Polyembryonic Seeds

Plants grow from seeds, but what many people do not know is that not all seeds contain just one plant embryo. Many varieties of mangos, for example, have polyembryonic seeds, as do most citrus.

A polyembryonic seed is one which contains multiple embryos. Poly-embryonic seeds produce a number of shoots, one of which originates from fertilisation. The fertilised seedling is often weak and stunted and should be discarded. The other seedlings are clones of the mother tree. Yes, clones – just like a cutting, only from seed.

This means that if you grow a polyembryonic mango (such as Kensington Pride or Bowen, which is pretty much the only variety that we can buy in supermarkets in WA) or citrus (Valencia orange, Lisbon lemon, West Indian lime, Thompson or Marsh grapefruit, Murcott, Kara mandarin, amongst others) variety from seed, it will be true to type. If only the same were true of stone fruit and grapes – although even there, there aren’t really many genes left that aren’t for amazing delicious fruiting capacity, so it’s worth trying to grow those from seed too. You might get a gorgeous new variety, or something very close to the parent.

Back to mangoes.

I have one mango tree, about two years old now and planted out in the ground, which I grew from seed. Mostly by accident to be honest – I put the mango pip in the worm farm, and a month or so later when I emptied that level to put some worm castings into a garden bed, the seed still hadn’t started to decompose. It had, in fact, sprouted. So I planted it in a pot with some worm castings and potting soil, and watered it every day, and it turned into a tree.

Mangoes are really very easy to grow. The recommended process is to keep the seed after eating a mango, and remove as much flesh as you can, then let it air dry for a day or two (in dry weather, such as we often have in Perth, probably err on the side of less drying time, or dry it in a humid environment like a worm farm). You can plant the whole seed in a warm, moist place and wait for it to sprout – at which point you remove all but one of the seedlings, or gently separate them and grow them all on individually. Alternatively you can separate the embryos out to plant individually; to do this, you have to very carefully open the mango seed. Cut a small corner off the seed, and then break it open. You should see several small, bean shaped seeds, which should be white (ratehr than grey and shriveled, which would mean that they’re not viable). Plant each of these bean-shaped seeds in a warm, mopist place; they should sprout in about ten days. The same technique works with citrus seeds, but they’re smaller so you have to be more careful if you want to separate the embryos out to plant individually.

The Ag Department says that there are three varieties of mango available in WA: the Kensington Pride (polyembryonic), R2E2, and Edward. Other varieties suitable for the Perth area include Haden, Namdok Mai, and Kent. Seedling trees should produce their first fruit at 3 – 4 years old, but will not produce a good crop until they are around 7 years old. Young trees can be killed by frost or cold weather, so don’t plant them out until they’re at least a metre tall.