What triggers growth stages in your plants? Two types of cues work together to push your plants from one phase to the next. Outside signals like day length and temperature tell your plants what season it is. Inside signals from hormones tell them when they are ready to move on to the next stage.
I watched this play out in my garden when my lettuce suddenly bolted last spring. The plants had been making leaves for weeks with no sign of flowers anywhere. Then the days got longer in late May and everything changed. Within a week every lettuce plant shot up a tall stalk and started blooming. The longer days had flipped a switch inside them.
When I first tried to rebloom a poinsettia after the holidays, I failed because my porch light kept it from sensing long nights. These plants need long nights to turn their leaves red and make flowers. The next year I put it in a dark closet each evening for weeks. That worked to trigger its color change right before the holidays came again.
Your plants sense day length using proteins called phytochromes in their cells. These proteins track how long darkness lasts each night for your plants. When nights hit a certain length, phytochromes send signals that trigger flowering. This is why some of your plants bloom in spring while others bloom in fall based on growth stage signals.
Temperature also serves as a trigger for many plant stage transitions in your garden. Some of your plants need a cold period before they can flower at all. This is called vernalization and it affects things like tulips, garlic, and winter wheat. Without enough cold weeks, these plants stay stuck in vegetative mode.
Hormones carry out the actual changes inside your plants as they grow. Auxins control where new growth happens and how your stems bend toward light. Cytokinins push cell division and keep your leaves green longer on the plant. Gibberellins trigger stem growth and flowering in many species you might grow.
Different plants use different triggers to move through their stages in your garden. Short-day plants like chrysanthemums need nights longer than 12 hours to start flowering. Long-day plants like spinach flower when nights get shorter than 10 hours in late spring. Day-neutral plants ignore day length and flower when they reach a certain size.
You can use this knowledge to control when your plants move through stages. Keep your lettuce from bolting by growing it in partial shade during long summer days. Force a poinsettia to rebloom by giving it 14 hours of darkness each night for six weeks in fall. Trick your spinach into staying leafy by blocking some afternoon sun from the bed.
Pinching off flower buds keeps your plants in vegetative mode longer if you want more leaves. This works great for your basil and many other herbs you grow for leaves. For your fruiting crops, you want the opposite effect. Make sure they get the right growth stage signals to trigger blooming at the right time for a good harvest.
Read the full article: 6 Plant Growth Stages Explained Simply
