What does a seed need to grow?

Friday Apr 22 2016

Ocassionaly we receive a panicked phone call from someone who has waited for weeks only to find that a seed they’ve planted hasn’t germinated. After some troubleshooting, it often turns out that grow lights are the culprit. While light is important for your seeds to grow, there is a difference between growth and germination.  

Most seeds don’t actually need light to germinate – what they do need is moisture and warmth. Germination is the process of waking your plants up and telling them it’s time to burst out of that seed coat and unfurl into the world – it’s time to put down your roots and push out those shoots! It is only “true leaves” that require the energy from light to photosynthesize. So, if you’re starting plants indoors, wait until your seeds start to germinate before putting them under grow lights. (That said, some flower and herb seeds do require light for germination and some vegetable seeds are indifferent to light exposure such as cucumbers and melons.) The trouble with too much light too early is that seeds tend to dry out. If seeds dry out in mid-germination, it’s a lot more difficult to convince them to wake up and start trying to germinate again.

Good quality seeds come equiped with everything they need to germinate – our job is simply to splash them with a good morning cup of moisture and tell them that it’s warm enough to come out and play!

More tips for seed starting:

  • Containers – Make sure trays and pots are clean or sterilized to prevent spreading diseases.
  • Soil medium – When starting seeds ahead, use a light weight seed starting mix or potting soil with plenty of peat moss or coconut fibre (coir) as a base. The Rodale Institute suggests 4 parts screened compost, 2 parts coir, 1 part perlite and 1 part vermiculite. Although, it’s not necessary to make your own soil mix, the key is to find something that is light and fluffly.
  • Temperature – Heat mats are relatively inexpensive and can be found at local hardware stores or nurseries. Typically they are about the size of a flat/tray and use about as much energy as a light bulb, but are quite helpful in providing warmth for emerging seeds.
  • Goldilocks – Think of the old tale of Goldilocks and the Three Bears tasting porrige and sitting on chairs. Your seeds need conditions just like little Goldilocks: not too cold and not too hot, not too wet and not too dry.
  • Nutrients – After about 2-3 weeks your seeds have used up all the food they’ve stored inside and will require nutrients (from you and your soil). Worm castings, seaweed, plant or compost teas and (yes!) human pee are all good sources of organic fertilizer.
  • Strengthening seedlings –  When you start seeds indoors, they aren’t exposed to a whole lot of wind or varied weather conditions. If you find your seedlings getting splindly (weak stems or toppling over), try circulating air around them with a small fan (or a kid who likes blowing out birthday candles). The extra ventilation will not only strengthen your plants, but also help prevent against diseases related to excess moisture.
  • Potting up – Don’t wait too long to transplant your seedlings into bigger pots. This can cause roots to become pot bound or worse, stunt your plants growth. Some plants such as squashes and cucumbers don’t fancy being transplanted so it’s best to start out with larger pots for these seeds.
  • Hardening off – It’s a bit of a shock for plants to go from a controlled environment to the great big outdoors. Get your plants used to being outside by setting them out for a few hours each day and then working your way up to finally transplanting them in the garden.
  • Research, observe and have fun! – Take a look in a good plant book, search online or ask a skilled gardener about anything you are unsure of. When in doubt, try it out! Take a few notes about what your did and build on your experience for next year.


Soil Temperature for Germination

4-15°C

Spinach

5-30°C

Radish

6-24°C

Peas

10-20°C

Celery, Celeriac, Lettuce

10-30°C

Beets, Broccoli, Cabbage, Carrots, Cauliflower, Chard, Greens & Mustards, Onions, Parsnip

12-35°C

Corn

15-25°C

Beans, Brussels Sprouts, Kale, Kohlrabi, Pumpkins

15-30°C

Ground Cherry, Tomatillo, Tomatoes, Turnip & Rutabaga

18-35°C

Cucumber

20-25°C

Leeks

20-30°C

Eggplant, Melon, Peppers, Summer & Winter Squash

 

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