Starting Seeds

Choosing What to Grow

Before you order seeds in the early spring, draw up a quick map of your garden space on graph paper. Use the spacing guidelines for each type of plant, which can be found in reference books or on the seed packet itself. Then sketch the arrangement of the vegetables and herbs that you’d like to grow. This will help you visualize how many different types of plants you can fit in your space and decide which seeds you would like to order.

When it comes time to order seeds, consider combining your order with a neighbor or fellow gardener. It will save you money on shipping, and if you have a small space but wish to try many different varieties, buying together will allow you to share and try more varieties. Also look for seed swap events, where you can meet local gardeners, share seeds, and get advice on the best varieties for your area.

What You Will Need

You can grow seeds in many different types of containers, and many seeds really should just be direct seeded out in the garden. For starting seeds indoords, many people use seed-starting trays with cellpack inserts, and those work very well for the purpose. These are available from most garden-supply stores. Larger seedlings, such as pumpkins, do best if started in three-inch pots, as they need more space to grow well. Peat pots or peat pellets, though readily available and purchased widely, don't contain any nutrients are dry out rapidly, so can be problematic. If you like to recycle, good planting containers can also be made from old milk cartons. Just cut them down to be about three inches in height, and be sure to punch drainage holes in the bottom. If you re-use seed starting trays or containers from last year, wash them first, making sure to rinse them well. You can use a solution of distilled white vinegar for this purpose. Then sanitize by dipping them in a 10% bleach solution (1 part bleach to 10 parts water) and allowing to air dry.

Generally, it is best to use a soilless seed starting mix that doesn’t contain any fertilizer to grow seedlings. It is not recommended that you re-use potting soil or use soil from your garden for starting seedlings, because these may contain bacteria or fungal organisms that might be harmful to your plants. It is also recommended that you avoid those that contain chemical fertilizers. Using too much fertilizer can burn your seedlings. (If you are interested in making your own seed starting mix instead of using a prepackaged one, there are many gardening books that give direction on this subject, see References.)

If you have a greenhouse, you will not have to worry about supplemental lighting. However, to grow seedlings most successfully indoors, you may want to invest in a lighting system. Generally, “shop lights” work best for this. This is a type of lighting fixture that features two florescent bulbs side by side in a metal hood. Good results have been obtained from using two 40 watt florescent bulbs, one cool and one warm, together. Suspend the lighting fixture just two inches above the tops of the seedlings, as they need quite a bit of light. If you notice your seedlings are getting very tall and spindly, then the light is too far away or not bright enough. Your seedlings need 12 to 16 hours of light a day, and periods of darkness.

If you have a lot of plants, a watering can may be helpful. However, a simple plastic cup with small holes poked in the bottom is a good, gentle way to water your seedlings indoors.

To label your seedlings, popsicle sticks or plastic labels can be useful. A permanent marker can be used, but a grease pencil will also work as it does not fade. Pencils work very well on plastic tags!

And don’t forget to start a garden notebook! Keeping records from year to year is both fun and very helpful. You will be glad you did when you go to order seeds next year, because it helps you to remember which plants grew best in your garden and which did not.


At the bottom of this resource, you will find information on how and when to start growing many common vegetable plants in Salt Lake County. Most seed packets will also let you know when the seeds can be started. For example, you would see the words: “Start inside 6-8 weeks before last frost.” In that case, just look at the expected last frost date – April 26 for Salt Lake County, and subtract 6-8 weeks from that date. You could start planting these seeds in the first few weeks of March. You will notice that on some plants, peas for example, there is no recommendation for starting them indoors. That is because peas are a crop that should be started directly in the garden, as they do not do as well when transplanted. Most cool-season crops should be sown directly outdoors, including all the root crops like radishes, beets, carrots and turnips.

Sowing the Seeds

First, prior to sowing, some seeds require that they are soaked first. Also, some large, hard seeds such as moonflowers do best if the seed coat is lightly chipped by using a nail file prior to soaking. This allows water to penetrate this hard outer barrier, called the “seed coat.”

Then, moisten your planting mix. Then fill your flats almost to the top with the mix, leaving a little bit of room at the top in each one for when you water. Next, drop seeds onto the surface of the planting mix. Small seeds such as petunias do not need to be covered – in fact, they need light to germinate. Other seeds can be covered with the planting mix to a depth about three times the thickness of the seed. You can very gently press the soil down, but don’t “smoosh” it. Plants need both water and air from the soil and if it is compacted too much, their roots cannot breathe and they will not grow well.

As you go along, label your trays. You can use popsicle sticks or plastic labels for this purpose, but it's also helpful if you draw a “map” of the tray, and label the map as you go. This way, if you drop or knock off a label, you’ll still know what that tray contains. Each tray can be labeled on the outside as well with permanent marker on a piece of duct tape.

Once you have seeded your trays, water the seeds in well. Using the plastic cup with holes poked in the bottom is an excellent way to do this without washing the seeds out and all over the place. Be gentle but generous with the water, as it helps create good contact between the seeds and the soil.

This is very important: Never let your seeds, or seedlings, sit in a tray of standing water for more than an hour or so. Make sure that if your tray does not have any drainage holes (which will be the case if you are growing seedlings indoors) that you take the flats of seedlings out, drain the water, and then put them back in. If you let them sit with “wet feet” they will rot.

Seeds need moisture and warmth to sprout. Some seeds, for warm-weather crops such as peppers, will not sprout in cold soil. You can use special heating pads designed for starting seedlings to keep them warm, but I just try to put them in the warmest area of the house. (Do not use an ordinary heating pad for this purpose, as it gets too hot and is not waterproof, so it's a fire/shock hazard!)

While you wait for your seeds to sprout, be careful not to let them dry out completely. If you have a clear plastic cover for the tray, you can use it while you wait for the seedlings to sprout. However, once they come up, I recommend that you remove it. Leaving it on may keep the plants too warm and moist, and they may “damp off.” Damping off is when the seedlings start to rot right at the base and fall over. To prevent this problem, provide good air circulation. If needed, you can use a fan in the room, but do not aim it directly at the plants.


Check your seedlings once a day if possible, but don’t water excessively. Only water once the soil begins to dry out, but don’t let it dry out completely. The color of the soil can be deceptive, so don’t use that as an indicator of whether you need to water. Instead, lift the pots up in the air. If they feel heavy, they probably are quite moist. If they seem very light, you will need to water. If you’re not sure, stick your finger down into the soil and feel the moisture level. You will find that as your plants get larger and more pot-bound, or if they are sitting in a very warm or sunny spot, they will need to be watered more often.

If you find that your plants look wilted, check to see if the soil is dry. If it is, immediately water them well, and let the water sit in the tray for an hour. Then take the seedlings out of the tray, pour off the water, and let them drain thoroughly before putting them back. If you find that your seedlings are wilted, but the soil is very wet (it may also smell bad), then they most likely have a bacterial disease due to overwatering. You will need to keep these away from other plants to avoid spreading this disease, and it is best to discard them. Do not reuse the soil, and wash the containers thoroughly.

Thinning Out

After the seedlings have all emerged, remove all but one seedling in each cell of the cell pack. Do this by cutting them with scissors, as it doesn’t disturb the soil as much. Note: the stems of seedlings are very easy to damage, so avoid touching them as much as possible.


Keep your seedlings away from radiators and other household heating devices, as these can dry them out or burn them very quickly. Each plant is different, so refer to the seed packet or your gardening reference books for the ideal growing temperature for that crop.


Bed Prep for inground beds (native soil):

Add nitrogen every year. Blood meal (12-0-0) is relatively affordable and easy to find. Use 2.5 lbs blood meal for every 100 square feet of garden space, working it into the top 6-8" of soil. Do not apply any bone meal (usually 4-12-0, 3-15-0 - very high in phorphorus) or kelp meal (potassium source) unless a soil report tells you to add those nutrients; Utah soil is naturally overabundant in phosphorus and potassium.

Supplemental Fertilization:

*Indoors: You may begin to fertilize your indoor seedlings as soon as they get their second set of leaves, called “true leaves.” Water with a half-strength solution of liquid fish/seaweed fertilizer every week or two. When in doubt, use less fertilizer than you think you need.


If you added nitrogen before planting, you should be fine, but it can be helpful to feed supplementally every two weeks with dilute fish emulsion until end of June.


If your seedlings are becoming too big for the cell packs, you can transplant them to larger, 3” pots. Instead of pulling up on the seedling, instead use your fingers to gently squeeze and press the bottom of the cell pack to loosen the soil. The seedling should come right out. Remember, seedlings are very delicate. Try to handle them by holding the root ball in your hand. If you need to, it is better to grasp them by their leaves than the stem, as the stem is easily damaged.

Always plant your seedling in the new pot at about the same level that it was growing in the cell pack. If you bury the stem more deeply than it was growing before, then the plant would have to grow a whole new root system. If you leave the root ball sticking up out of the soil, then the plant will dry out.

Note: Wash Your Hands!

If you smoke, make sure to wash your hands before handling your seedlings, especially tomatoes and peppers. Tobacco mosaic virus, a plant disease, can be carried by cigarettes and spread by touching the leaves of susceptible plants.

Planting Information for Salt Lake County - Vegetables

  • Beets - Sow directly in the garden in late March/early April and again in late July. Presoak seeds for 1-2 hours and ensure good contact with soil for best results. Plant in succession for a long harvest.
  • Beans - Direct sow in mid May or once soil temp is over 65 degrees. Presoak seeds 1-2 hours. Using inoculant at time of planting may be helpful.
  • Carrots - Direct sow in late March/early April. Germination is very slow, plant in succession.
  • Corn - Direct sow in late April or May once the nights are above 50°. Plant in blocks (at least 4' by 4'), not a single long row, for good pollination; keep sweet corn away from ornamental corn to prevent cross-pollination (flavor will not be as good).
  • Cucumber - Plant in individual pots in late March, keep warm for good germination. Germination is aided by warmth. Plant out after danger of frost has passed. May do better directed seeded out into the garden. Consider growing these vertically up a trellis.
  • Garlic - This is best grown from "seed cloves," small cloves that are ready to be planted in the fall (mid-late October).
  • Kale - Start kale in early spring in a cold frame or indoors for an early harvest. Does best in cold weather.
  • Lettuce - Indoors in late February or March (or it can be started earlier if you can cover it from heavy frosts outdoors). Plant transplants out in late March/early April, when the plants are about a month old. Also easy to direct seed out in the garden in March. Does not do well once the weather gets too hot; plant again late in July or August for fall harvest.
  • New Zealand Spinach - Start indoors in late March or direct seed in early May. Presoak overnight. Plant out after danger of frost has passed. (Spinach-substitute that does well in warm weather.)
  • Onions - Indoors in January or February, outdoors in late April or early May. Plant outside at the end of April. Try to keep weeds out as much as possible for best results.
  • Orach - Direct sow in mid-April. This is a drought tolerant green that still tastes good once it "bolts" (which means to grow a flower stalk)
  • Peas - Plant directly in the garden in succession from late February up to early April; Wando is a good short season variety for late plantings. Using inoculant at the time of planting may be helpful for best growth. Know if your pea variety has a bush (self-supporting) or climbing habit.
  • Peppers - Plant indoors in March. Germination is aided by warmth. Plant out during the 2nd week of May. When you plant out, use a collar around the stem at ground level (can be made from an index card) to protect from cutworms.
  • Pumpkin - Indoors in 3" individual pots in mid-April or plant outdoors early May. Pumpkins, squashes and other vines need lots of room in the garden. Plant outside after the danger of frost has passed. Does well planted with corn, as in a traditional "Three Sisters Garden" with beans, corn and squash.
  • Radishes - Plant outdoors as soon as soil can be worked. Plant in succession all during the spring, start planting again in late July/early August for fall harvest. Very easy to grow and fun for kids!
  • Summer Squash - Plant outdoors mid May. Summer squashes have a sprawling bush habit and need lots of room in the garden. This type includes zucchini, patty pan and yellow crookneck squashes.
  • Winter Squash - Plant outdoors in May, once soil is warm. Pumpkins and winter squashes need lots of room in the garden. Winter squashes include acorn, buttercup, butternut, and Hubbard. Most winter squashes will easily climb a trellis (vertical gardening) to save room in your garden.
  • Tomato - Plant indoors in late March. Germination is aided by warmth, then grow on at cooler temperatures (60 degrees is good). Plant outside after ALL danger of frost has passed.
  • Watermelon - Start indoors in individual pots in mid April or plant outdoors after the danger of frost has passed. Watermelons also need lots of room to grow, seeds need warmth to germinate. Plant out once danger of frost has passed, and once the second pair, called "true leaves" emerge.