Q/A column – for release October 29, 2008

Dan Culbert - Extension Horticulture Agent 

 How Does Your Garden Grow? 

Greenhouse Vegetables

What are the best vegetables to grow in a greenhouse? What is the best soil to use for planters in a greenhouse? -  Steve -

Almost any kind of vegetable can be grown in a greenhouse, but as space is often limited, choose those that can be staked, vining plants that can trained to a trellis or those that are able to stand up on their own.  Plants that provide a continuous crop are also a better choice that ones that are completely harvested. 

Also consider how long it will take to grow the crop to maturity.  Long-season plants may be an inefficient use of expensive greenhouse space.

Popular greenhouse plants could include tomatoes, peppers, cucumbers, pole beans and peas plus most herb plants.   Among those that would take up a lot of space but give limited amount of produce would be sweet corn, sweet potatoes, and watermelons.

Almost any vegetable can be grown in a greenhouse, but in our area, equal gardening success at a reduced cost can be done outside.  Cool season plants like collards and other cole crops will make it through all but the most severe hard freeze.

The best greenhouse soils would be the artificial soil mixes found at garden centers.  See the UF Bulletin “Mini-gardening” (http://edis.ifas.ufl.edu/VH032 ) for more hints on selecting plants and container soils. 

Also see: Hochmuth, G. Irrigation of Greenhouse Vegetables [HS768]. UF/IFAS Extension Service, 2/08. http://edis.ifas.ufl.edu/CV264 

Vegetable Fertilizers 

What is the best fertilizer for vegetables? I was told that it was best to use composted cow manure.  How do you know when to fertilize vegetables? - Charlie -

Fertilizers used in the vegetable garden can be either slow release or quick release.  The amount applied and the frequency will be much different depending on which is used.

Slow release fertilizers are often called “organic” fertilizers, and are usually a more expensive form of nutrients.  Before being absorbed, they must be changed into soluble forms that can be taken up by the plant roots.  They are often added to garden bed soils when planted, and a supplemental “side-dressings” may be added throughout the crops growing season. 

Quick release nutrients are often in-organic forms that are ready to be taken into the vegetable plant, but they also can be washed out of the soil if there is too much rain (or irrigation).

Composted cow manure is an organic source, but the relative amount (called the analysis) of nutrients is often quite low.  Most vegetables will need more than just cow manure as a nutrient source.  Organic material is quite valuable to the vegetable garden, however, as it serves as the “glue” that helps to keep fertilizers and beneficial soil organisms in place. Compost is another great source of organic material.

I’d recommend that a combination be used:  apply the granular organic forms at planting, then use dilute solutions of soluble fertilizers as the seeds or plants start to grow,  and follow-up with side dressings of additional granular fertilizers if needed.  Check the results of your soil test or review the Florida Vegetable Gardening Guide (http://edis.ifas.ufl.edu/VH021) for the exact amount needed per foot of garden row.

Watering Small Vegetable Plants

 Do young vegetable plants started from seed need to be watered every day? How much - just a sprinkle?  When is the best time to water plants - In the mornings or evenings?  What does it mean when leaves turn yellow on vegetable plants? - Tim-

When growing vegetable transplants or starting them in the garden, check the seedlings every day to see if they need water.  Use the finger test: stick your finger into the soil to see it if feels cool.  If it is, it is probably moist enough; if it feels dry, it will need water.  Then don’t water again until it feels dry.

The amount to water will depend on the size of the plants and how much rain has recently fallen.  Right now, ½ to 1 inch of rain or irrigation per week would be more than enough.  Best time to water plants is in the morning; that way if the plants get wet, the y will dry off before dark. Wet, dark plants are more likely to rot.

If all the leaves are turning yellow, it can mean that the roots are waterlogged or maybe affected by a soil born fungi.  It could also be a number of other issues like a lack of fertilizer.  If it’s just the bottom few leaves, it may be a normal leaf loss as new leaves shade out older ones.  Bring us a picture or a whole plant if you have several plants to spare.

 Small seed spacing

How do you plant tiny vegetable seeds without getting them too unevenly distributed?  Last year all my carrots came up bunched together and I really had to thin them. - Teresa -

 There are some companies that sell “seed tape” where seed are spaced out at the proper distance. Others make pelletized seed – little “pills” that are easier to handle.  However these are expensive ways to insure proper seed spacing. 

I like to carefully open a corner of the seed pack and lightly tap my finger on the side to let out a few seed at a time.  Another idea is to mix some of the seed with a small amount of coarse builder’s sand or vermiculite, which would then be easer to spread in the seed furrow.   In most cases, thinning of carrot seedlings will usually be needed.