Time to plan your summer vegetable garden!

Spring is finally upon us here in New Hampshire, so it’s time to think about growing summer vegetables. In class, we started seeds for transplant into our high tunnels a couple of weeks ago. But don’t worry, you still have plenty of time to start seedlings of your own for spring transplant and summer harvest! In this post, I’ll break down the steps to take now for planning a summer vegetable garden from seed.

Image: theguardian.co.uk

Firstly, you’ll need to know how much space you have to deal with. Draw your garden plot to scale (graph paper might help). If you have a large garden (greater than about 4 feet in either dimension), mark out rows 3-4 feet wide with walking paths of about 2 feet between them. Also consider the amount of time you will have to maintain your seedlings and your outdoor garden. Given the space and time you have, decide how many different crops you want to raise, and what they should be. Note that the fewer different crops you choose, the easier they will be to manage.

Look through a seed catalog, or a seed-supply website, to choose varieties for each of your crops. We get our seeds for Farm to YoU NH from Johnny’s Selected Seeds, an employee-owned company in Maine. If you are aware of pest or disease problems on or near your land, be sure to choose varieties that are resistant to those problems, if they are available. If this is the first vegetable garden on your plot, consider how wet the area is. If it doesn’t drain well, your plants will likely be at higher risk for fungal disease, so try to choose disease-resistant varieties.

Image: thedemogarden.org/garden-templates/

Block out your garden diagram with the varieties you’ve chosen, keeping in mind your desired harvest of each crop and the relative sizes of the mature plants. (For example, tomatoes take up a lot more space than carrots.) Proper air circulation and light availability are very important, so be sure not to overcrowd your garden. In NH, sunlight comes from the south, so place shorter plants to the south and taller plants to the north to avoid shading out the short plants.

Once you have a layout planned, you can figure out how many plants of each variety you will need. You can either use the spacing information provided in your seed catalog (or on the seed packet itself), or use an online tool like this one from Johnny’s. Plan to start 10-20% more plants than you will actually need, in case some don’t germinate.

Next, use a calendar to plan planting and transplant dates. In NH, most growers wait until Memorial Day weekend to plant outside, to avoid the possibility of a late frost. Using this date as a guide, mark on your calendar your desired transplant date. Then count backward from that date to find your seed-planting date(s). Refer to the table below for the number of weeks from seed to transplant in the field, or use the Johnny’s calculator, which gives dates for many different crops in one table after you enter the date of last frost.

Image: New England Vegetable Management Guide, 2014-2015 Edition.

Now you’re ready to buy or order your seeds. But don’t forget the media and containers! For seedlings, a finely-textured potting mix is ideal. Many mixes are marketed specifically for seed-starting. There are several different styles of containers for starting seeds, and which type you should choose depends largely on personal preference.

There are two things, however, that all of your seeds will need to be successful: moisture and heat. Make sure your potting media is thoroughly saturated before planting, then follow the directions on each seed packet for seed spacing and depth. Different seeds need different temperatures to germinate, so you might need a heating pad (available at garden centers and seed suppliers), depending on your crop choices and the temperature in your propagation area. Use the chart above to determine optimal temperatures for your seeds. Notice that after germination, most seedlings require lower temperatures for optimal growth, so adjust or remove any supplemental heat once the seedlings have emerged. Don't forget to label your containers; most seedlings look very similar to each other!

To take care of your planted seeds once they are in a warm environment, keep the potting media moist, but not constantly saturated. Too much water can be just as detrimental to the growth of a seedling as too little water, and can lead to problems like root rot. For the first few days of a seedling’s life, it draws on stored nutrients from the seed, so fertilizer is not required. Some seeds, like lettuce, do require light for germination and need to be planted close to the soil surface. Once the cotyledons (the first, “false” pair of leaves) have emerged from the soil, the plants will begin photosynthesis, and should be kept in a well-lit area to grow into strong transplants.