Any low, even numbered (18-19-20 is close enough to even) fertilizer will be fine. I add epsom salt (magnesium sulfate) every 3 months. I fertilize at 1/4 strength once a week after watering.

I suspect that even at 1/4 strength, most of the fertilizer is wasted. Orchids are slow growing and will only use a little. Higher temperatures and higher light will cause plants to need more.

I have been using Miracle-Gro® Tomato Fertilizer on my orchids for years. Common sense. Tomato flowers precede tomato fruits.

Tomato fertilizers generally lack elements other than N-P-K. Some provide calcium and magnesium. I supplement with MSU formulas & Grow More fertilizers to provide the other "trace" requirements.

--Stitz--

I've read where many people use it. In the summer I give my plants one or two shots of it, just for a change of diet. If one can't find orchid fertilizer, it's an excellent substitute.

I hate to be a wet blanket about it but about the only thing to be said for using Tomato fert on orchids is that used per Richards recommendation (1/4 strength) it will do no harm. I can't think of two more dissimilar types of plants than orchids and tomatoes. Tomatoes are grow monsters that need tons of cheap nitrogen and pottassium and phosphorous, the other trace elements will be assumed to be supplied by the rich loam (topsoil) in which these plants are usually grown. Orchids on the other hand are very light feeders and in nature grow in a low concentration but highly complex mix of major and trace elements. Grown in the home in semi-inorganic mixes puts the burden on the fert to supply all those micro-nutrients and thus if one really wants to do their best by their orchids instead of Tomato fert one will look at Dyna-Gro or one of several ferts intended for hydroponic culture of many things, including tomatoes. The key difference being that the hydroponic formula does not assume a micronutrient rich loam but a nutrient poor inorganic mix.

H

I use Miracle-Gro® Tomato Fertilizer at 1 TB per gallon during summer on the orchids--just like their tomato brethren.

Zygopetalum flowers from July through March in a good year!

--Stitz--