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Garden Help Desk: Home gardeners face different hurdles than commercial growers

By Usu Extension garden Help Desk - | Jan 31, 2021
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Once seedlings have a first set of leaves, they benefit from regular applications of 1/4 to 1/2 strength fertilizer.

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A stocky, healthy seedling comes from providing all the right conditions- good timing, bottom heat, and bright light.

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It doesn't take a very big footprint to assemble all the essentials for growing healthy transplants.

Question: The last 2 years, I’ve been able to start flowers and vegetables under a grow light with a heating pad until it’s time to move them out. They germinate within seven to 10 days and in 6-8 weeks they are 6-8 inches tall, and I’ve put them outside when I also start fertilizing them.

They’ve grown fine but are always spindly and take a while to bloom. How do the greenhouses have them in bloom when I buy them in May?

Answer: Sturdy, productive transplants need a few things — a seed-starting date scheduled according to the needs of the species; steady, uniform bottom heat during germination; bright light for at least 11 hours per day (this depends on the species, most need 12 or even 15 hours); good air circulation; and even watering without overwatering or drought stress.

Read all the information on your seed packets for details about your particular varieties need. Decide when you’ll be putting your plants our in your garden and use the information on your seed packet to count back from your transplant date to determine when you should plant your seeds.

Remember, every species is different, so you probably won’t be able to start all your different plants at the same time.

You’ll have better results if you invest in one or two seedling heat mats plus a thermostat for steady, even heat. Your goal is to maintain about 72-80 degrees in the daytime for the most common vegetables.

If you have a way to reduce the temperature by five to ten degrees during the night, even better. Most species will do best with reduced heat or no added heat beginning few days after germination. Check your seed packet or look at an online germination guide to learn what is best for your seedlings.

Using a plastic dome over your planting trays during germination will help to provide even temperatures and humidity, but a simple layer of plastic wrap will be better than no cover at all. Lift the cover at least once a day, and remove the plastic cover completely once you see that at least half of the seeds have germinated.

Once the very first seeds have germinated, it’s time to provide your seedlings with bright light, if you haven’t already been using lights.

Light from a bright south- or west-facing window won’t do the job; you need to supplement with LED grow lights or very bright fluorescent lights placed just a few inches above your seedlings. Bright light is very important if you want to prevent thin, leggy transplants with weak stems.

When your seedlings have at least one set of true leaves they will benefit from one-fourth to one-half strength fertilizer applications.

Don’t worry about your home-grown transplants not being in bloom when you’re ready to plant them out in the garden; that’s perfectly normal and natural.

Commercial greenhouses can do a few things to stimulate flowering that wouldn’t be practical for the home gardener to try. In addition to careful timing for their seed-starting, greenhouses are careful about temperature control during germination and during “growing on.”

A greenhouse can manipulate the day or night lighting and the day or night temperature differences, and they may also use plant hormones to produce transplants that remain short while also being in bloom.

If you’ll pay attention to the basic details — planting each species or variety at the right time, plenty of bright light, the best temperatures for the plants you’re growing and good plant nutrition — you’ll come pretty close to what you see in the commercial greenhouses and nurseries and have good flowering within a few weeks of transplanting.

Question: I planted an apple tree 2 years ago for the first time, and I think there will be some fruit this year. What is the best way to protect my little tree from fire blight right now?

Answer: Erwinia amylovora, the bacterium that causes fire blight, isn’t active during cold winter weather, so there isn’t spray or special treatment you need to do right now to protect your tree from. You can take advantage of this late-winter time to do your pruning while there isn’t any active bacterial oozing and your pruning cuts are fresh.

There are some protective sprays that may be helpful during bloom, but the most practical method for home orchardists is to watch your apple and pear trees after petal fall and prune out any flower clusters that look dry, shriveled and blackened or brown. Removing those infected blossom clusters will remove the bacteria before it can move farther into the tree.


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