How to Water Seeds and Seedlings, Fully Explained

by Jim O’Donnell

Water is one of the vital elements when starting plants from seed. Too much water and your seeds will drown or rot. Too little and they will either fail to germinate or die once they do.

If you are starting your vegetable garden from seed, you have two choices. One, you can start your seeds indoors and then plant them outside as seedlings several weeks later, or you can direct seed into your garden.

There are a number of good reasons to start seeds early indoors. Most importantly, you get ahead of the growing season. This is especially important if you live in a place with a short growing season. Another advantage is that you can tightly control the ideal growing conditions: temperature, moisture, sunlight, etc. A third advantage is cooling that early spring itch to get outside and get something in the ground!

The best candidates for early starts are things like broccoli, cabbage, cauliflower, celery, eggplant, leeks, onions, parsley, peppers, and tomatoes. Root crops, like beets and carrots do not like to be transplanted and are best sown directly into the garden. Corn and peas are other things that do not take well to a transplanting.

To germinate your seeds you can do one of two things:

1. You can moisten a paper towel, place the seeds in the middle of the paper towel and place it on the window sill in the sunlight.

2. Alternately, you can fill small sections of a seed starting tray with a soil mixture and plant the seeds into the mixture about 1 inch deep. Then water lightly.

Either way, you don’t want the seeds sitting in water. You want to have the soil or paper towel moist but not soaked. Let the soil mix dry out just a bit, but not completely, before wetting again. I use a spray bottle to keep my starting mixture moist. The key is good drainage. Make sure that excess water has a way to drain away from the seeds. There are seed starting systems available that work via a capillary system. This keeps your soil at the right moisture level with no work from you but I find the spray bottle method pretty simple.

If you cover your seeds with some loose plastic you will create a mini-greenhouse environment that will hold in both heat and moisture. You will need to get air to the seeds so remove the plastic every once in a while so that you don’t get mold formation that can ruin your seeds.

After a few days, two small leaves will appear once your seedlings begin poking through the soil and unfurling. Again, keep the soil moist as the seedling begins to take off.

As the days warm and lengthen you will begin taking your seedlings outdoors to “harden off”. That is, to get them used to being outside by putting them out for portions of the day (you will still be bringing them inside at night). Be careful here. The sun and spring winds can dry out that delicate soil in a heartbeat.

When the day comes that you are ready to plant your seedlings into the garden, water them well before the transplant. Once they are in the garden, water them again very well. Finally, to avoid drying out your seedlings try not to transplant during the hottest, sunniest part of the day.

Basic Watering Tips for Starts

Not every plant has the same needs when it comes to watering, but there are some basic rules you should follow according to a website on How to Grow Plants Indoors:

– Wet the soil thoroughly, and the water should be able to drain out of the bottom of the pot. How much you water, and how often purely depends on the type of plant that you are dealing with, so read the seeds or ask the person selling you the plant, how much water does this plant require.
– Now, don’t over water, that’s probably what kills most plants. If you have too wet of a soil constantly it will lead to problems with the roots. You’ll notice that the leaves will become yellow, that’s because there is not enough oxygen in the soil because it is too wet.
– When watering the plants, try to use water that is the same temperature as the room. This will insure that the plant doesn’t have any shock from too cold or hot water.

Source: http://www.webterrace.com/garden/tips.htm

Key Points About Watering Seeds and Transplanting Seedlings

• Monitor moisture: Check the moisture levels of the paper towel or seed starting mix daily to ensure it remains consistently moist but not waterlogged.
  
• Spray bottle technique: Use a spray bottle to gently mist the seed starting mix, preventing it from becoming too wet or too dry.
  
• Ventilation: When using plastic to create a mini-greenhouse environment, make sure to vent it periodically to prevent mold growth and provide fresh air.
  
• Gradual hardening off: Increase outdoor exposure for seedlings gradually to help them acclimate to outdoor conditions without shock.
  
• Protect from wind: Place seedlings in a sheltered area during the hardening off process to avoid wind damage or excessive drying.
  
• Pre-watering before transplant: Ensure seedlings are well-watered before transplanting to minimize stress and help them establish in the garden more easily.
  
• Transplant timing: Transplant seedlings during cooler parts of the day, such as early morning or late afternoon, to avoid heat stress and reduce moisture loss.
  
• Mulching: Apply a layer of mulch around newly transplanted seedlings to help retain moisture in the soil and protect them from drying out too quickly.
  
• Monitor post-transplant: Keep a close eye on transplanted seedlings, watering them as needed to maintain soil moisture while they establish themselves in their new environment.

Seed Starting and Transplanting Advice for Popular Vegetables

No.	Plant Type	Ideal Germination Temp (°F)	Watering Frequency	Transplanting Difficulty	Notes
1	Tomatoes	70-80	Keep soil moist	Easy	Sensitive to frost
2	Bell Peppers	70-80	Keep soil moist	Easy	Sensitive to frost
3	Cucumbers	70-85	Keep soil moist	Moderate	Susceptible to transplant shock
4	Zucchini	70-85	Keep soil moist	Moderate	Susceptible to transplant shock
5	Carrots	45-85	Keep soil moist	Not recommended	Direct sow in the garden
6	Lettuce	40-75	Keep soil moist	Easy	Transplant in cooler weather
7	Spinach	45-75	Keep soil moist	Easy	Transplant in cooler weather
8	Green Beans	60-85	Keep soil moist	Not recommended	Direct sow in the garden
9	Peas	40-75	Keep soil moist	Moderate	Prefer cooler weather
10	Onions	50-75	Keep soil moist	Easy	Transplant as seedlings
11	Beets	50-85	Keep soil moist	Not recommended	Direct sow in the garden
12	Radishes	45-85	Keep soil moist	Not recommended	Direct sow in the garden
13	Swiss Chard	50-85	Keep soil moist	Easy	Can tolerate some frost
14	Broccoli	45-85	Keep soil moist	Easy	Tolerates cool weather
15	Cauliflower	45-85	Keep soil moist	Easy	Tolerates cool weather
16	Cabbage	45-85	Keep soil moist	Easy	Tolerates cool weather
17	Brussels Sprouts	45-85	Keep soil moist	Easy	Tolerates cool weather
18	Eggplant	70-90	Keep soil moist	Easy	Sensitive to frost
19	Celery	60-70	Keep soil moist	Moderate	Requires consistent moisture
20	Kale	45-85	Keep soil moist	Easy	Tolerates cool weather
21	Leeks	45-85	Keep soil moist	Easy	Tolerates cool weather
22	Parsley	50-85	Keep soil moist	Easy	Can tolerate some frost
23	Turnips	45-85	Keep soil moist	Not recommended	Direct sow

Common Questions and Answers About How to Water Seeds and Seedlings

by Erin Marissa Russell

Can an overwatered plant be saved?

Overwatering can damage and even kill plants, but as long as you take action before it’s too late, you can save an overwatered plant. You can tell a plant has been overwatered when the leaf color begins to fade to pale green or yellow, algae or mold appears in the pot, a foul odor is present, the plant begins to wilt, or new growth stops even though you’ve been watering the plant. First, make sure the container your plant grows in has drainage holes. You can read about how to add holes for drainage in this article.

Don’t give the plant any more water until the soil is dry. You can check by sticking your finger into a hole in the soil, and if soil clings to your skin, it’s still moist. The top of an overwatered plant is sensitive to sun, so move the plant into the shade to protect its foliage from further damage. Using a spade or your hand, tap the sides of the container to loosen the soil. Tilt the container and gently slide the plant out of the pot. Use your hands to shake the dirt off the plant’s roots so you can examine them.

Discard the soil; once a plant’s been overwatered, it may contain mold, algae, or transmit root rot. Use clean, sterilized gardening shears to snip away any slimy or discolored roots that are turning brown and discard them. Keep roots that are pale, firm, and healthy. Sterilize your shears again, then trim away any dead or damaged leaves and foliage from the plant. Repot the plant into a new container with fresh potting soil, and water it only when the soil has dried out. Test the same way, by sticking a finger into the soil and waiting until no soil clings to your skin,

Can you overwater seeds?

Yes, it’s possible to overwater seeds, which can cause them to be washed away from where they’re planted or encourage the growth of mold, alage, or fungi, or cause rot. Avoid overwatering by planting seeds exactly as deep as the instructions specify. Give seeds planted in shady areas (like under trees) less water than those planted in the sun. If you know you’re prone to overwatering, try using a mister or capillary mat. Allow the soil to dry out before you water it again, which you can check by sticking your finger into the soil. If dirt clings to your skin, the soil is still moist and doesn’t need water.

Do seeds drown?

It’s possible to drown seeds that you are soaking before planting, and drowned seeds will not germinate. Soak seeds for 12 to 24 hours—no more than 48 hours, or drowning becomes a concern.

Do you water seeds during germination?

Keep seeds damp before germination, but not too wet. This usually means watering once per day. However, if you’re using a seed starting tray, the plastic cover may be sufficient to keep the soil moist, or you can cover your container with plastic wrap. Check frequently to make sure this is the case. Never allow the soil to dry out completely, even before germination occurs. Capillary mats can take the guesswork out of the moisture level.

Do you water seeds every day?

Yes, seeds normally need to be watered at least once per day to keep the soil moist, not permitting it to dry out. In especially warm climates (or depending on your soil or garden setup), you may need to water more than once per day. Check on your seeds or seedlings frequently to make sure they have plenty of water.

How can you make seeds germinate faster?

There are a few steps you can take to make seeds germinate faster. Soak seeds in warm distilled water for 24 hours before sowing to soften the seed coat and speed up germination. You can also use a heat mat to keep seeds in the best temperature range to help them germinate quickly. Using the plastic cover of a seed tray or covering your seed container with plastic wrap can also help germination along by keeping things moist. If your seed package says they need scarification, stratification, or cold treatment before germination, follow one of the methods to help germination in this article.

How do you start seeds in a Ziploc bag?

To start seeds in a Ziploc bag, first soak them overnight in water, then drain them. Fold a damp paper towel, and insert it into the Ziploc bag. Add your seeds between the towel and one side of the plastic bag. Find a sunny windowsill to place the Ziploc bag. Seeds should begin sprouting in just 24 hours and be fully sprouted within three days to one week.

How moist should soil be for seedlings?

You want seedlings to be kept moist but not wet and never allowed to dry out completely. This most often translates to watering the soil for your seedlings at least once per day, if not more often. A spray bottle is a good way to water your seedlings and keep the soil moist without letting it get too wet. It’s important for your setup to include drainage so that excess water can drain away from your seedlings. A capillary mat is a good watering method that takes the guesswork out of how wet your seedlings should be. You can learn to make your own capillary mat or purchase one. You can also water from the bottom, letting your seedlings draw water up through the drainage holes of the container. Check moisture at the top every 10 minutes, and remove the water source when the top is damp.

How much should you water seedlings?

The soil seedlings grow in needs to be moist or wet but not too damp, and it should never dry out between waterings. To achieve this, you should check on your seeds more than once per day, and you’ll probably need to water them at least daily. You can make things easier and keep the soil moist by covering your setup with plastic wrap (if it does not have a plastic lid) or by watering from the bottom, so water comes up through the drainage holes as needed. Check moisture of the soil’s surface every 10 minutes, and when the top of the soil feels moist, you can remove the water.

How do I know if my seedlings need water?

Seedlings need water when the surface of the soil begins to become dry, but the soil should never be allowed to dry out completely. Check the moisture level by touching it with your finger at least twice per day, and you’ll probably need to water at least daily. You can use a spray bottle to help keep things moist but prevent getting the soil overly wet.

How do you start a paper towel with seeds?

Wet a paper towel, then wring out the water so the towel is damp but not wet. Space your seeds out evenly across this towel, then cover it with another moist paper towel. You may choose to use a four-inch square so you don’t have to fold the towel, or you can fold so it fits inside of a Ziploc bag. Place your towels with the seeds inside into a Ziploc bag and keep on a sunny windowsill. Seeds will start sprouting within 24 hours and can take three days to a week to fully germinate.

Is it OK to plant seeds in the rain?

You may plant seeds before a light rain so you don’t need to water them, but too heavy of a rain can wash them away. If the rain is a light shower, you can choose to plant seeds in the rain. Beware of planting seeds during heavy rains that can wash the seeds out of where you’ve sown them.

What seeds should be soaked before planting?

The following seeds benefit from being soaked for 24 hours before planting: Large seeds, wrinkled seeds, and seeds with hard coats. These include beans, corn, lupine, nasturtium, peas, pumpkins, squash, sunflower, and sweet pea.

What vegetable seeds should I start indoors?

Starting seeds indoors helps you get a jump on the spring garden when the weather isn’t yet warm enough, but some plants are a better option than others for starting indoors. Vegetable seeds that can be started indoors and easily transplant include: broccoli, Brussels sprouts, cabbage, cauliflower, eggplant, kale, lettuce, onion, okra, pepper, sweet potato, and tomato. Seeds you can start indoors but must be careful transplanting include: Celery, chard, cucumber, melon, peas, pumpkin, spinach, and squash. Do not start these seeds indoors: Bean, beet, carrot, corn.

Why do seedlings die?

Many different factors can cause seedlings to die. The soil, temperature, and moisture level all must match the plant’s preferences to keep seedlings thriving. Once seeds have germinated, light and air circulation come into play. Most seedlings die due to a mismatch in their care needs and one of these factors.

Why do some seeds fail to germinate?

There is a broad range of possible causes when seeds fail to germinate. Seeds may not sprout if they’re expired or if they’re less than fresh because they weren’t properly stored. Seeds that are sown directly in the ground may not come up if eaten by birds and other wildlife or if they’ve been washed away by rains. Seeds that aren’t planted at the depth required by that particular plant may fail to come up. Moisture levels and temperature outside the range your seeds need can also prevent them from coming up. If seeds are sown at the wrong time of year or the weather is not what’s expected, the result can be seeds that don’t sprout. Soil needs to be rich, loose, and well draining for seeds to come up, as well as within the appropriate range of pH levels. If you aren’t sure of your soil’s pH level, this article has instructions for testing soil pH level to find out.

Want to learn more about watering seeds and seedlings?

Washington State University Extension covers Why Did My Seedling Die?

Farmers’ Almanac covers Best Weather for Gardening Tasks

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Jim O’Donnell gardens in the mountains of northern New Mexico. A certified permaculture designer and ecological restoration specialist, Jim’s first book Notes for the Aurora Society was published in 2009.