Parsnips seeds are notoriously difficult to germinate, at best a rate of around 60% is considered to be good. This year our germination rate was down to 20% or less. That left very patchy rows with not many plants.
The big mistake was to use seed from last year. The general advice is to buy fresh parsnip seed each year. There is still time to re-sow with new seed and better still we will do a trial to find the best way to sow for future years.
One answer is to presoak the seeds for a few days before sowing. This can kick them into germinating. When the seeds have germinated and are big enough to handle transfer to small pots. Be very careful not to damage the stems, handle only by the leaves.
There are three small trays sown with the same seed on the same day. Each tray was treated in an identical way.
Tray 1 has 15 seeds sown on their edge. Tray 2 has 15 seeds sown flat on the compost. Tray 3 is for presoaking, there wet capillary matting in the bottom with seeds on top. We will wait and see how long it takes them to sprout compared to seed sown directly into compost. Tray 4 is sown with seeds that had been pres-soaked for 6 days; the top half has 6 seeds on their edge and the bottom has 5 seeds flat. Tray 5 contains beetroot seeds as they also did not do well this year.
When the seeds have germinated, they will be moved into either small fibre pots or home made newspaper pots. (WE will post more on this later.) The bottoms of the fibre pots have been cut across both ways and the four wings produced will be folded out when planted in the ground. This should avoid restricting the tap root. The newspaper pots should quickly disintegrate but hopefully not before planting out.
At the same time, we sowed some beetroot seeds as the sowing in the garden did not do as well as it should. It could have been due to cold, wet soil and the cool start to spring. Never be in a rush to sow or plant if the weather is not right. There can be lots of competition on allotments to get things in early, don’t be dragged along by it.
The trial is using small heated propagator controlled by an electronic thermostat. The temperature is measured by a probe in the compost and set to a maximum of 18.2 C. This is close to the optimum germination temperature of both parsnips and beetroot. See this page for more information.
Do not leave germinated seed in pots for long. As soon as the root hits the bottom of the pot transfer it to the final growing place. It is important that the long tap root is not damaged or constrained or you might get some odd shaped parsnips.
If growing in a greenhouse or on the kitchen windowsill the plants will need to be ‘hardened off’. That means they should be put outside during the day and then brought in at night especially if colder weather is forecast. This should continue for at least a week.
It will take a few weeks to know if presoaking the seeds helps germination or if any particular way of sowing seeds produces better results. Please check back towards the end of May.
Update 17 May 2020
The trial has been stopped. It showed that getting the temperature right and consistent does indeed help germination. The way seeds were planted either on edge of flat made little difference to the germination rates. The key is to ensure that the seed is in good contact with the compost. That means a fine tilth especially for small seeds.
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