What to do when your seedlings grow too big

I started my peppers too early.

Every year I warn fellow gardeners not to rush on getting seeds into pots for warm-weather vegetables. Tomatoes, in particular, outgrow their indoor space under lights much faster than you’d think, but you can make this mistake with many plants that shouldn’t go outdoors until the chance of frost is past and the soil temperature is at least 60 degrees F. There’s often a several-week gap between the average-last-frost day that you used to count back from when calculating start dates and the actual day that it’s safe to put the plants in the garden. That can go either way, of course, but unless you’re inclined toward taking risks, it’s better to err on the side of later planting. The seedlings will grow faster under warm conditions and catch up with their early-planted peers.

So, there was no reason to put the pepper seeds in as early as the very end of February, but I did it anyway. We all have those moments. Mid-March would have been fine, but I know I was feeling anxious about other things and probably projected those feelings onto my peppers. And now I have some large strong well-grown pepper plants that are more than ready to go into the ground–which some of them are going to do this week, soil temperatures notwithstanding.

Some of my large pepper plants hardening off, guarded from inside by a helpful cat

If you have been in this situation, which most of us seed-starters have, here are some things you can do, more or less in chronological order. This applies also to plants you may have bought a while before you could plant them–we all do that too!

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Soil temperature and why it matters

soil thermometer in the ground
Soil thermometer. Photo: A. Bodkins

Sunshine, increasing temperatures, warm rain showers, and the return of migratory birds are all signs that Spring is getting closer. They are all reasons to be excited about Spring and all the possibilities that the new gardening season will hold.  

It’s always tempting to go out and start sowing seeds at the first glimpse of sunshine, but most seasoned gardeners know that patience is the best policy. It takes several weeks of warm air temperatures and sunshine for the soil temperature to get warm enough to signal the seeds to germinate. Mother nature provides mechanisms to protect seeds from germinating too early (called “seed dormancy”) and there are certain requirements that must be met before sprouting occurs. 

Did you know that every seed has an optimum range of soil temperatures for germination? This factor helps determine which seeds are cool-season versus warm-season. Penn State Extension has a great article regarding Soil Temperature and Seed Germination that you should spend a few minutes reading. 

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Seed starting and soil testing: a Master Gardener outlines his spring gardening progress

In mid-February, I started my Gypsy, Monty, and Green Magic broccoli, Snow Crown cauliflower, Lacinato kale, several types of lettuce, and some Big Blue salvia.

Italian flat-leaf parsley was started in mid-January. Most of these transplants will be planted in the garden or containers in the first week of April after hardening off for at least a week in my cold frame. My pre-sprouted snap peas will be planted in late March. Planting dates for central Maryland can be found here on the Home and Garden Information Center website.

Kent's seedlings

In early March, I will be making a trip into Baltimore to get some other seeds for Sugar Ann snap peas, Jade string beans, and a couple of other things. In late March, I will be planting some seed potatoes in containers, just to see what the yield is. On March 27th, seven to eight weeks before the spring plant out date of mid-May, I will be planting Galine eggplant and several different types of peppers.

In previous years, I’ve planted tomatoes six weeks prior to my plant out date, but they have been leggy. This year, I’m planting them on April 10 for planting in the garden and containers on May 15.

My latest soil test, done in May of 2019, says to incorporate one pound of nitrogen (N) per 1,000 square feet. Only N is required since the beds contain the optimum amount of phosphorus (P) and potassium (K) and are at the correct pH.

To determine what fertilizer needs to be added to my beds which are 32 or 40 square feet, I will have to convert this recommendation to determine the amount of urea (46-0-0) to apply to my beds. This is fairly simple to do, using the following equation. Amount of N/.46 (% of N in urea) x beds size/1000 square feet. This yields the following: 2.17 pounds of urea x 0.032 for a 32 square foot bed equals .069 pounds of urea or 1.1 ounces. I guess I’ll have to get out my kitchen scale.

Alternatively, the University of Delaware suggested 2.5 pounds per 1000 square feet or 2.5 x .032 = 1.28 ounces of urea. This calculation works for almost all recommendations from soil test labs. However, if in doubt, you can always Ask a Gardening Expert at HGIC.

By Kent Phillips, University of Maryland Extension, Howard County Master Gardener

What can you start from seed in February?

I hope all of you are busy planning your vegetable gardens and getting those seeds ordered! If you haven’t purchased seeds yet, now is the time. A lot of seed companies are experiencing larger than usual interest and several have had to temporarily stop accepting orders. Many varieties of seeds are running out. So jump on it!

If you already have your seeds and your plan of action, you may be champing at the bit to get started. Those of us who start seeds indoors feel the urge to play in the dirt (or the soilless seed-starting mix) even in winter, but it’s often not a good idea. When I began gardening, I started many plants far too early, and was sorry later when I had enormous seedlings that couldn’t be put in the ground until the weather cooperated. So as a former offender, I will state clearly: DO NOT START YOUR TOMATO PLANTS IN FEBRUARY. In fact, do not start your tomato plants until late March or early April, and you will be much happier, and so will your plants.

But what CAN I start, you ask, with a pitiful, yearning look in your eyes. I know. I really do. Here’s a  list. It may not include anything you’re actually planning to grow, but I’ll give you another suggestion at the end. Here we go.

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Time to think about fall planting!

Wait… what?

It seems like you’ve just put that spring vegetable garden in… though actually, come to think of it, there are tomatoes reddening and squash burgeoning and summer is in full swing. But still, fall seems a long time away. Can’t we wait to think about it until it gets chilly again?

Well, if all you want to grow in the fall are lettuce and radishes, and maybe some spinach, sure. Given our tendency to long, warm autumns, you may be enjoying your summer vegetables well into October, or even November, if we don’t get a hard frost, so who needs to plant anything else? But those long autumns also mean we have an ideal situation for keeping our production going into winter. And if you planted broccoli or cabbage or cilantro this spring, or any other plant that prefers cool weather, and were disappointed when it went to flower early or began to taste bitter, let me tell you: fall is better. Temperatures that start a little warmer for tender seedlings and grow gradually cooler, resulting in frost-kissed sweetness and beautiful greens or root vegetables–terrific! You just need to do a little work to get there.

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