@heirloomgal , you are fortunate to be able to buy seed. I was blessed to have a friend find & purchase 1 kilo of seed for me in a Milwaukee market years ago, and have been growing from that seed ever since. Water spinach (
Ipomoea aquatica Forssk) has been banned here as a noxious weed, so seed sales have been outlawed for years. This is because in tropical climates (such as the Florida Everglades) water spinach can take over & clog waterways. That is obviously not a problem for you & me, where anything tropical floating on water becomes dead & icebound in Winter.
Water spinach is photo-period sensitive, so will not bloom or set seed in our higher latitudes. Unfortunately for seed saving purposes, short of artificially regulating the hours of daylight, that is the bad news.
I have only seen the morning glory-like flowers a couple times over the years, and then only a flower or two in Summer's last gasp.
There are 2 supposed cultivars out there, a "wet land" and a "dry land" (previously listed as separate species, but now combined into
I. aquatica). The "wet" version has bigger & better leaves, but needs to be kept wet, and is more sensitive to water or cold stress. The "dry" version still requires heat to thrive, but can be planted in the garden like any other heat-loving vegetable. I grow the dry land. Honestly, I question whether the two are just phenotypes of the same plant, in response to the growing environment.
In our climate, water spinach grown from seed should be started indoors. The plants benefit from crowding, so I over-sow in plastic cells (72/tray) and allow up to 4 plants per cell. When I grew seed from packets, germination was often spotty (and sometimes zero
) so unless you intend to germination test, I would suggest over-sowing by a 2/1 ratio. The seeds really need warm soil to germinate, so a low of 70F / 22C should be the absolute minimum... and the closer to 80F / 27C, the better. The seeds generally emerge over a staggered period. The seed coat often clings tightly to the emerging sprout; frequent light misting (and sometimes gentle fingers) will help them to break free. The seedlings will then need strong light until it becomes warm enough for them to be moved into direct sunlight.
Water spinach is often sold in Oriental markets, where they are usually bundled as long shoots (possibly was "kang kong", or "ong choi"). They look much like the sweet potato vines to which they are related. If you can find those, it is a good way to sample the vegetable before deciding to grow it. Pinch or cut off the leaves (and the stem end with the last 2-3 leaves attached) and either boil or stir fry those. Set aside the bare stalks, and keep them moist. If you decide to grow these, trim them down to about 6-8" (20cm) and place them in a jar or similar tall container. Add water to cover at least the first nodes on the stems, and place in a warm brightly-lit place. The stems will root quickly. To avoid rot, change the water frequently, and quickly remove any which die.
Whether using seed or rooted stems, my rule of thumb has been to start them about 30-45 days before the warm weather transplant date.
When transplanting, I plant the seedlings or rooted stems in staggered adjacent rows, to form a wide bed. Rows about 12" / 30cm apart, with clusters of 3-4 plants that same distance apart in the row. The pattern looks like:
X-----X-----X-----X-----X-----X-----X
---X-----X-----X-----X-----X-----X-----X
X-----X-----X-----X-----X-----X-----X
3-4 rows wide seems to be the optimal spacing for both dense growth, and ease of weeding & harvest.
View attachment 72941
Harvest the shoots when they begin to reach about 6" or so, leaving part of the stem with at least 1 node. The plants will quickly branch, and grow thicker until cold nights put a stop to their growth. If picked completely, each row will yield 2-4 pickings, depending upon how long the weather remains warm. It is a very productive cut-and-come-again green, where summers are warm enough to grow it (if you can grow okra or eggplant, you can grow water spinach).
*** Important organic pest control tip. If you grow yardlong beans or cowpeas, grow the water spinach adjacent to them. (You can just see the bush yardlong beans on the left side of the photo.) The wasps that are attracted to those when they begin flowering, will also keep the water spinach nearly bug free.
And two more that I'm not super familiar with, 'Amsterdam 2' and 'Tendersweet'. I think I got a 'Nantes Coreless' as well. Sheesh, bought so many carrot packets it's blurring. Nantes seems to be one of the most favored carrot types, since there are so many variations of it. 
seed company offers it so that'll be fun. Been wanting to try it for awhile now, though I'm suspecting it will be like Asparagus Pea, only a short window of time where they are good (read: passable) eating. lol But they look so cool!
