Be strategic when you nurture those seedlings

Meet Mike!

Mike will appear at the Fredericksburg Spring Home Show on Saturday and Sunday, March 18–19, at the Fredericksburg Expo Center in Fredericksburg, Virginia. Mike will speak at noon and 3 p.m. on March 18 and at noon and 2 p.m. on March 19. Find out more on the show’s website.

“Leggy” not a good look for seedlings

Bob, from the Hagerstown, Maryland, area, writes: “Some of the plants I’ve been starting from seed are getting tall and leggy. I’m about to restart some varieties for the third time due to this problem.”

Well, first, it sounds like you’re starting your seeds way too early, Bob. Forget trying to time things by your area’s published “last average frost date”; tropical plants like tomatoes and peppers should not go outside until nighttime temps are reliably in the upper 40s and 50s. That’s generally around May 15 or later in these parts.

(But don’t go by the calendar. Check the long-range forecast before you take your baby plants outside, and keep them indoors a bit longer if nights are expected to drop anywhere near or below 40 degrees.)

Set up your timing like this: You want the plants to be about six weeks of age when they go outside. So consider May 15 as a decent out-of-the-house date, add a week up front for the actual germination of the seed, and you’re talking about a reasonable seed-starting date of March 20 or so.

Heating mats are only for germination, not growing

Bob continues: “I put the seeds in containers and give them a bit of water. Then the trays of seeds go underneath lights on a grow rack. I also have heating mats under the trays.”

There’s a couple of rookie mistakes you might be making here, Bob. Seeds that have not yet germinated don’t need light. (They’re underground!)

Heating mats are great for providing the exact amount of bottom heat that gets seeds germinated quickly. But after the seeds are up and sprouted, the mats should be turned off, or they’ll keep the soil too warm and weaken the plants. (The seeds need warm soil to sprout. But after that, the plants flourish with an indoor air temperature in the 60s.)

Once your seeds have sprouted, the thing that young plants want most is bright light and lots of it, and that’s where most seed-starters fail.

Lights, lights & more lights!

Bob is trying to start his own plants from seed, but they’re coming up tall and leggy. That’s because young plants need much brighter light than most people suspect, Bob. The worst kind of light comes from a so-called “sunny windowsill”; it probably isn’t all that sunny, but it probably does get too cold at night.

Four-foot-long fluorescent tubes (as in a basic shop light fixture), are great for baby plants, but most people don’t keep the plants close enough to the lights. Use hanging chains to adjust the height of the fixture upwards, or place books underneath the plants that you can remove as the plants get taller, but be aware that your goal is to always keep the tips of your baby plants within an inch of the tubes. That’s right: an inch — the light intensity (lumens) of florescent lighting drops off dramatically after even a short distance. And fluorescent light is cool, so the plants won’t get cooked from being so close.

(Oh, and while a two-tube shop light is great, a four-tube fixture will give you garden-center quality plants!)

Seed starting 101

• Fill the same kind of small plastic containers that garden centers use (no old egg cartons!) with a light, loose, bagged seed-starting mix (aka “soil free mix,” “professional mix” or “potting mix”).
• Do not use garden soil, and avoid bagged soils that contain chemical fertilizer or those creepy water-holding crystals. You may have to search a bit for a clean seed-starting mixture, but independent garden centers should carry a nice selection. (If they don’t, yell at them. Use my name.)
• Sit the filled containers in a sink of water until they’re heavy and saturated.
• Place two seeds in each container.
• Cover the seeds with a little bit more mix.
• Cover the containers with clear plastic wrap and put them on a heating mat or just a warm table in your home.
• If a few days pass and no water drops are apparent on the inside of the plastic, lift it up, mist the surface with plain water, and then recover the containers.
• When the very first sprouts appear, immediately remove the wrap. (The remaining plants will pop up over the next day or two.)
• Turn off any extra heat and get the baby plants under bright lights; an inch away from brand new 4-foot-long fluorescent tubes is ideal. Run the lights for 16 hours a day.
• Gently feed the plants with compost tea or worm castings when they’re around four weeks of age.
• If more than one plant has sprouted in any of the cells, use small scissors to cut the tallest, or weakest-looking one off at the soil line at the three- or four-week mark. Don’t yank it out or let it continue grow; it will diminish the health of the good plant.

Be warned: Seed starting is harder than gardening

And finally, don’t despair if your seed-starting attempts yield poor results the first year or two; nobody gets seed starting right off the bat. It is much harder to raise little plants from seed indoors than to nurture big plants outdoors; the skill set is totally different.

And the only way to get really good at it is to try and fail a couple of times.

Do your best to follow the detailed instructions above. But be prepared to buy replacement plants without shame in the spring. You don’t want to start the season with weak sickly plants; you’ll do much better the following year.