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Tuesday, July 16, 2024
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Raising from seed can’t be that hard

I was out and about the hill suburbs of Tawa early on Sunday morning, when I noticed a pure white King protea, P. cynaroides with a few blooms open and several old flower heads.

I stopped to look at the flower and sneakily took a few seeds from the spent blooms. I love growing plants from seed, and although I have never tried proteas. I thought “How hard can they be?”

A quick romp through Google tells me that they can be quite tricky. Some sources point out that this species [along with many others that evolved to grow in very dry fire-prone areas] needs “wildfire smoke” to germinate, while others point out the troubles you are likely to encounter with fungus diseases.

Once I read about dipping in a hydrogen peroxide solution and using “smoke primer disks”, I realised that my desire to grow this wonderful shrub from seed was quickly fading, and I abandoned the idea.

As someone who once earned their income by growing tens of thousands of plants from seed, it is not surprising that I should have retained an interest in raising plants that way. However, almost all the plants that are grown from seed in nurseries have been selected for reliable and uniform germination – very few common vegetables need any special kind of treatment, and the same applies to most flowering bedding plants.

Sometimes there can be slightly tricky problems. Some colours of several flowering plants we grew germinated and prospered at different levels, and that posed a strange problem for us. The staff were used to grading plants as they pricked them out – all the biggest plants into one punnet, the smaller ones into another. That meant that the “mixed” colours the customer wanted were likely to be destroyed, with the dominant seedlings all being the same colour.

Dierma seed germinates well.

Away from the more usual plants, some species do need special pre-sowing treatment. Many from colder climes require a period of chilling before they will germinate. At one time, the Head Gardener had to put up with containers of eucalyptus seeds in the refrigerator for some weeks. However, the most extreme case I know of is a peony species that requires two chillings. After the first one, the root appears, but it takes another chilling before the leaves will appear.

Other plants have chemicals to stop the plants from germinating as they fall in the autumn, presumably so the seeds will wait for the prime spring growing season before they sprout. Gardeners can subvert that process by rinsing the seeds several times. The Pacific Coast irises I grow from seed have this mechanism built it in, so many growers have adopted an unusual technique to solve this problem – they wrap the seed in cloth, then place the packets in the toilet cistern for a few weeks, the constant flushing removing the chemicals.

In my glasshouse now, I have quite a few seed-grown plants, some with tricky requirements. I have been crossing pink and white lapageria for some years now, hoping for a lighter pink form. There have been one or two very pale pink, but not the result I have been looking for. The seed for these need to be sown almost as soon as they are ripe – if they dry out, they are very difficult to germinate.

I also have some angel’s fishing rod, Dierma species, and some velthemia from seed. These are both South African bulbs and germinate readily – a pot of the former looks like the proverbial hair on the dog’s back. Although both are easily divided, it is fun to grow from seed to see if there is any variation.

Newly germinated lapageria seedlings.

I also have just one Camellia granthamiana in a pot. This is a rare autumn flowering species that I noticed in the Masterton garden, having misidentified it as a gordonia [an autumn flowering camellia relative] for years! I pinched a seed pod from the tree, and although three or four tried to grow, only one succeeded.

In general, there are a few simple rules to growing common plants from seed. The first is to make sure the plants are not sown too deep – as a rule seed should be planted to a depth that corresponds with its size. Very fine seed [begonias, for example] should be sown on top of the mix, while most will just need a sprinkle of fine mix over the top.

Use a seed sowing mix – soil tends to have diseases that can cause damping off – and make sure it is damp before sowing the seeds. You can then cover them lightly and gently water the seed again. Most seeds will germinate best if warm [bottom heat is great if you have a heat pad] but make sure the seed mix never dries out as that can mean sudden death.

Roger Parker
Roger Parker
Roger Parker is the Times-Age news director. In the Venn-diagram of his two great loves, news and sport, sports news is the sweet spot.

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