Any advice about when to fertilize in spring. I currently plan to wait until mid March as I am worried about late freeze damage. Location is League City area - zone 8b Texas.

Additionally, does anyone know the hardiness of mandarinquat and/or bloomsweet "grapefruit"?

I cannot give an exact date to fertilize as I do not know the average last date of frost in your area. However, it is best to begin fertilizing just before growth initiates in the spring. This will greatly assist in the bloom of your tree. Bloomsweet Grapefruit hybrid (Kinkoji Grapefruit) is listed hardy to 10F (-12C) when fully dormant. Not sure on Mandarinquats, however kumquats are hardy to about 15F (-9C) and mandarins to mid 20s. Mandarinquats would be somewhere in the middle. Perhaps another member knows exactly.

Millet
Robert Southwell

I would apply fertilizers during the last rainy days in our area about 2 weeks before spring. In your case, you will have to take note when your flushes starts each year, apply fertilizers about 1 to 2 weeks before that. Late season frosts will happen anyway, whether you applied fertilizer or not. The fertilizer that you applied are not taken up immediately nor are processed when the trees starts to awake. It is the nutrients that are stored in the stems that are used first, and only after about 1 to 2 weeks of growth, then those nutrients from the soil will become useful, and so that is how I timed my application. As to how much time before stored nutrients are depleted, a lot of factors can come into play like how big are your trunks, the roots, how active the plants are, how warm it is, what cultivar type (ie, satsumas are generally slow growers, my clementines usually have later growth flushes, etc.) So my practice is more general compromised method for all my citrus trees as I fertilize them at the same time in late winter.

Bob
You should fertilize now. LSU recommends late January to early February for citrus. You are as far south as I am so you are probably in bloom now.
Karl

Thanks. I did not take into consideration that it would take a while for the trees to absorb the fertilizer. I will go ahead and fertilize for the spring.

The only citrus currently in bloom is meyer lemon.

I would wait until mid-march. That is the average last frost for Beaumont anyway. You won't gain much by doing it now, but will expose yourself to dangers of a late freeze. You might remember the March 19th hard freeze of 19F we had a couple years ago. You don't want your tree growing for that. Indio mandarinquat should be pretty hardy, about like an orangequat as the heritage is identical and mandarins and kumquats are relatively hardy as they are the parents. I grow my indio mandarinquat in a pot as I don't want a whole tree of those very sour fruits. Bloomsweet (other names are citrus obovoidea or kinkoji I think, but correct me if I am wrong)has been reported to be hardy, but I'd rather have a better tasting grapefruit that I have to protect than a hardy inferior one. I grow golden grapefruit but am giving bloomsweet another chance by grafting a limb. I haven't had a bloomsweet I liked before. However, as always the hardiness of the tree depends on the individual amount it is dormant. I have three trees in a row all 3 years in the ground and about 4 feet tall, clementine, fairchild mandarin, and orlando tangelo, planted the same time and all on flying dragon 8 feet apart. One of the frequent freezes we had this winter defoliated the orlando tangelo and left unharmed the other two. During another freeze a few years ago, my meiwa kumquat was killed while the satsumas were undamaged. Biggest factors to cold hardiness on the Texas Gulf coast are the weather preceding the freeze and how late you fertilized the tree, and chance I am convinced If you fertilize after July 4 you are asking for your tree to be growing the next winter during the freezes=>less cold hardy. Cold hardy is another story in northern California where the weather is consistently colder but not freezing for longer in the winter. Here in the Houston area we frequently have 80F one day and sub freezing the next day=>this takes away the cold hardiness of citrus trees.

Go to lsuagcenter.com, the pull up home citrus production. This is the best information you can find on fertilizing and spraying citrus. If I remember corrctly the time to fertilize is the end of January and then 45 to 60 days later. do not fertilize after the first of June.
Take Care,
bonnie childers

I read the LSU recomendations and went ahead with fertilizing mine. That article, however, made me think that the fertilizer does not stimulate growth (in the sense of initiating it), since even in So. LA, mid Jan is subject to some frosty mornings.