Fertilizing

July 28, 2018

In a recent article, you talk about fertilizers, and how you need to fertilize frequently for plants in containers.  Is it OK to use regular dry fertilizer granules, or do you have to use a solution?

You can use either a dry granular fertilizer or a water soluble one.  The key is to use it lightly when it is this hot and dry.  Make sure with either type you water well.  For the granular forms, keep it off the foliage and water after applying.  With the liquid forms, water the plant first and then use the water soluble solution.  If the plant is too dry it can get burned. 

(November 2011)

I have two five foot tall hibiscus plants which I have brought inside. Their trunks are composed of 3 to 4 intertwined branches and they seem to be healthy. A recent article of yours said these should be cut back 50% when I put them back out in the spring.  My plants seem more like a tree than a plant.  Should they also be cut back this severely or somewhat less than your suggestion?

Tropical hibiscus plants bloom on new growth.  If you don’t cut them back, they don’t grow as quickly and you don’t get as many flowers.  Since yours have braided trunks and have been tree-formed, you will not cut into the  trunks, but you will want to severely cut the network of branches at the top of the braided trunk. I would also suggest repotting it when moving it back outside next spring.  Both pruning and repotting should encourage new top growth, which should result in constant flowers.  Don’t forget to fertilize at least monthly once outdoors as well.

(December 2011)

I have two hibiscus plants in pots that I have brought in to the house for the winter.  When should I prune these?  How much should they be pruned and should I fertilize them?

I would suggest pruning them back by at least half in late February through mid March.  You could also wait until you move them back outside, but then the recovery could be a bit slower.  Usually by late February, the day length is getting longer and the plants have gotten used to indoor conditions, and they begin to put on new growth.  A light application of fertilizer can be put on when you see the new growth.  Wait until April to move them outdoors, and then fertilize every two weeks or so.  They bloom on new growth, so you need to encourage that by repotting, fertilizing and cutting off old wood.

(July 2010)

I have some petunias planted in urns and a hanging basket. They all have grown over the edges and are hanging down, which would be beautiful but they are looking ugly and woody. Is it the hot weather?  Should I trim them back, if so how much?

If the hanging baskets aren't large, this often happens to petunias with hot weather. I think they often do better for home gardeners in the ground.  They need a lot of fertilizer in containers to keep full and healthy.  Petunias are heavy feeders in any situation, but we water pots so much that we leach out the nutrition quickly.  Weekly applications of a water soluble fertilizer are needed for petunias in pots to look good.  Cut them back by half or if the ends look good, add some more plants to the top of the container to fill in there.

(April 2009)

I would like to try growing a tomato plant in a pot this year. Are there any special techniques I should try?  What about the soil?  What mix should I use? This will be new for me, as I've grown Big Boy in the past, in a small sunny area in my back yard. I had the idea from a co-worker that has limited space because of apartment living.

Tomatoes are easy to grow in containers, but give yourself a break by planting them in large enough containers that they don’t need constant water this summer.  A minimum five gallon sized pot is best.  Buy a commercial potting soil, instead of using garden soil.  Garden soil tends to be much heavier and can contain contaminates like weed seeds and insect larvae.  If the site is in full sun, you may want to add some of the water absorbing polymers in with the soil to help it retain moisture.  Some potting soils come with these already added, but regardless, don’t get carried away with them—a little goes a long way.  You can grow indeterminate varieties like Big Boy, and use tomato stakes or cages just like in the garden, or you can grow the “patio” types which are really determinate varieties that have a stronger stem but limit the length of time you harvest.  Fertilize at planting with a slow release fertilizer then fertilize about every two weeks with a water soluble fertilizer.  You will need to fertilize tomatoes grown in containers more often than those in the garden, because you are watering more often, since container soils dry out quicker due to smaller volume and elevated status.  Watch for insects and diseases, but diseases are usually less of a problem because you are starting with fresh, sterile soil each season.  Mulching the pot after planting will also aid in moisture retention.  As with any tomato, give them a site that gets at least 6-8 hours of sunlight.

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