which kohlerias are pollen fertile, you can search for “fertile” in my List of Kohleria Cultivars page. Pollen sterility is a trait that gets passed on as long as the seed parent got it. That means the only way to get pollen producing new hybrids is by crossing two pollen fertile plants.

Sowing the Hybrid Seeds

To sow gesneriad seeds you’ll need:

  • a transparent container, preferably with a lid but you can also use plastic cling wrap to cover it 
  • substrate. I prefer a good quality peat based potting soil but there are many options.
  • a spray bottle
  • a piece of paper
  • tags, to tag the name of what you have sown, and any further information about the cross.
  • grow lights or a bright spot without direct sunlight

Once the pollination is done and successful, it will take anywhere from a month to six months for the seed capsule to mature fully depending on species. Once the pod is fully mature (in many gesneriads the capsule dries up by itself, but there are some species that produces berries like Columnea etc.) you can either sow the seeds directly, or save them until later. Gesneriad seeds generally keep viable for a long time. The seeds are minute so be careful when handling them. Using a big white paper to work on will help you see the seeds if you where to spill any. It’s good to know gesneriad seeds are light germinating, meaning they need to be sown on the surface of the soil and kept in a bright spot to germinate.

  1. Fill your container with your substrate, and only gently pack it down to a flat surface so the minute seeds don’t end up falling down deep in the soil later. Mist the substrate so it gets moist but not wet and waterlogged. 
  2. Crease a piece of paper and open the paper up again. Distribute the seeds you want to sow on this paper, then gently hold the creased paper “like a taco”. Use the paper as a guide and gently tap out the seeds onto the moist substrate.
  3. Mist gently again and put the lid on the container.
  4. Put the container in a bright spot sheltered from direct sunlight, or under grow lights. Wait for the seedligs to germinate.

Growing the Seedlings to Flowering Size

To grow the small seedlings into large flowering plant, you’ll need:

  • the sown seedlings
  • a toothpick, skewer or similar
  • a small pair of scissors
  • a number of pots in different sizes
  • soil
  • fertilizer

Once the seedlings have germinated and got about three pairs of leaves you can start transplanting them. Gesneriads usually get stimulated to grow quicker if you transplant them often. The first transplant can be to a similar container you sowed the seeds in. Once they’ve then grown even bigger it’s time for them to get small individual pots. With each transplant from here on you can remove the lowest pairs of leaves and plant the seedlings deeper in the soil. This will promote a quicker growth of the root system and the plant will grow faster. I sometimes use cling wrap to cover the seedlings when first transplanted from the container into a pot, to minimize the risk of shock due to changed humidity for the seedlings.

Keep on growing, transplanting them regularly and give them regular additions of fertilizer to grow well. Depending on the species it can take around 3 months to a couple of years from sowing to get flowering hybrid seedlings.