ABSTRACT

Like most things in life, if you want to be successful you must start out laying the basis for success at an early stage� Growing plants is similar� You must start with the healthiest, most vigorous seedlings to get healthy, productive plants as they mature� There is a phrase in agriculture that states: “Start with a good seedling to achieve a healthy plant; start with a poor, weak seedling to end in a significantly less productive plant�” Optimum environmental conditions will greatly influence the health and productivity of the crop� Important factors that influence seed germination include temperature, water, and oxygen, all of which are important to initiate rapid growth and development of the embryo in the seed to begin a healthy life of the seedling plant� Most seed catalogs give you information on the optimum temperature ranges for seed germination� They often provide preferences of the soil conditions and light for optimum plant growth� Follow those tips closely� Soil conditions generally refer to drainage, which directly influences oxygen levels for seed germination and subsequent growth� The type of substrate plays an important role for the best germination of seeds as it must have adequate moisture retention, but at the same time provide good aeration as oxygen is needed in the germination process� With hydroponic substrates, these oxygen levels will be provided by all substrates, however, for higher moisture retention you can use a peatlite or coco coir medium, whereas more “well drained” substrates refer to vermiculite, coarse sand, and perlite�

Always observe the percentage germination given on seed packages to determine how many extra seeds to sow to get the correct final number of plants� For example, if the germination test indicates 85%, multiply the inverse of that number times the final number of plants (e�g�, 30 plants) required (100/85 × 30 plants = 35 plants)� It is also a good practice to sow at least 10% more seeds than you need for transplanting as that allows you to select the best seedlings for transplanting and growing on� Using this example then, (35 + 10% × 35 = 39) sow 39 seeds� The number of seeds to sow per growing cube or tray cell varies for different crops, especially herbs that are sown in clusters or bunches� Some seeds, such as lettuce, are available in both raw form and in pelleted form� In some cases, seeds may be purchased as clusters or as primed seed to facilitate sowing and improve germination� In the presentation on individual crops that follows, a guide is given for the number of seeds to sow per cube�

Arugula seed is fairly small with a seed diameter of about 1 mm (about 1 32″)� This small seed is difficult to accurately sow a specific number of seeds� Some seed companies make seed clusters of about 12 seeds stuck together with a water soluble

adhesive� Usually about 10-12 seeds per cube are the correct density� Alternatively, the seedlings can be thinned upon germination by cutting the extra ones off near their base with a scissors� Be careful not to damage the ones to be kept when thinning� Sow the seeds in Oasis or rockwool cubes (Figure 23�1) or in a peatlite mix in 72-celled compact trays� In pots or beds of peatlite substrate sow the seeds directly into the containers� If you wish to transplant from cubes to nutrient film technique (NFT) or raft culture do so 14-18 days after sowing the seeds�

Optimum temperature range for germination of arugula is 65-75°F (18-24°C) and pH between 6�0 and 6�8� Most vegetable crops like a pH from 6�2 to 6�5� Germination takes from 5 to 7 days� Use raw water for the first 7 days until they reach about an inch high, then use a half-strength nutrient solution until transplanting� They like full light to partial shade� It takes about 3-4 weeks to first harvest and can be harvested two more times thereafter at 3-4-week intervals� As the plants mature they become bitterer in flavor so it is best to replace them after three cuttings�

Sow bok choy in rockwool or Oasis cubes and transplant them to NFT, raft culture, or plant towers at 21-25 days� Sow one seed per cube or if more, thin them to one plant at 12 days of age using a scissors when they are about ¾″ high� Geminate the seed with raw water for the first 8 days, then a half-strength nutrient solution until transplanting� Optimum germination temperatures are between 75°F and 83°F (24-28°C)� The round, black, bok choy seed is slightly greater than 1 16″ in diameter and therefore is easier to handle than that of arugula�

Lettuce, as I am sure you are aware, is a cool-season crop, so lower temperatures are more favorable for it� Temperatures from 60-65°F (16-18°C) are best for germination and growth� The lettuce seed can become dormant at high temperatures, especially above 68°F (20°C)� Using pelleted lettuce seed expands the temperature range for germination by overcoming dormancy induced by high temperatures� Keep pelleted and raw lettuce seed cool and dry in a refrigerator and use it within a year, especially pelleted seeds� For indoor and greenhouse growing use heat-tolerant varieties that are resistant to bolting (going to seed) and tipburn (browning of outer edges of leaves)� Varieties having these qualities are listed earlier in Chapter 22�

Start lettuce in Oasis or rockwool cubes� I prefer rockwool cubes as they do not break apart as easily as Oasis during transplanting, especially in raft culture where it is crucial for the seedling cube to remain intact as the cubes are squeezed a little to fit into the planting holes of the boards� We are fitting square cubes into round holes of the boards� The principle of square pegs in round holes applies here� With some NFT channels, the holes are square and the cubes fit with little effort� The seedlings should be transplanted at 18-21 days of age to their production boards or channels�

Here is a procedure to increase the production efficiency of your growing system by the use of two transplant stages� With a raft culture system use a 2 ft × 4 ft board containing 72 seedlings (six rows of 12 plants) and transplant the first time at 10-12 days as the seedlings reach their third true-leaf stage� Depending upon how many plants you are growing, you can reduce the size of this first-stage transplant to 2 ft × 2 ft with 36 plants� A rule-of-thumb is that the nursery area should be about 20% of the overall system� The seedlings are transplanted to their second-stage (final production) boards at their fourth true-leaf stage (about 18-21 days from sowing) or 8-10 days from the previous transplanting� At this stage there are 18 plants (three rows of six plants) per 2 ft × 4 ft final production board� The lettuce will be ready to harvest within another 24-30 days making the total cycle about 45 days from sowing�

With NFT the procedure is similar� Plants are seeded in Oasis or rockwool cubes (stage 1) and are transplanted for the first time in special nursery NFT channels that have plant holes at 2″ within the channel and channels are separated at 4″ center to center� A 12-ft channel fits 72 transplants� Again, proportion the nursery trays at 20% of the overall production capacity� Start the seedlings in 1″ rockwool cubes (200 cubes/pad) or Oasis 1 “thin cut” Horticubes (276 cubes/pad)� Grow these seedlings in the trays on the propagation bench for about 18 days before transplanting to the nursery channel(s) (stage 2)� Keep them in the nursery channel for about 10-12 days (28-30 days from sowing) before transplanting them to the finishing channels (stage 3)� Within 20-25 days harvest the mature lettuce from the growing (finishing) channels giving you 14 crops per year� In effect, the lettuce only occupies the production area for 20-25 days; that is efficiency in the use of your growing space! Of course, the final production period depends upon the amount of light and day length� This will vary somewhat for a backyard greenhouse due to the season� Using supplementary lights to extend the day length to 14 hours should greatly assist in achieving shorter production periods�

Germinate the seeds as for lettuce between 60°F and 65°F (15�5-18°C)� These salad mixes are directly seeded into beds of a peatlite or coco coir mix as outlined in Chapter 22� Harvest within 3 weeks cutting the top shoots with a scissors or electric knife� Allow 3 weeks or less between harvests for re-growth of the leaves� This harvesting can be repeated several times for a total of three harvests between crop changes�

Basils germinate very quickly, usually within 4-5 days at temperatures between 75°F and 80°F (24-27°C)� Use any well-drained substrate such as a peatlite or coco coir mix if growing them on in peatlite beds or containers� They also germinate and grow well in rockwool and Oasis cubes if you wish to transplant to an NFT or raft culture system� Once the first true leaves appear start using a half-strength nutrient solution to feed them� Transplant seedlings to the final production area after 18-21 days, once they are 2½–3″ tall with at least three sets of true leaves (Figure 23�2)� The first

harvest should take place approximately 7-10 days after transplanting to force the plant to form multiple lateral shoots as was explained in Chapter 22� I have found that sowing 3-4 seeds in a plug or cube to transplant within 3 weeks gives a good cluster of basil plants� Space them about 6″ × 6″ in the production area� Spacing them similar to the lettuce will permit their developing rapidly into a bushy form of multiple stems� Do not allow them to flower unless you specifically want the flowers as this maturing of the plants causes them to become woody� Regardless, rotate the crop every 3 months when making multiple harvests� Otherwise, for a single harvest, as is usually the case for NFT or raft culture production, remove the plants when they reach 6-8″ in height�

Details as to the number of seeds to sow, germination time, and days to maturity of herbs are presented in Chapter 22 when evaluating the best varieties for indoor culture� Best germination temperatures for most herbs lie from 65°F to 75°F (18-24°C)� In my experience with growing them in tropical climates, they will tolerate fairly high temperatures, up to 85-90°F (29�5-32°C) under greenhouse conditions� Do not hesitate to grow most herbs under fairly wide temperature ranges, they will survive� Again, I highly recommend planting herbs in plant towers with a peatlite, coco, or perlite mixture as production is greatly increased through training these low-profile plants in the limited space of your home or backyard greenhouse�

With slower to germinate herbs such as thyme and rosemary, start them in rockwool or Oasis cubes and transplant thyme after 6-7 weeks and rosemary at 8-9 weeks� Figure 23�3 shows thyme in Oasis cubes at 30 days that is almost ready to transplant to plant towers�

Eggplants, tomatoes, peppers, and cucumbers are vine crops so seeding and transplanting are similar, with some specific differences� Seed eggplants in 1½″ rockwool cubes� Place one seed per cube� Be sure to thoroughly flush the rockwool cubes with raw water of pH from 6�0 to 6�5 prior to sowing the seeds� This will adjust the pH of the cubes and completely wet the cubes throughout� You do not need to cover the seed holes of the cubes as long as the RH is maintained at least at 75%� Water the cubes several times a day with raw water for the first 8-10 days as the seeds germinate within 6-8 days (compared to tomatoes that take 3-5 days to germinate)� Germination temperature is similar to tomatoes at 75-78°F (24-25�5°C)� After 10-12 days, replace raw water with a half-strength nutrient solution� Separate the cubes and double the spacing after 10 days laying them on their sides� This side position adds to rooting when transplanting to the rockwool blocks at 14-21 days for tomatoes and eggplants (Figure 23�4)�

Eggplants initially are slow in growing, but once transplanted to the rockwool blocks, they begin to grow much faster� Space six blocks per mesh tray flat in a checker-board configuration to maximize distance among the plants (Figure 23�5)�

Eggplants are held in the rockwool blocks in trays for a period of 4-5 additional weeks making them 6-7 weeks from seeding before transplanting to the final production system (Figures 23�6 and 23�7)� This propagation period is several weeks longer than for tomatoes� Of course, the exact time is dependent upon temperature and light conditions� Be sure to keep the temperature of the medium and nutrient solution at 75°F (24°C) as cool temperatures will slow root growth and overall development resulting in a weak plant� Refer to Figures 23�4 through 23�7 to see the transplanting and subsequent growth of seedlings ready for final transplanting to the growing system�

Various seeding cubes, trays, and transplanting blocks are shown in Figure 23�8�

Initial sowing of seeds and propagation is similar for both European and Beit Alpha (BA) cucumbers� Sow one seed per 1½″ rockwool cube after thoroughly moistening the cubes as described for the eggplants� Beit Alpha cucumbers are started and produced under the same conditions as for the European (Dutch) types� Optimum germination temperature is 75°F (24°C)� They will germinate within 2 days� Keep

the temperature of the cubes at 73°F (23°C), but do not worry if this is not exact, just maintain temperature within a few degrees of this to get vigorous root growth� If using artificial lighting (indoors) use a 14-18-hour day regulated by a time-clock�

Do not lay the seedlings on their sides as is done with eggplants, tomatoes, and peppers� Just space them to double once the cotyledons (initial seed leaves) are fully expanded and you can see the first set of true leaves forming in the center� Within 7 days, as the first set of true leaves expand to a little longer than the cotyledons, transplant them to the rockwool blocks� Use a dilute half-strength nutrient solution to water them after the first week� Thoroughly flush the rockwool blocks with a half-strength nutrient solution to adjust the pH between 5�8 and 6�2 before transplanting the seedlings to the blocks� Space seedlings at six blocks per mesh tray as for the eggplants� Transplant the seedlings to the final growing area when they are 18-28 days old and have 3-4 true leaves as shown in Figure 23�9� This age depends

upon the temperatures and seasonal sunlight (in a hobby greenhouse) or supplementary lighting indoors�

Cultural techniques for growing BA versus European cucumbers differ in spacing and training, as discussed in Chapter 24�

Once again, as with the other vine crops, use the same size of rockwool cubes and prepare them with raw water as outlined earlier� Sow one seed per rockwool cube� Peppers like somewhat higher germination temperatures than eggplants, cucumbers, and tomatoes from 77°F to 79°F (25-26°C)� Keep these temperatures day and night�

Maintain relative humidity (RH) from 75% to 80%� Once the seeds germinate (about 4-6 days) lower the air temperature to 72-74°F (22-23°C)� Provide supplementary lighting of 5500 lux (510 ft-c) with 18-hour day length�

Within 10 days after the first set of true leaves have expanded slightly longer than the cotyledons, lay the peppers on their sides as you double space the cubes in the mesh trays� Peppers grow slower initially than cucumbers and tomatoes� Transplant the seedlings to 3″ rockwool blocks at 3-4 weeks from sowing� Prepare the rockwool blocks with dilute nutrient solution as described earlier for cucumbers and space them six to a mesh tray� When transplanting to the blocks lay the seedlings on their sides in the large round holes of the blocks� By placing your thumb next to the top of the cube while pushing it into the block you can protect the pepper seedling stem from breaking as shown in the photo for the eggplants (Figure 23�4)� Air temperatures during this stage should be about 73°F (23°C)� The seedlings will be ready to transplant to the final growing area within 3 weeks from putting them in the rockwool blocks (between 6 and 7 weeks from sowing)�

Soak the 1½″ rockwool cubes as with the other vine crops and sow one seed per cube� Use raw water of pH 5�5-6�0 to lower their pH� There is no need to cover the holes of the cubes after sowing� Always adequately water the rockwool cubes and blocks to prevent their drying� Usually several times per day is fine� Regulate temperatures from 77°F to 79°F (25-26°C) day and night during germination� They will

germinate within 3 days� Once the cotyledons are fully expanded and the first set of true leaves are 1″ long start using a dilute nutrient solution as was done for the other vine crops� At this stage reduce the temperature regime to 73°F (23°C) during the day and 68°F (20°C) at night�

Lay the tomato seedlings on their sides as they are double spaced in the mesh trays at 10-14 days from sowing� Once the true leaves are fully unfolded (about 3 weeks after sowing) transplant them to the 3″ rockwool blocks being careful to soak the blocks as for the other vine crops and placing the seedlings on their sides into the blocks� Placing them on their sides will promote adventitious roots to form along the buried portion of the stem base as with the peppers and eggplants (Figure 23�4)� This increases the number of roots resulting in stronger seedlings� Arrange six blocks per mesh tray in a checker-board pattern as for peppers and eggplants (Figure 23�5) to give them sufficient space so that their leaves do not overlap as they continue expanding� They will be held in the propagation area for another 3 weeks before transplanting to the production system at an age of 5-6 weeks from sowing of the seeds�

Whenever seedlings are transported to other areas within the propagation location or transferred to new trays, these facilities and growing trays must be sterile� Clean all of these with a 10% bleach solution prior to bringing the seedlings in contact with such items� Likewise, when soaking the rockwool cubes and blocks do it in a clean sink to avoid any contamination� Small precautions like these will go a long way in your successful growing of seedlings�

In soil gardening such cleanliness is not possible; this is a great advantage of hydroponic growing to produce plants free of diseases� It is not difficult and contributes greatly to your success!