Reverse Season Sowing
I know that one of the biggest challenges we all face is how to keep seedlings from becoming leggy.
Seedlings need up to 16 hours of light each day to prevent from becoming leggy which is more than an adult plant needs to fruit!
If we had lots of money, a grow light system and a big electricity bill wouldn’t be a problem – job done.
However, there is a way of taking advantage of natural light and that is to sow when the days are long.
Last season I sowed a few seeds in August and this is a picture of the result which was taken this week.
Of course the plants have been kept in a sunny window, but the results show that it can be done without grow lights and we can be eating our own tomatoes in February – albeit a modest harvest – unless you have a lot of windowsill space!
Transpiration – Tomato Plants Perspire!
As water vapour is lost from the leaves, water is replaced through the roots.
Without this loss and replacement process, plants wouldn’t be able to absorb the nutrients they need, that are dissolved in water, and taken up through their roots.
If a plant loses moisture from its leaves faster than it can absorb moisture through its roots, the plant wilts.
If a plant absorbs moisture from its roots faster than the leaves can perspire (transpire), fruit will crack and sometimes leaves will appear bubbly/spongy as the pressure inside increases. This often happens when soil that has been allowed to become dry gets a good watering or a heavy downpour of rain!
Moisture loss and availability
If I were a tomato plant, I would probably spend most of my time worrying about the amount of moisture loss from my leaves and the amount of moisture available around my roots!
Keeping the right amount of moisture, or pressure, in a tomato plant is a full-time job. Get it wrong and the plant wilts or the fruit cracks or it doesn’t get enough food and that’s just for starters!
So why do we need to know this stuff … is it important for my plants?
Putting into practice
Understanding how transpiration works helps us to get the most from the circumstances in which a plant is growing. Or even change those circumstances!
There are four conditions that effect the amount a plant transpires.
Transpiration increases as:
- Light increases
- Air flow increases
- Temperature goes up
- Air becomes more dry (less humid)
A sunny day on the windowsill, the leaves will perspire (transpire) more, so a plant needs more water – but we already know that Nick!
However, have you noticed that when you put young plants outside for the first few times in the spring, they are more likely to wilt in the cooler conditions on the patio, than in the warmer temperatures on the windowsill!
Transpiration increases as air flow increases
There is more air movement outside in the garden, so water loss increases from leaves.
One of the problems is, when plants are still young, they don’t have the root area to absorb moisture quickly enough so they wilt.
Transpiration and mineral take up
Reducing the strength of nutrient levels helps too.
Over-feeding young plants on a sunny day may also cause them to wilt because higher levels of minerals in the root area, reduces the amount of water a plant can absorb.
Of course the more leaves a plant has, the more water it will lose when the sun comes out and the breeze blows. A good reason for de-leafing and removing lower leaves.
Temperature and humidity play their part too
As you might imagine, plants lose more moisture in warmer conditions. Dry air will also increase vapour loss from leaves than when it’s humid and the air is already full of moisture.
A greenhouse that isn’t well aerated and contains a lot of condensation will reduce transpiration greatly and growth will slow down.
Also, foliar spraying in humid conditions is much less effective and is more likely to slow growth and increase the chance of disease.
Understanding transpiration (plant perspiration) helps us to grow plants better.
Here’s this week’s mystery object …
Don’t forget to visit the test area tomorrow for some interesting results after just one week!
Regards,
Nick