Growing Great Transplants

Any gardeners are content to buy transplants for their garden each season. It is a fast, easy way to get started whenever gardening fever hits. However there are some great reasons to grow your own transplants and sooner or later most serious gardeners will try their hand at producing transplants themselves.

One reason to grow your own transplants is to expand your choice of varieties. Garden centers usually carry only a few varieties of a given species and those are most often older varieties familiar to the masses. If you have a special old favorite or perhaps wish to try something new you will likely need to grow it yourself.

Another reason to raise your own transplants is timing. If you want a head start, or if you are planting in a season when supplies are typically unavailable, such as July planted tomatoes for a fall garden, you’ll do best to grow your own.

A final reason is transplant quality. Unless you are fortunate enough to have a great full service garden center nearby you may have noticed that transplants can tend to be small at times and may be stressed from lack of care. In some chain stores, watering and caring for the latest shipment is apparently not a priority.

Keys to Success

If you have tried growing quality transplants with less than ideal results, here are a few key tips to get you off to a good start. It is really not difficult at all if you provide them the conditions they need, namely a quality growing mix, good lighting, proper temperatures and appropriate nutrition.

Mixes and Containers

Garden soil is fine for gardens but is not the best choice for raising transplants. Soil often contains disease organisms that may cause problems for germinating seeds.

Special artificial media for seed starting are typically very fine textured and are made from a mix of peat and vermiculite or perlite. Regular potting mixes although coarser in texture are also fine. Smaller seeds may fall in between the chunky pieces, which makes planting at the proper depth difficult and results in erratic germination. Whatever mix you choose, it should be free of diseases. I prefer to start with a fresh new mix each time to avoid such problems.

A good container for growing transplants is simply one that drains well and provides adequate room for roots to develop. The traditional six pack trays are a great choice, but if you are growing large numbers of transplants you may want to invest in a reusable tray. Plastic trays and Styrofoam trays both work great and come in various cell sizes. Then there are the peat pots and peat pellets which swell up when wet to form a container for growing transplants.

I have seen many other unique and inventive choices for growing transplants including egg cartons, milk cartons cut lengthwise, Styrofoam coffee cups, and homemade paper pots. Most anything will work if it has a hole for drainage. Just keep in mind that with larger containers it is easy to keep the soil too wet as the small developing plants lack much root area. Likewise, very small containers may require frequent watering and may result in stunted transplants if the growing plants are left too long before being moved up into a larger container.


You may want to sow seeds directly into smaller containers such as six packs, or sow them into a larger flat for transplanting later. If you sow into individual containers place two seeds per container to hedge your bet and plan on removing one later on if both germinate and grow. Pinch or snip the extra seedling off at the soil level rather than pulling it up to avoid damaging the remaining plant.

imagePlanting into an open flat saves space. You can later transplant a few of the better seedlings into individual cells to get the desired number of transplants, and simply discard the rest or share them with a fellow gardener.

It is important to plant seeds at the proper depth. As a general guide sow seeds at a depth of about 2 to 3 times their width. Some seeds need light to germinate and should be sown on the surface rather than buried. The seed packet includes the particular seed sowing instructions for each species.

Seeds need a moist environment in which to germinate and grow. It is best to moisten the growing mix before planting because dry media can tend to shed water, but once moistened they absorb moisture readily. Standard spray nozzles put out water in coarse drops and can blast mix or planted seeds away. It is better to purchase a fogger nozzle which puts out a fine mist and is ideal for wetting seeds.

You can also set the seed tray in a shallow container of water for a while to allow the moisture to “wick” up into the planting mix.

After planting, the seeds start to absorb moisture and a complex chemical reaction begins that leads to the emergence of a root and a shoot. If the germinating seed is allowed to dry out during this period it will die.

Keep the growing media moist by misting it regularly. You can purchase trays with plastic covers at most garden centers these days. As an alternative, I like to place the entire flat into a clear plastic bag to hold in moisture. Those large bags from a dry cleaners work great for this purpose. Another option is to lay a clear sheet of plastic over the soil surface. Check the flat often so you can remove the plastic bag or covering as soon as seeds begin to sprout and grow.

The seed leaves are the first to emerge. These are followed by the first true leaves. If you are transplanting newly emerged seedlings to growing containers this is the stage to do so. Take care to handle them by the seed leaves. If these are damaged there is no significant loss, but if you crush a stem or true leaf the seedling will be either set back or destroyed outright.


The process of germination is pretty automatic and, as long as the growing mix is disease free, the mix stays moist and temperatures are right, seeds are likely to germinate fine. With the exception of a few species, most plants will germinate without much light. However once the seeds break through the surface and take off growing the gardener needs to make sure lighting is very good or the transplants will suffer.

The best light is natural light. Seeds don’t necessarily need direct sun, but do need bright light. In dim lighting the seedlings will stretch and grow very spindly. I prefer to place the seed trays near a bright window in winter, or outdoors in a bright shady location in summer.

Window locations can lack adequate lighting and seedlings will tend to lean toward the light. Turn trays daily to keep them growing upright. I have devised an effective reflector that works quite well; even well enough to keep a cactus dish garden happy during the winter months.

Take a tri-fold foam core poster size display board and glue or tape aluminum foil or radiant barrier to one side. Place it around the seedling tray on the interior side to reflect outdoor light back into the seedlings. This setup increases total light levels significantly and can make an average window quite adequate for raising transplants.

When you don’t have a bright window, artificial lights can work quite well. We have come a long way when it comes to options for artificial lighting designed to grow plants indoors. If money is no object, home gardeners can purchase a variety of HID (High Intensity Discharge) light systems including metal halide and high pressure sodium lights that can even grow a tomato to successful production in a dark garage!

Most gardeners are not into such intense indoor gardening and simply want an economical way to get seedlings off to a good start. Thankfully an inexpensive florescent fixture can do the trick. I should note that standard light bulbs (incandescent bulbs) are inefficient, producing a significant amount of heat compared to the light produced. They tend to create a light near the red end of the spectrum and as such are not good as a light source for transplants. If you place them close enough to provide adequate illumination, the heat they give off will fry your plants!

Florescent lighting is much more efficient. Its light spectrum is more toward the middle of the spectrum. While it may not be sufficient for long term growth and production (remember that tomato in the garage?) it is adequate for starting seedlings. Florescent lights are best used to supplement marginal natural lighting, but in a pinch can suffice in a location without natural light.

There is a wide variety of special florescent tubes on the market. Some are sold as plant lights, others promise a warm sunny glow or go by names like Grolux and Vita Light. Their spectrum is better than standard florescent tubes but may not be worth the cost. Compared to standard tubes these specialty lights are much more expensive. Research at Cornell and North Carolina State indicated that these lights are not necessary for growing short term transplants. The researchers also found that to alternate a standard cool white tube with a warm white tube worked better than one type of tube used alone.

I like to use standard 4 foot shop light fixtures with two tubes as they are readily available and very economical. I have built my own structures for suspending them above the plants by chains so the fixtures can be moved up and down as needed. Store bought structures are also available. While a single two tube fixture is marginally effective, I like to use two fixtures for a total of 4 tubes. Then for added effect I may also place reflective panels on both sides of the seedling trays. This would be most helpful when there is no natural light available.

Light intensity is very important. As you move away from the tube, light intensity falls dramatically. In fact doubling the distance decreases light intensity by half. For good stout transplants, place lights about 2 to 3 inches above the seedlings. Raise them as needed to allow for the growing seedlings.

Leave the lights on for about 16 hours a day if there is no natural lighting. Inexpensive timers that turn the lights on and off are helpful and can be purchased at a local hardware store.

A final word about lighting. Florescent tubes decline in output over time. While they may continue burning for many months, most experts say they need to be replaced after six months to keep light quantity and quality at a high level.


Various species have their ideal temperatures for germination. If conditions are a little warmer or cooler it simply may delay germination a little. However in most cases room temperature is adequate and a bit warmer is even better. Gardeners have long known that to set a seeded tray on top of the refrigerator where temperatures are a bit warmer helped them get off to a fast start. If you do this just check them daily so you can move them to a well lit location immediately after they germinate.

Another option is to purchase a special heating mat to set trays on for seed starting or for rooting cuttings. With such a mat you can start seed even in a semi-protected outdoor location such as a cold frame or unheated greenhouse.

Warm temperatures promote fast growth. This can lead to lanky seedlings and as such a more moderate growing location may be best for most seeds. When time allows I like to move seedlings outdoors during the warmer part of the day where light is good but the air still cool in winter, and then back indoors in the evening. Just don’t expose them to bright light suddenly or you can burn their tender leaves which are accustomed to much dimmer conditions.


Like temperature, nutrition is good in moderation. Germinating seeds have their own built in food supply. Growing seedlings will benefit from a very diluted dose of liquid fertilizer solution. If you push them with too much nitrogen they can become lanky instead of strong and stout like you want them to be.

If you use a standard soluble plant food go with the low “constant feed” rate, starting when the plants have their first true leaves. Diluted fish emulsion and seaweed also works very well for growing transplants.

Bumping Up

When seedlings have three to five true leaves they are ready for transplanting into the garden. It is best to time indoor seeding to correspond to the ideal outdoor planting time. Allow two to three weeks for squash and melons, four to six weeks for lettuce and five to six weeks for tomatoes and seven to eight for peppers and eggplant to grow to transplant size.

imageOne exception is spring tomatoes. We have a very narrow tomato production period after the danger of frost is past and before the heat of summer arrives. Therefore it is a good idea to start seeds very early and as seedlings reach transplant size to move them into progressively larger containers to accommodate the growing roots. This repotting is commonly known as “bumping up” the transplants.

By the time the danger of frost has passed, you can have a large plant with blooms and tiny fruit growing in a gallon pot. This gives you a great head start on the season. You of course realize the importance of having the earliest tomato of the season when you stop in for coffee at the liars club meeting down at the local cafe!

Hardening Off

Your transplants will be living the life of Riley in their temperate indoor environment. When the day comes for them to be plopped into the cold soil and subjected to the almost-frosty nights of spring, it can be quite a shock.

It is best to gradually introduce them to their new home. Start by moving them out for a short time each day to a bright but protected area, gradually extending their time outdoors. This process is known as hardening off. With a couple of weeks to grow accustomed to the great outdoors they should be ready for the permanent move to the garden.

Cold Frames

A cold frame is basically a small unheated outdoor greenhouse. There are many styles available for sale or you can easily build your own. A cold frame should have a hinged lid covered with clear plastic or polycarbonate material to allow light through.

The lid allows easy access to plants and can be propped open on warm sunny days.

Cold frames are great for hardening off transplants or even for growing hardier seedlings like lettuce and cole crops. With a heating mat designed for starting seeds they can be used all winter long here in the south.

Growing a few of your own transplants is really not that difficult. There is no better way to get the latest varieties and it is really a lot of fun too. Give it a try this season. Garden centers and mail order sources offer many handy gadgets from seedling trays to heating mats and light fixtures to help you along. Raising transplants is also a great way to beat those winter blues with a little optimistic step of faith that gardening season has already begun again.

Subscribe today!