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Use warming mats to heat your seeds

Rubberised pads are a cheap, compact alternative to a greenhouse

Greenhouse effect: raising soil temperature using a warming pad. Photograph: Biogreen

Greenhouse effect: raising soil temperature using a warming pad. Photograph: Biogreen

A ll my current fantasies are about greenhouses. I am tortured by emails from fancy manufacturers seducing me with modern glass cubes and cute-as-a-button wooden structures. Imagine standing in a greenhouse, I think, as I play Tetris with seedling trays on countertops at home. What starts off on windowsills quickly sprawls on to any flat surface.

So, for a fraction of the price of a greenhouse, I’ve been trying out BioGreen’s rubberised warming pads as a new solution. You sit the seed trays on flat plastic mats that heat the soil to 5-10 degrees warmer than the ambient temperature. If you stick a bit of recycled polystyrene underneath, and add in some cheap LED grow lights with a timer, you’ve got a pretty good propagation unit.

These warming pads are efficient. I’ve maintained a soil temperature of 22C with no problem, which is perfect for tomatoes, parsley, onions, cabbages, basil, beets, swiss chard… The list goes on; it truly is the sweet spot for speedy germination.

However, there are a few things that like the dial turned up just a bit more: chilli peppers, sweet peppers and aubergines, as well as some of the more tropical herbs, such as holy basil, germinate best between 25-28C. By chance, I found that if you use the sort of insulation board common in roofing – the stuff that’s covered in tin foil – then you can easily bump up that temperature. I’m genuinely excited about this; it’s not easy to find a cheap set-up that will heat that consistently.

You’ll need a propagation lid, preferably with a vent, as the first stage of germination is reliant on moisture, and if the soil around the seed dries out after the initial watering this can be fatal. However, once the seedlings are up, if conditions are too humid, with poor air circulation, you can get damping-off disease – which causes emerging seedlings to collapse, often covered in white mould – and other moulds. That little vent on the top is surprisingly effective. If you do find yourself with damping off, try watering with a strong brew of cold camomile tea, which is naturally antifungal.

Rubberised pads are a cheap, compact alternative to a greenhouse

Influence of heat shock on seed germination of plants from regularly burnt savanna woodlands and grasslands in Ethiopia

Abstract

The effect of heat shock on the germination of seeds of 21 plant speciesfrom fire-prone wooded savanna ecosystems in western Ethiopia was analysed inorder to examine the possible implications of fire upon plant regenerationafterthis disturbance. Seeds were subjected to 6 different heat intensities (20, 60,90, 120, 150 and 200 °C) for 1 or 5 minutes, in ordertosimulate the situation in the upper soil layers or on the soil surface duringfires. Germination tests were carried out in pots in a greenhouse over 20weeks.After 9 weeks no more seedlings emerged. There was wide interspecific variationin the responses of seeds to the different treatments. In all species,germination was significantly affected by the temperature treatment level.Shortexposure of seeds to high temperatures generally stimulated germination whereasprolonged exposure reduced seed germination. However, some species eventolerated 5 min treatment at 200 °C. Seedheat resistance was positively correlated with seed length and mass among thespecies. Hence, production of large seeds with protective tissues promotessurvival in fire-prone savanna areas. Also, the seeds of some species showedboth a low and a high temperature optimum which ensures that at least someseedsgerminate in the absence of fire, but also that viable seeds still remain ifsubsequent late fires kill emerging seedlings. Frequent and light burning inwooded savanna grasslands seems to stimulate and enhance germination of most ofthe studied plant species.

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The effect of heat shock on the germination of seeds of 21 plant speciesfrom fire-prone wooded savanna ecosystems in western Ethiopia was analysed inorder