How to Craft a Spring Seed Starting Calendar

by Ken Greene

Squash Seedling

From the soft comfort of a fireside rocking chair, your garden holds endless possibilities. You can picture, taste even, the sweet tang of your certain bushels of Blush Cherry Tomatoes, the crisp crunch of Silver Slicer Cucumbers, the melting delicateness of a pile of stir-fried Swiss Giant Snow Peas. All of this dreaming is essential, and at least partly true, but luckily January moves along, and wispy garden dreams must solidify into concrete garden plans if you hope to bring your visions to life.

Although your seed order may come in all at once, it's important not to start your seeds all at the same time, no matter how impatient you're feeling for spring! There are many garden plans to be made - questions of fencing, fertility, and size among countless others - but one of the most vital tasks is planning your spring schedule for starting seeds.

Note: This post is about spring sowing and vegetables. We'll follow up with future articles on succession sowing (yes! you can keep planting all season long) and starting flowers from seed.

Some seeds need to germinate in cool weather, while others sprout in warm conditions. At the same time, some varieties mature to harvest stage rapidly while others can take a long season to fully ripen. You want to make sure there are enough days from germination for plants to flower or fruit before the season is over!

The key information to know when the time is right is your last spring frost date. (If you live somewhere with no frost and a long growing season we're green with envy!)  This date is the average last day that gardeners can expect a frost to visit their garden. (And isn't it fun to think about the last frost date? It will happen!) Key word here is average. For example, here in the Mid-Hudson Valley, this date is about May 12th. However, this date differs significantly throughout the state  and it is also often refuted by actual fact. In 2012, for example, much of the Hudson Valley experienced a late May frost strong enough to damage frost-tender crops significantly. So keep your row cover handy! Still, we need a starting point, and the last frost date is it.

Brassica Seedlings

Below is a schedule of spring seed-starting windows. You can use this as a guide and change it up based on where you live.

Make Your Own Seed Starting Calendar

1. Look up your "last frost date" here. (See instructions below for how to interpret the graph.)

2. Mark it on a calendar (and what better than our Art of Seed Garden Calendar).

3. Use the info on the chart below to count back the correct number of weeks for a given crop family and mark that date range (or draw a little picture of a tomato, cuke, broccoli, pepper, melon etc. if you're so inspired.)

That should keep you on track for successful seed starting and timely harvests.

Last Frost Date Chart Instructions: Click here for chart.

Once you've selected your state the chart pops up. Scroll down to find the weather station closest to you. There are a lot of numbers on this chart you can ignore! Use the "Threshold" line marked "32". Follow it across and use either the 50% column of 10% column. These are the dates when there is a 50% or less chance of frost and 10% or less chance of frost. All depends on how much you want to gamble! (We use the 10% while keeping an eye on actual weather.)  This chart also gives you your first fall frost date range. A bonus is the "Freeze Free Period". This is your "growing season" - or the number of days you have for plants to fully mature from transplant/direct sow to first killing frost.

So, in the highlighted example below, if you lived near Addison, NY there's a 50% probability of a 32 degree freeze on May 18th and September 30th. There's a 10% probability of a 32 degree frost on June 4th. This creates (roughly) a 113-135 day growing season.

Seed Starting Schedule:

There are three date windows below for different ways you'll be starting seeds.

Chart #1. "Indoors" means in a cold frame, greenhouse, or indoors with supplemental lighting.

Chart #2. “Transplant” refers to seeds you started early under protection, harden off by slowly exposing them to the outside elements, and then transplant into your garden.

Chart #3. “Direct Sow” means seeds you plant directly in the soil outside.

Spring Seed Starting Schedule (click here for a printable version)