How to Grow Marigold Indoors

How bright should your grow light be? 

Marigold plants need the equivalent of 5+ hours of direct sunlight [DLI of 15+ mol/m²/day] to grow their best. In order to provide an equivalent amount with a grow light, it needs to be pretty bright! The 24W Sansi bulb should be placed 6 inches away from the top of the plant. This will give your PPFD (the standard measure of brightness) of 500 μmol/m²/s.

How many hours per day do your Marigold plants need under a grow light?

Marigold plants are known as “short-day,” meaning they’ll develop faster if they sense over 12 hours of darkness. We want them to progress into flowering as soon as possible, so we recommend setting up a timer to leave it on for only 10 hours per day. This also makes it easy for you to have your own marigold plant indoors.

Marigold Plants Grow Faster in Warmer Temps

Marigold plants are called “warm-weather crops” and will speed up their metabolism when temperatures are warmer. On the other hand, if things get too hot they’ll wilt and become prone to disease. Ideal temperatures are around 65°F but anything between 50 and 70°F grows well.

Week 1-2: Check for Sprouts

You could see seedlings in as little as 5 days (though 7 days is more typical). If it’s been 10 days and you still don’t have any sprouts, it’s likely that your setup is too cold.

Week 3: Thin Your Seedlings

Thin your planter to only have 1 seedling per site –  leaving the largest plant. If you are using the reccomended planter (at least 4″ / 1 pint) this will mean you’ve got 1 plant after thinning.  By getting rid of the smaller seedlings, you’re allowing the biggest and strongest one to flourish by reducing its competition for water, food, and space. 

If your seedlings are under 1 inch, stretching out, or folding over, it’s likely that they don’t have quite enough light.

Month 2+: How to Harvest Marigold

Pick flowers right as they open to encourage more flowers to grow. If you let flowers go to seed on the plant it will start to end their life cycle so you should “deadhead” (remove the old flowers) to prolong the flowering season. If you fall behind, you can cut the plant by one-third which produces a second flush of leaves and flowers.

Year 1: End of Life

You can prolong your marigold’s life by pruning it and removing flowers before they have a chance to go to seed, but eventually, it will die. At this time is best to clear the plant and start over.

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The right supplies can take the guesswork out of caring for your plants – and turn care from a daily to weekly routine. Through our grow tests, we’ve found these products to produce the best indoor Marigold (and also have simple maintenance).  Plants are adaptable and can grow in many different conditions, so they are by no means necessary if you already have other supplies.

Best Containers for Marigold: Ceramic Self Watering Planters

Plants thrive on consistent moisture but can suffer if they’re waterlogged. A semi-porous ceramic self regulates ideal conditions. Our favorite is the COSWIP planter. Runner up is XS Self Watering Planter by Wet Pot.

Best Soil for Marigold: Standard Potting Mix

Marigold likes a rich and moist root zone – so you are best off with a standard potting mix – we like this Organic Mix by Espoma. 

Best Nutrients for Marigold: Balanced Blend followed by Vegetable Blend

Marigold likes to start with nutrients that are equal parts nitrogen, phosphorus, and potassium (with NPK numbers like 10-10-10). For this Balanced Blend we recommend: Dr Earth All Purpose

Once they are growing, it’s better to use plant food that is high in phosphorus and low in nitrogen (with NPK numbers like 4-10-6). For this Vegetable Blend, we recommend: Joyful Dirt Tomato & Herb

Best Light for Marigold: DIY or Soltech

There is a very small chance that you have the bright windows needed to grow these without a grow light. If you are looking for a higher-end option – we love the Aspect Light by Soltech. For a more affordable option, a DIY setup using a 24W Screw-in Bulb by Sansi with a Clamp Light and Mechanical Timer works well too.  Check out our complete guide on a DIY setup for less than $40 or our buying guide for screw in bulbs.