Starting Seeds Indoors

Summer is still a dream, I know, but I sure am glad to be starting up my column again and, at least, beginning to think about gardening. Last year, about this same time, I devoted half of my column to starting seeds and I got so many questions from readers on how to tackle specific things, I’ve decided to write on the subject again. This time, though, I’ll go into more detail. (Of course, you’re still welcome to e-mail questions if something seems confusing, or you want to know more.)

If you’re looking to save some money on plants, growing at least a few from seed is the way to go. While perennials can sometimes be a little finicky, annuals are usually easy to grow — even if you’ve never started seeds before. One thing I really appreciate about growing my own plants is that it allows me to have some things in my garden that I just can’t find in stores, such as love-lies-bleeding (Amaranthus caudatus), sea holly (Eryngium spp.) and Chinese lanterns (Physalis alkekengi). 



The first thing most everyone wants to know when considering starting seeds is what to buy. There are a lot of fancy seed-starting apparatus out there and I’m here to tell you that you don’t need the bulk of them. I start seeds in my basement every year on a set of cheap metal shelves I got at Menards. I don’t buy pricey grow lights. I use cool fluorescent shop lights that hang above each shelf on chains. The chains allow me to adjust the height of the lights as the seedlings grow (more on this later).

People use all sorts of containers for starting seeds: milk jugs, egg cartons, plastic trays and flats. It’s really a matter of personal preference, I say. And you’ll learn what works for you once you try this a couple of times. I once used those little round peat discs you see sold in packages of 30 or more in stores — they look kind of like burlap poker chips.

Once you wet the discs, they expand into neat little bundles that you can plant your seeds in. The only trouble with them, as I see it, is that they dry out quickly. So you really have to be diligent to keep them well watered.

I like to plant my seeds in 12-ounce, clear plastic cups. I have to fill these with more growing medium than I would have to use in a smaller container. But the payoff is I don’t have to transplant the seedlings into larger, individual containers once they really start to take off. I just thin them out in their cups, leaving only one or two plants in each.

To start seeds, you want a growing medium that is light (to give seeds air), porous (to allow proper drainage) and sterile (to preclude disease). You can buy soilless seed mixes or you can make your own using equal parts peat moss, fine perlite and vermiculite.

Seeds usually germinate best when the soil is warm and moist. Because seedlings don’t need light to germinate, you can put them on top of your refrigerator or other warm spot. (Windowsills aren’t a good choice, usually, because they can be drafty this time of year.) Or you can purchase heating mats or cables to place under your plants in your prepared growing area.

Directions on the back of your seed packets will usually tell you what you need to know, including how deeply seeds should be planted, how long until germination and whether the seeds need to be treated in any way before planting. These treatments, such as soaking seeds in water, scuffing the seed coat or placing them in a cold environment for several weeks before sowing, are often integral to a successful germination process. If there is no recommendation for planting depth, the general rule is to plant seeds twice as deep as the seed’s size. Small seeds, such as poppy seeds, should be thinly scattered on top of the soil and very lightly covered. (Germination tips on a wide range of species can be found at 
www.backyardgardener.com.)

While many seeds need to be planted just four to six weeks before being moved outdoors, others that are slower to mature (such as begonias, geraniums and pansies) need to be started 10–12 weeks before being transplanted. Timing is important because you want your seedlings to be strong enough to manage on their own, but you don’t want them getting so big that they crowd each other and compete for light, water and nutrients.

Moisten your potting mix before starting to plant. As you sow your seeds, be sure to label each container or you’ll just forget what you’ve planted and wind up having no idea what you’re putting into your garden come spring. (I speak from experience here.) Once everything is planted, lightly mist the top of the soil with warm water and cover each container with plastic wrap to help keep the seedbed humid and moist. Continue to mist plants, or water very gently, as needed.

Once your plants have emerged from the soil, you can remove the plastic wrap (or plastic cover if you’re using the trays). I like to leave my seedlings covered, though, because it keeps them from drying out so fast. I cover my cups with plastic wrap, leaving the sides open so air can get in. As plants grow, I use toothpicks or tongue depressors to keep the plastic away from the seedlings. Heating units should also be turned off at this point. And now it’s time to switch on your lights, keeping them about 4 inches above plants, so raise your lights as your plants grow. Keep your lights on at least 14 to 16 hours each day. I find it’s easiest to just put them on a timer.

Check seedlings regularly so they don’t dry out. Once they get their first few leaves (their “true” leaves, not the first leaves they get, known as “seed leaves”), feed them with a water-soluble fertilizer mixed at quarter strength once a week. I like to use fish emulsion, though it is quite smelly. Soon the dreaded time of thinning will come. (I dread it, anyway.) Though it feels like killing your darlings, you must thin the crowd in each seed container, leaving only one plant, maybe two, in some cases.

After the threat of frost has passed, usually around Mother’s Day (May 10), your seedlings will be ready to transplant into the garden. But first, it’s best to help them get accustomed to outdoor conditions by helping them “harden off.” To do this, you’ll be taking the plants outside to a sheltered spot daily, a little longer each day. After a week or two, they’ll be ready to move to their new homes and you can take a few minutes to write down what worked and what didn’t so you’ll be ready for next year.

This post originally appeared in the Southwest Journal.