Starting Your Summer Vegetable Garden—Seeds or Transplants?
This article is written to inform the casual or beginning vegetable gardener who faces many choices when starting plants. Below are recommendations for the best way to plant some of the more popular garden vegetables.
This article also assumes that you will be purchasing transplants. Please be aware that growing your own transplants through starting seeds indoors requires understanding the process as well as providing the right environment for the seeds to germinate and grow. In almost every case, seeds started indoors will require heat to germinate and artificial light to grow. Please review the resources listed at the bottom of this article for further information.
Best to Direct Seed
You should have good luck starting the following edibles from seed sown directly into the garden. In some cases, you will not even be able to locate transplants. They are listed in the order that they can be sown in spring.
Peas – In much of Pennsylvania, folklore holds that peas should be sown on St. Patrick's Day. Peas will germinate as long as the soil is above 40°F. These vegetables grow best in cool temperatures, about 55° to 65°F. In fact, peas will stop setting blossoms (which turn into edible peas) when the temperature is above 85°F, so plant peas 50 to 70 days before hot summer temperatures arrive.
Spinach – Spinach seeds should be planted outdoors in April since this vegetable needs to be harvested before it bolts (goes to seed) in the summer heat.
Leaf lettuce – Leaf lettuce can be sown beginning in April, and you can continue to sow a succession, based on variety, until around August 1.
Root vegetables (beets, carrots, parsnips, radishes, rutabagas, and turnips) – Transplanting these types of vegetables may cause misshapen roots. Since this is the part of the plant you want to harvest, direct seeding is much better than transplanting. Beets may be an exception if you transplant them carefully into very loose soil. Most of these root vegetables can be planted in April, but check the seed packet for exact instructions.
Beans – Snap beans seeds should be planted when danger of frost has passed. Bush beans can be sown at two-week intervals for a continuous harvest.
Corn – Corn seeds may be planted between May 1 and July 1. If you have enough room, you can plant corn at intervals for a staggered harvest. Keep in mind that the corn that is planted later will mature in less time. Corn thrives in heat.
Best to Start from Transplants
Early cabbage – Plant transplants from mid-April to late May.
Early broccoli and cauliflower – Plant in early April.
Head Lettuce – Head lettuce and romaine transplants should be planted outdoors as soon as the danger of a heavy frost has passed.
Eggplant, peppers, and tomatoes – These related plants should be transplanted into the garden when the soil is warm. An indicator is when air temperature is about 60°F at night and 70°F during the day, late May to early June in much of Pennsylvania.
Direct Seeds and/or Transplant—Special Considerations
Cucumbers, Melons, and Squash – Grouped under the term "cucurbits," these plants can all be direct seeded in the garden after the danger of frost has passed. But depending on the length of your growing season, you might achieve a greater harvest from transplants started indoors 3 to 4 weeks in advance.
Onions – You will often find onions starts offered as "sets," which are small bulbs. Plant these in early to late April. Green, or bunching, onions are often found as transplants at garden centers. Onions can be direct seeded, but I recommend sets or transplants for a novice gardener.
Potatoes (white or Irish)– Potatoes are started from seed potatoes. They should be cut into pieces that each contain an eye and planted in early spring. They can weather a light frost.
Fall Planting
In many cases, plants that are best started as transplants in spring can be direct seeded in the summer for a fall harvest. These include cabbage, broccoli, cauliflower, onions, potatoes, spinach, squash, and root vegetables.
Seed Sowing Tips
Let the seed packet be your guide regarding the depth and spacing when sowing seeds. Generally, seeds should be planted twice as deep as they are wide. Cover the seeds with compost or vermiculite if your garden soil is particularly clay-like. Keep in mind that rabbits love young, tender growth, so consider a chicken wire barrier to protect the sprouts until they become more mature and less appetizing.
Transplanting Tips
Check to see if the transplants have been hardened off before planting outdoors. Hardening off is a process of gradual exposure to outdoor conditions that toughens the plant. If they have not undergone this process, place them in a protected outdoor area for an increased amount of time every day for at least a week. Pick a day that is not extremely sunny or windy to transplant them in the garden. Plant them slightly deeper than they were in the container. Tomatoes can be planted even deeper, leaving two or three sets of leaves exposed. Water the soil around the base of the plant immediately after transplanting and continue to make sure the transplants stay well-watered.
For More Information
There are many more vegetable choices than described in this article and a wealth of variety within common vegetable types. Therefore, be sure to consult seed catalogs, seed packets, and your local garden center for exact growing instructions. The Master Gardeners in your county can also offer research-based advice; contact them via their Garden Hotlines. Finally, Penn State Extension offers an excellent, inexpensive resource: Vegetable Gardening: Recommendations for Home Gardeners in Pennsylvania.
The following articles provide a wealth of information for the novice vegetable gardener:
